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Araji, AA and Stephen Love. "The Benefits of Investment in the Northwest Potato Breeding
Program." [Vol. 77, 391]
The Pacific Northwest (PNW) is the largest area in the U.S. in the production and processing of potatoes. It produces 55 percent of the
nation's potatoes at an estimated $1.44 billion of farm values. This area also accounts for 69 percent of all processed potatoes in the U.S.
with an estimated annual market value of $2.3 billion. The PW produces 44 percent and 36 percent of the nation's table and seed
potatoes, respectively. The Northwest potato breeding research was established in 1984 with federal, state, and private industry funding.
Since it's establishment, the program released several new potato varieties that are higher yielding, better quality and more resistant to
disease than present varieties. The estimated annual gross benefit to the potato industry in the PNW is estimated at over $201.5 million.
The present value of the flow of benefit over 20 years is over $1.2 billion. Total research investment in the program, including overhead is,
$31 million. The benefit cost ratio is 38.97, which indicates that for every dollar invested in the program the potato industry will benefit by
$38.97.
Acunia, Ivette, Barry Jacobsen, Gary Strobel and Dennis Corsini. "The Use of Thaxtomin A (TA)
to Identify Common Scab Resistance in Potato and TA-Glucose Conjugation as a Mechanism of Resistance."
[Vol. 77, 391]
Resistant varieties have been one of the best solutions to common scab in potato. The discovery of TA, produced by pathogenic
Streptomyces scabies, and its important role in bacterial pathogenicity suggested new alternatives to search in the scab resistance
screening techniques and in the mechanism of resistance to TA in potato tubers. This research investigated the correlation between an
optimized true potato seed (TPS)-TA resistance assay with common scab resistance of potato tubers as determined by tuber TA sensitivity
and scab symptoms in field tests; and tested the hypothesis that glucosylation of TA is related to potato plant resistance to pathogenic
S. scabies.
TA seedling screening assay was a useful tool for identifying scab resistant germplasm under homogeneous standard conditions.
Doses of 1µM of TA and exposure time of 7 days did allow distinguishing between seedling progenies from cultivars that vary in resistance
to scab. TA did not strictly select 100% resistant individuals, but it did allow a decrease in the range of population to be tested under field
conditions by approximately 30%. Significant correlations were determined between seedling index of damage by TA and tuber scab
symptoms (R=0.63, P=0.0001; R=0.49, P=0.0001) and between tuber TA sensitivity and tuber scab symptoms R=0.64, P=0.000l; R=0.75,
P0.01). Highly scab resistant individuals were identified, which can be tested for commercial purposes, parent in breeding programs or
source of resistance genes. Glucosylation of TA by S scabies occurs in vitro. The glucose conjugate of thaxtomin A from bacterial extracts
was described as Thaxtomin A-ß-di-O-gluosides (TAG). TAG was 6 times less toxic than TA in potato tubers. Data in this research suggests
a similar mechanism of TA detoxification in potato tubers. Resistant plants inoculated with 14C -TA were able to produce a higher amount
of a radioactive metabolite with an Rf similar to TAG than susceptible ones. We found almost twice as much glucose transferase specific
activity in resistant than in susceptible individuals. Glucose conjugation may be a mechanism of TA detoxification in potato plants and it may
be related to scab resistance and susceptibility in potato plants.
Baer, Debra, Emily Mitzel, Julie Pasche, Neil C Gudmestad, Dallice Mills and Brian Russell.
"Semi-Quantitative Detection of Clavibacter michiganensis subsp. sepedonicus Using a DNA Hybridization-Based Microtiter
Plate Assay After PCR." [Vol. 77, 391]
The speed and sensitivity of PCR-based assays allow shorter turnaround times for bacterial pathogens whose detection would
otherwise require serological assays or culturing of samples. Three primers (3 pairs) were designed to detect Clavibacter
michiganensis subspecies sepedonicus Cms) by PCR based on the previously determined nucleotide sequence derived from
subtractive hybridization. We found the utilization of two of the primer sets (Cms50 and Cms72), either alone or in a single reaction,
provided sensitivity greater than or equal to 82% and specificity values greater than 98%. These evaluations were performed on naturally
infected potato tuber tissue using an enzyme-linked oligonucleotide assay (ELOSA) after direct labeling of PCR products with Digoxigenin.
We found no statistical difference in the detection of Cms infected field samples regarding mucoid or nonmucoid strains of Cms, cultivar
of potatoes, or primer sets. PCR products evaluated by ELOSA provided a 13% increase in positive detection of Cms compared with
the same PCR products evaluated by gel electrophoresis. The PCR/ELOSA method was also compared to the commercial ELISA kit
currently used for diagnostic purposes. The ELISA failed to detect tuber tissue samples infected with nonmucoid Cms strains that could be
detected by the PCR/ELOSA plate capture assay.
Baker, Kathleen M, William W Kirk and Jeffrey A Andersen. "Microclimate Dependent Modeling of
Regional Potato Late Blight Risk." [Vol. 77, 392]
Potatoes are grown extensively throughout Michigan where several agriculturally important diseases, such as potato late blight, are
directly related to canopy microclimate. Disease risk assessment generally occurs on a small-scale basis, often depending on a single
automated weather station. However, lack of access to equipment and pertinent canopy data limits many growers from utilizing this
information in their management decisions. In addition to increasing data availability, larger, regional scale risk monitoring provides
some standardization of microclimatic variables, which can vary extensively even within a single canopy. This study combines data
from in-canopy automated weather stations maintained by the Potato Late Blight Laboratory, the Michigan Automated Weather Network
(MAWN), and other data from the National Weather Service. Relationships between in-canopy and ambient meteorological variables
have been incorporated into a GIS model to create a regional coverage of microclimate variables for Michigan that can be used to monitor
disease risk throughout the growing season. Model Output Statistic (MOS) 60 hour forecast data and Medium Range Forecast (MRF)
data have been included in the model to enable the prediction of canopy conditions up to five days into the future. Daily results are used
to generate management recommendations for growers.
Bamberg, John B, Stepan Kiru and Alfonso H del Rio. "RAPD Comparison of Reputed
Duplicate Populations in the VIR and US Potato Genebanks." [Vol. 77, 392]
The Association of Potato Intergenebank Collaborators (APIC) produced a global inventory of wild potato genetic resources that is
available on the Internet (http://intranet.cip.cgiar.org/ipd.htm, username = "CIP_LIMA\CIP-INTERGENE", password = "user".
This database shows that, in many cases, several genebanks have samples of the progeny from a single original germplasm collection.
The assumption has been that these samples are genetically equivalent, so all the characterization and evaluation data gathered on a seedlot
from one genebank can be applied to all the other "duplicate" seedlots in other genebanks. This assumption was tested by
comparing 25 pairs of reputed duplicates in the VIR (St. Petersburg, Russia) and US (Sturgeon Bay, USA) potato genebanks with RAPD
markers. In 21 of 25 cases, reputed duplicates among genebanks had significantly less similarity than replicate samples taken from a
single population. The average genetic similarity of reputed duplicates was 93%, and the lowest was 81%. Thus, users of germplasm
should be aware that while samples under the same identifier in different genebanks are usually quite similar, they might not be identical.
Bertram, Melissa C Phillip Nolte and Geoffrey A Barrall. "Using Nondestructive Evaluation (NDE)
Techniques to Detect Potato Tuber Defects and Dry Matter Content." [Vol. 77, 392]
Most potato defects cannot be detected without destructive analysis. Previous tests indicated that magnetic resonance imaging (MRI)
could be an excellent tool for detecting defects. Brown center, hollow heart, bruises, tuber greening, silver scurf, Fusarium dry rot, and
wireworm damage have been investigated on a preliminary basis, but further work was required to determine if MRI could detect these
defects on a consistent basis. Harvest cracks, stem end discoloration, Rhizoctonia, and net necrosis were also investigated, along with
imaging healthy tubers. Magnetic resonance (MR) measurements have also been shown to correlate well with dry matter (DM) content, and
this work was continued in an effort to improve accuracy, consistency, and speed. MRI tests gave consistent results on detection of hollow
heart, blackspot bruise, shatter bruise, Fusarium decay, and wireworm holes when compared to destructive sampling. Attempts to detect
brown center, pressure bruise, tuber greening, harvest cracks, stem end discoloration, net necrosis, silver scurf, and Rhizoctonia did not
yield satisfactory results. MR measurements correlate very well with DM content. Further refinement could improve on these results.
Bisognin, Dilson and David Douches. "Genetic Diversity in Diploid and Tetraploid Potato Late
Blight Resistant Germplasm." [Vol. 77, 393]
The selection of parents in a breeding program for disease resistance is critical to establish a broad genetic base and to increase the
probability to identifying superior offspring. The objective of this study was to assess the genetic variability of potato late blight (LB)
Phytophthora infestans resistant germplasm to be used in potato breeding. Thirty-six diploid and 24 tetraploid potato LB resistant
clones were evaluated for their genetic diversity based on isozymes and simple sequence repeats (SSR). A total of 39 allozymes, encoding
11 isozyme loci, and 42 polymorphic bands in six pairs of SSR primers were scored for presence or absence. The germplasm was
clustered based on the matrix of genetic similarities and the unweighted group pair means analysis of the isozyme and SSR data to
construct the dendrogram using the statistical taxonomic program NTSYS. The diploid Solanum species S. berthaultii and
S. microdontum formed two distinct clades. Within S. microdontum, three groups were observed for the accessions
PI 498124, PI 595510 and PI 595511 possessing strong resistance to LB. The tetraploid germplasm formed another large clade, with
S. sucrense in one distinct group. Two other groups were observed. One grouped the cultivated S. tuberosum and
the other grouped the hybrids between cultivated S. tuberosum and various wild species. Based upon the genetic diversity and
the level of LB resistance, S. microdontum and S. sucrense offer the best choice for strong LB resistance from genetically
diverse sources. This potato germplasm with reported late blight resistance should be introgressed into the potato breeding programs
to broaden the genetic base.
Bohl, William H and Stephen L Love. "Observations From Potato Seed Piece Bruising Studies in
Idaho." [Vol. 77, 393]
A series of studies were conducted at Aberdeen and Shelley, Idaho to more closely examine the effects of seed piece bruising on yield
and other agronomic characteristics. Previous studies in Idaho showed that seed handling had a definite negative impact on yield, but did
not measure individual handling components such as bruising and the relationship of bruising to time of damage, post-cut storage
temperature, seed piece size, and seed piece decay. We measured the effects of these factors in six experiments with the Russet
Burbank cultivar during 1992 through 1998. In three of the six studies, bruising seed pieces significantly increased the number of stems
per plant, indicating acceleration in seed aging. In the other three studies there was a trend to have more stems per plant when the seed
pieces were damaged. Bruising seed pieces did not cause a significant reduction in total or U.S. No. 1 yields in any of the studies. There
were nonsignificant trends for yield reductions (due to bruising or post-cutting storage temperatures) in some studies, but not in others.
In one factorial experiment, seed size had a significant impact on yield while bruising did not, nor was there an interaction between the
variables. These studies suggest that the impact on yield of bruising seed pieces is not as great as previously thought and current
recommendations may need to be reconsidered.
Brandt, Tina L, Gale E Kleinkopf and Mary Jo Frazier. "Storage Characteristics of Six Potato
Cultivars." [Vol. 77, 393]
Seventy percent of the potato crop grown in the Idaho is put into storage. The ability to deliver high quality potato crop out of storage is a
critical factor in the acceptability of a new cultivar. In 1998, a program was established to evaluate storage characteristics of new and
potential release potato cultivars for Idaho. Cultivars tested were: Russet Burbank, Ranger Russet, Gem Russet, and Umatilla Russet in
1998-99 and 1999-00, Legend Russet 1998-99 and A84118-3 in 1999-2000. All cultivars were cured and then stored at 5.6, 7.2 and 8.9 °C
for 9 months. Half of the samples at each temperature were sprout-inhibited with chlorpropham (CIPC) at 60 days after harvest. Whole
tuber glucose and sucrose concentrations as well as fry strip color were determined monthly and both before and after CIPC application.
Sprout ratings, lengths and weights were measured monthly to determine dormancy length and sprouting characteristics. In 1998-99,
dormancy length differences of up to 40 days between varieties were observed. Significant differences were observed in glucose and
sucrose concentrations among the varieties at the three storage temperatures. Gem Russet and Umatilla Russet generally had sugar
concentrations and mean fry colors equal to or lower than Russet Burbank. Glucose concentrations and fry color ratings increased in
Ranger Russet after approximately 120 days in storage at 5.6, 7.2 and 8.9° C. Glucose concentrations stayed below 0.1 % fresh weight
and mean fry colors below 1.5 (USDA fry color scale) in Umatilla Russet throughout 9 months of storage at 5.6 °C.
Brodie, BB. "Lack of H1 Gene Expression in Bt Transgenic
Potatoes." [Vol. 77, 394]
During routine evaluation of potato clones and varieties from meristem cultures to confirm their resistance to Globodera
rostochiensis pathotype Ro1, we discovered that cysts developed on Atlantic NewLeaf clone 6 of the Ro1 resistant cultivar Atlantic
that had been transformed with the Bt gene. We obtained a clone of the original nontransformed Atlantic that was used in the transformation
and the transformed Atlantic clones 6, 31, and 36 that were from different transformation events. RFLP analysis of these clones indicated
that all of them possessed the marker for the H1 gene that confers resistance to G. rostochiensis
Ro1. Bioassays in which the plants were subjected to the nematode in pot tests revealed that G. rostochiensis developed freely on
Atlantic NewLeaf clone 6 but not on clones 31 and 36 or on the original nontransformed Atlantic clone. These data indicate that the Bt
transformation process affected the expression of the H1 gene in clone 6 of Atlantic NewLeaf but
not in the other transgenic clones. This finding highlights the importance of evaluating transformed plants for any previously known
resistance traits before they are selected for commercialization.
Brown, CR, D Corsini and R Novy. "Breeding For PVY Immunity: Old Genes, New
Friends."
[Vol. 77, 394]
Potato Virus Y (PVY) is an important pathogen worldwide. Transmitted in a transient fashion by aphids, it is generally considered to be a
difficult control problem in seed programs compared to potato leafroll virus. Presence of inoculum in latently infected varieties, a large
build-up in over the past few years and the ineffectiveness of aphicides have contributed to an emergency level of loss in certified seed and
large depredation in breeding programs in Western States. Curiously, dominant monogenes conditioning immunity to all strains of PVY
have long been available to breeders, yet no important varieties harbor any of these. A program to identify PVY immune breeding parents
harboring the Rysto and Ryadg genes by graft yielded a group of immune clones with diverse attributes. Results from grafting these and
transgenic clones indicate that ELISA values of immune clones are 8% of the susceptible clones, 0.06 versus 0.78. Immune potatoes,
when inoculated, do not buildup virus in foliage, do not pass virus to daughter tubers or provide inoculum to vectors. Full utilization of
immunity genes requires strong economic need, immune parents with high breeding value, and cheap, high throughput methods
to identify immune selections in breeding programs.
Brown, SE, DL Knudson and CA Ishimaru. "Genomic Analysis of the Ring Rot
Bacterium."
[Vol. 77, 394]
Ring rot of potato is caused by the gram-positive bacterium Clavibacter michiganensis subsp sepedonicus (Cms).
We are using technologies developed for genome mapping of animal and plant pathogens to identify potential virulence sequences in Cms.
In previous work, we analyzed the genome structure of Cms strains by contour-clamped homogenous electric field (CHEF) electrophoresis.
A chromosomal band and a single band representing open circular plasmid DNA was present in the CHEF profiles of all strains of Cms.
A band corresponding to plasmid DNA was found in all strains, including those previously identified as plasmid-less. We have verified
the presence of pCS1 by polymerase chain reaction with primers specific for pCS1 sequences and by southern hybridization using pCS1
as a probe. We have also begun sequencing the ends of recombinant clones from a cosmid library of a pathogenic strain of Cms. Our
progress toward identification of potential virulence factors by end sequencing will be presented.
Chang, Dong-Chil, Sung-Yeul Kim, Young-Il Hahm and Kwan-Yong Shin. " Hydroponic Culture
System for the Production of Seed Tubers without Soil." [Vol. 77, 394]
As a part of the National Alpine Agricultural Experiment Station’s (NAAES) alternative for seed tuber production, studies have
been conducted to examine the use of hydroponics for growing potatoes since 1995. The intent would replace the conventional potato
cut tubers or microtubers produced in vitro with the use of minitubers produced in hydroponic culture. These studies involved hydroponic
culture systems, such as deep flow technique (DFT), nutrient film technique (NFT), aeroponic and aero-hydroponic systems as research
tools. At present, the aeroponic system is used in Korea to produce seed tubers because the system provides ample space for tuber growth
and also allows us to harvest them sequentially. However, the main disadvantages of aeroponic systems are pump failure in early stages of
plant growth and small numbers of tubers. We applied aero-hydroponics, a compromise system of aeroponics with DFT, in production of
seed tubers. Growth responses of the plants grown under the aero-hydroponical condition were intermediate of other systems; stem height
was increased in aero-hydroponics compared with that of aeroponics. However, stem height in aero-hydroponics and DFT systems showed
no significant differences. Inhibition of top growth in aeroponics seemed to promote tuber formation. The first indications of tuber formation
were from 26 to 30 days after transplanting. In aero-hydroponics, on the other hand, tuberization in cv. Superior occurred on 29 to 35 days
after planting. In aero-hydroponics, the number of tubers above 1 g was higher as compared to aeroponic system. However, tuber weight per
plant was less in aero-hydroponics. The tuber size distributions produced by each culture system varied with the cultivars. In cv. Atlantic
(mid-late season), the proportion of large tubers (above 10 g) produced was lower in aero-hydroponics than in aeroponics, but that of
minitubers (1-5 g) was higher in aero-hydroponics than in aeroponics. In Superior (early-season), there as no significant difference among
the systems. It can be concluded that aero-hydroponics is suitable for another way of seed production system.
Chang, Dong-Chil, Sung-Yeul Kim and Yong-Boem Lee. "Solution Concentration Effects on Growth
and Mineral Uptake of Hydroponically Grown Potatoes." [Vol. 77, 395]
The influence of solution strengths on growth response and mineral uptake of potatoes (Solanum tuberosum L. cvs.
‘Atlantic’ and ‘Superior’) was studied. The standard strength of nutrient solution contained NO
3- N, P, K, Ca and Mg at the concentrations of 13, 4.2, 7.5 and 3.5 meq/ during stolon growth stage, and 13.5, 4, 8.5 6.5
and 3 meq/ during tuber growth stage, respectively. Three levels of solution strength were used, i.e. standard strength (1.9-2.0 mS
-1), three-fourth strength (1.5 mS-1) and half-strength (1-1.1 mS
-1). During the experiment, solution concentrations were not controlled and changes of mineral
concentration in the nutrient solutions were monitored. NH4+ concentration in half-strength solution
dropped to low levels on 5 to 10 days after treatment, which resulted in increased pH. In stolon growth stage, NO
3- concentration increased in standard strength solution, while decreased in half-strength solution. NO
3- concentration remained as in the initial level in solution of three-fourth strength. In tuber growth stage, NO
3- uptake was inhibited and consequently resulted in increased NO3-
concentrations in all solution strengths. Phosphorus concentration decreased or remained as in the initial level in both stolon and
tuber growth stage. On the other hand, Ca and Mg concentrations increased in all solution strengths. Potassium concentration in the
nutrient solution increased or decreased in the standard or half-strength solutions, respectively. Mineral contents of potato foliages were
determined 90 days after transplanting. In both cultivars, T-N, P and K contents were the highest in the standard strength solution.
However, Ca and Mg contents in plant tissues were constant regardless of solution strengths. Highest growth expressed as fresh
weight of foliages and tubers, and net carbon assimilation (A net) was obtained in the standard strength
solution. Considering the results above, three-fourth strength solution was determined to be optimal for long-term circulation of nutrient
solution.
Coffin, Robert, Rudra Singh, A Dilworth, C Zeng, M Burns, W Hollis, S Moorehead, G Hawkins, D Huestis
and M Singh. "Evaluation of Factors Involved in the Spread of Potato Leafroll Virus in the Potato Variety Russet Burbank in Central
PEI." [Vol. 77, 395]
Potato leaf roll virus (PLRV) has become a problem in some potato growing areas including Prince Edward Island. Some seed fields
in PEI, with negligible virus symptoms during summer inspections, were documented to have high virus infections (15-40%) the following
year. Research was conducted in 1998-99 to determine the time of tuber infection, the effect of proximity between "clean" and
highly infected seed fields and the precision of different post harvest testing techniques. Aphids were collected from yellow pan traps and
tested by reverse transcription polymerase chain reaction (RT-PCR) for PLRV. Virus infections were documented by Florida winter trials,
ELISA and RT- PCR. The virus titer for PLRV in individual plants can vary widely; consequently making composites of tubers or leaves
can result in loss of detection of PLRV when a weak positive is present. Eleven percent of potato aphids, Macrosiphum euphorbiae
(Thomas) and 20 percent of green peach aphids, Myzus persicae (Sulzer) were determined to be "carrying" PLRV virus.
Collection of tubers during the growth of plants revealed 90- 95 % of tubers from symptomatic plants had PLRV where as 30 - 40 % of
tubers from non-symptomatic plants had PLRV. Early generation seed with negligible PLRV, planted directly beside a large field of infected
plants (45% PLRV) became 80% infected with PLRV during one growing season, despite eight applications of aphicides. Ten to twenty
percent of tubers from PLRV infected plants did not test positive for PLRV. Transgenic Russet Burbank clones from NatureMark had very
good "field resistance" to PLRV, and both lab tests and Florida tests confirmed only trace infections when grown under heavy
PLRV pressure.
Coombs, Joseph, David Douches and Kenneth Deahl. "Glycoalkaloid Analysis of Greenhouse
and Field Potato Clones with Host Plant Resistance to Colorado Potato Beetle." [Vol. 77, 395]
Foliar-specific leptines are the most biologically active glycoalkaloid for controlling Colorado potato beetle, Leptinotarsa
decemlineata Say, the leading insect pest of potato (Solanum tuberosum L.) in northern latitudes. Breeding for host plant
resistance in potato foliage against Colorado potato beetle involves insect bioassays using either greenhouse- or field-grown foliage. The
objective of this study was to evaluate glycoalkaloid levels of greenhouse- and field-grown plants with host plant resistance to Colorado
potato beetle. The potato clones evaluated in this study include a high leptine expressing S. chacoense Bitter accession
(USDA8380-1), a glandular trichome germplasm release from Cornell University (NYL235-4), three North Dakota State University (NDSU)
breeding lines with reported resistance to Colorado potato beetle, and Russet Burbank as a susceptible check. Freeze-dried leaf and fresh
tuber samples from greenhouse- and field-grown potato clones were analyzed via HPLC for glycoalkaloid content (solanine, chaconine,
leptines, leptinines, and total glycoalkaloids (TGAs)). The highest foliar TGA levels (48.9 mg/g) and leptine amounts (36.1 mg/g) were
found in USDA8380-1. Breeding lines from NDSU had intermediate amounts of foliar TGAs (14.1-17.4 mg/g), relatively high tuber TGAs
(12.3 - 39.5 mg%), and low levels of leptines (0.9-5.4 mg/g). NYL235-4 had low foliar (6.1 mg/g) and intermediate tuber TGA levels
(13.9 mg%), and no leptines. In general, leaf glycoalkaloid levels of field plants were twice that of greenhouse plants. Consideration of
greenhouse and field effects on glycoalkaloid levels in the leaves are important when conducting Colorado potato beetle bioassays for
host plant resistance.
Corsini, Dennis and Richard Novy. "Leafroll Net Necrosis in Cultivars and Breeding
Selections." [Vol. 77, 396]
Few potato cultivars in commercial production in North America have resistance to leafroll virus (PLRV) infection. However, many are
moderately to highly resistant to the net necrosis symptom in tubers. Important cultivars grown in the northwest and advanced breeding
selections have been tested for leafroll net necrosis in Idaho. Net necrosis was evaluated in tubers from plants exposed to current
season PLRV infection from spreader rows under natural field conditions using a green peach aphid (GPA) strain highly efficient at
transmitting PLRV. Reaction in tubers to PLRV infection was summarized over an eleven-year period. The newly released cultivars
Bannock Russet and Umatilla Russet and a number of advanced breeding selections showed good resistance to LR net necrosis,
similar to Atlantic. Gem Russet, Russet Norkotah, and Ranger Russet were moderately resistant. Russet Burbank and Shepody
were susceptible. CalWhite and Russet Legend were the most susceptible. Cultivars with resistance to net necrosis, including those
genetically transformed for PLRV resistance, can provide protection from the worst effects of current season PLRV infection to individual
commercial growers. However, PLRV management and GPA control programs must take into consideration the threat of viriliferous GPA
spreading from cultivars resistant to net necrosis to the substantial acreage of susceptible Russet Burbank destined for long term storage.
Costanzo, Stefano, BJ Christ and KG Haynes. "Quantitative Late Blight Resistance in an
F1 Diploid Solanum phureja X S. stenotomum Population." [Vol. 77, 396]
Late blight, caused by Phytophthora infestans, is the most important fungal disease of potato worldwide. Since this fungus is able
to rapidly overcome major race-specific resistance genes, breeding for more durable resistance has become a high priority. Quantitative
resistance of foliage to late blight was evaluated in a diploid potato F1 population grown in field trials in
PA during 1999. A cross between a highly resistant and a highly susceptible diploid Solanum phureja X S. stenotomum clone
resulted in 240 F1 progeny. The two parents and three control cv. (Atlantic, Kennebec and Katahdin) were
included. The experimental design was a randomized complete block with two replications. A mixture of three isolates of P. infestans,
clonal lineage US-8, was used to inoculate spreader rows. Percent defoliation was estimated visually in each plot four times during the
season and area under disease progress curve (AUDPC) was calculated. AUDPC ranged from 67 to 1000, with an overall mean of 610 and
a standard deviation of 205. The observed distribution was skewed towards higher AUDPC values. There were significant differences
between replications and among clones. The nature of the distribution suggests that resistance to late blight in this diploid population is
quantitative. This segregating population is now being analyzed for linkage between restriction fragment length polymorphism (RFLP)
markers and quantitative trait loci (QTLs) affecting resistance to late blight.
Culley, David, Ching-Pa Yang, Bill Dean and Charles Brown. "Characterization of the Polyphenol
Oxidase Gene Family from the Low Browning Solanum Species, S. hjertingii." [Vol. 77, 395]
In an attempt to better understand the mechanism responsible for the low browning trait observed in the tubers of the wild tetraploid
species Solanum hjertingii we have cloned and characterized several members of the polyphenol oxidase gene family from this
species. Using PCR primers designed to amplify a 1.2 kb region of a known S. tuberosum PPO gene sequence (POT32), a series
of PPO related sequences were amplified from S. hjertingii DNA and cloned. The sequences of these clones represented 5
distinct genomic sequences showing varying degrees of homology with known S. tuberosum PPO sequences. One clone in particular
(HG9) was interesting because it represented a 0.6 kb PCR band present in all S. hjertingii accessions (and crosses with this species)
that expressed the low browning trait. This clone was sequenced and shown to represent a truncated 0.6 kb PPO sequence in which the
two copper binding regions required for activity had been deleted. From the sequences of the genomic PCR clones, primers were designed
to clone the flanking regions from these loci using inverse PCR. Several clones have been isolated using this strategy, including one that
contains the region upstream of the truncated HG9 PPO gene. Comparisons of the S. hjertingii PPO genes with the S.
tuberosum genes will be presented, along with data on the transcription of these genes.
Culley, David, Elzbieta Skrzeczkowska, Bill Dean, and Charles Brown. "Progress Towards
Introgression of Blackspot Bruise Resistance from Solanum hjertingii into Cultivated Potato Varieties."
[Vol. 77, 396]
Blackspot bruise continues to be a serious quality problem, threatening profitability to growers. One approach to reducing this problem
is to utilize the genetic factors responsible for the low browning observed in some wild Solanum species. We will describe the results from
our attempts to introgress the low browning trait from the wild species, S. hjertingii, into cultivated S. tuberosum. To
introgress S. hjertingii, an intermediate bridging hybrid was utilized. The progeny of the initial cross between S. hjertingii
and a high browning cultivated diploid showed very low tuber browning, indicating a high degree of dominance. The triploid progeny from
this cross were subjected to in vitro chromosome doubling and the resulting hexaploid lines were crossed with cultivated S. tuberosum.
Tubers from the resulting pentaploid seed progeny were evaluated for browning and PPO activity. Again, we observed almost complete
dominance of the low browning trait. However, in contrast to previous reports, a kinetic PPO assay revealed a range of PPO activities, with
low melanin accumulation occurring even in the presence of high PPO activity. The progress we observed toward decreased browning in
these crosses suggests that this approach has great potential for improving blackspot bruise resistance in cultivated potato.
Davis, JR, OC Huisman and AT Schneider. "Comparative Survival of Verticillium dahliae on Sixteen
Rotation Crops" [Vol. 77, 397]
During the 3 years of this investigation, all rotation crops were less susceptible to Verticillium dahliae (Vd) colonization than
Russet Burbank potato. Nevertheless, all were colonized to some degree. The least colonization occurred in sudangrass (HS33), field
corn (NK), alfalfa (Pioneer 5472), sugarbeet (HMR2), and turnip. Among rotation crops compared, oat (Cayuse) was among the most
susceptible and provided a consistent source of inoculum ranging from 103-10
4 cfu Vd g-1 of plant tissue. In both 1996 and 1998, Vd recovery
from buckwheat (Targo) did not differ from oat recovery, but in March of 1999, Vd recovery from buckwheat was 3-fold higher than oat.
Oat was more heavily colonized than either sugarbeet or tomato. When compared with other monocots, oat was more heavily colonized
with Vd than either wheat (Penawawa), barley (Russell), sudangrass, or field corn. Among legumes, milkvetch (Cicer) and oats did not
differ in Vd susceptibility but were consistently more susceptible than alfalfa (Pioneer 5472). Differences between either clover (Ladino)
or Austrian winter pea with oat were not consistent. Among Brassica crops, radish (Forage) was similarly colonized to oats while canola
(Weston), rape (Dwarf Essex), and turnip were less colonized. Results provide evidence for sources of Vd survival with rotation crops.
Deahl, KL and RW Goth. "A Detached-Leaf Method to Evaluate Oospore Pathogenicity in
Potato." [Vol. 77, 397]
The pathogenicity of oospores Phytophthora infestans, the causal organism of late blight, was determined on detached leaves of
potato. We excised primary leaves from the third to the sixth node of sterile healthy plants and inserted their petioles into 14 mm x 100 mm
floral aqua tubes containing 9 ml of sterilized distilled water. Leaves in the aqua tubes were placed, abaxial sides down, on galvanized
metal hardware cloth (12.5 x 12.5 mm mesh) and positioned 2.5 cm above distilled water (2.5 cm depth) in 31 cm x 17 cm x 8 cm clear plastic
boxes with tight fitting lids. The plastic containers were kept in growth chambers at 16°C and 16 hour photo period of mixed fluorescent
and incandescent light. Single germinating oospores were placed in the center of the terminal leaflet in a droplet of water on each test leaf.
Eight days after an inoculation, characteristic late blight symptoms developed on the inoculated leaflets. This detached-leaf method was used
to demonstrate the abilities of single oospore offspring to infect, colonize and sporulate on potato leaves. Although the importance of
sexual recombination in establishing and maintaining diversity is unclear and presumptive, this technique could be utilized in efforts to
delineate the precise role of oospores in the disease and life cycles of this organism.
Delgado, Efren. "Qualitative Aspects of Potato Tubers Determined by Water Availability During
Growth." [Vol. 77, 398]
The effect of water stress on the quality of potato tubers with different darkening tendency was analyzed before and after storage.
Tuber yield, tuber size ratio, starch content, protein content, potential of darkening, polyphenol oxidize activity and storage capacity were all
factors affected by water stress. A positive correlation was found between the tuber's oxidative potential and its content of chlorogenic
acid, citric acid and free phenylalanine, while the correlation was found to be negative vis-à-vis ascorbic acid and potassium content. There
was no direct relation between total and free tyrosine, polyphenol oxidize activity and the tuber's oxidative potential. The highest polyphenol
oxidize activity was found in soluble proteins. Polyphenol oxidase activity was not affected by water stress but decreased drastically
during storage. Oxidative potential, however, was found to increase. The ratio between free and protein-bound tyrosine did not appear to be
influenced by the potassium contained in the tuber. Water stress during growth affected the quality of potato tubers, such as oxidative
potential and storage capacity.
del Rio, Alfonso H and John B Bamberg. "Impact of Genebank's First Seed Increase on the Genetic
Differentiation of Collected Wild Solanum (Potato) Species." [Vol. 77, 398]
Ex situ conservation of wild potato germplasm provides a basic resource for potato crop improvement. RAPD markers can be used to
characterize the status and dynamics of genetic diversity in such populations, providing insights into the best management practices for
preserving it. Previous work at the US Potato Genebank indicated that seed increase generations within populations were very similar.
However, when in situ populations were re-collected from the wild and compared to the corresponding genebank-conserved samples,
large differences were detected. This work investigates one possible cause of these differences: A large genetic change in the sample
when it undergoes "domestication" by a forced sexual seed increase and subsequent adaptation to cultivation in the genebank.
Thus, RAPD markers were used to compare clonal samples from the wild with their seedling progeny derived from a typical genebank
sexual seed increase. Such comparisons showed that incorporation of germplasm into the genebank incurs negligible genetic change,
and does not explain the large differences observed between samples conserved in the genebank for many years and re-collections from
their corresponding sites of origin in the wild.
Dong, Fenggao, J Mitchell McGrath, Ahmet L Tek, Geraldine T Haberlach, John P Helgeson and Jiming Jiang.
"Development and Characterization of Solanum brevidens Chromosome Additions/Substitutions in Potato."
[Vol. 77, 398]
Backcross progenies derived from a somatic hybrid between potato and a wild species Solanum brevidens (2n=2x=24) were
analyzed using both molecular and cytogenetic methods. Ten plants were isolated as putative potato-S. brevidens chromosome
addition/substitution lines based on presence of S. brevidens-specific RAPD markers. The S. brevidens chromosome(s)
were identified by genomic in situ hybridization analysis. The identities of the S. brevidens chromosomes were analyzed by
fluorescence in situ hybridization using chromosome-specific cytogenetic DNA makers. Using this comprehensive approach, we isolated
seven potato-S. brevidens monosomic addition lines (chromosomes 1, 3, 4, 5, 8, 9 and 10) and one potato-S. brevidens
monosomic substitution line (chromosome 6). The remaining four chromosomes of S. brevidens (chromosomes 2, 7, 11, and 12)
were recovered in two other plants. We demonstrated that individual chromosomes from a wild Solanum species can be transferred
into potato using a backcrossing approach. Resistance genes against a number of potato pathogens can be localized on individual S.
brevidens chromosomes using the isolated addition/substitution lines.
Fisher, David G. "Evidence of Horizontal Resistance in Solanum tuberosum to Colorado Potato Beetle
(Leptinotarsa decemlineata Say)." [Vol. 77, 398]
In spite of older literature that records low levels of resistance to the Colorado potato beetle (CPB) in some varieties of cultivated potatoes,
no attempt has been made to develop horizontal resistance (HR) to this serious pest. In view of the well-established durability of HR, the
purpose of this research was to assess the potential for developing such resistance, beginning with potato varieties that grow well in Iowa
and using a leaflet bioassay to screen feeding behavior. Individual leaflets of field-grown plants were inoculated with 10 hatching CPB eggs
in petri dishes (4-7 replicates) or while still attached to the plant (3 replicates). Two or three days after inoculation, resistance to feeding was
determined using the formula C = AD N-1, where C = mg leaf tissue consumed per larva, A = leaf area
consumed (leaflet-1), D = leaf density, or mg leaf tissue cm-2, and N = the number of feeding larvae.
In the F2 generation, C for the six most resistant genotypes combined was significantly lower than
the resistant varieties NYL235-4 and ND2858-1 as well as the susceptible varieties Yukon Gold and Red Norland. Individually, C for the
resistant F2 genotypes was 17-54% lower than NYL235-4 and 9-38% lower than ND2858-1. The
three-day field exposure of attached leaflets to CPB larvae resulted in approximately the same pattern of feeding as the detached leaflet
bioassays. The achievement of this degree of resistance after only two rounds of breeding while using relatively small populations suggests
that HR to CPB can be developed from varieties of Solanum tuberosum that lack initial high levels of resistance to this pest.
Frazier, MJ, GE Kleinkopf and TL Brandt. "Spearmint Oil and Peppermint Oil Used as Alternative
Sprout Suppressants." [Vol. 77, 399]
Spearmint and peppermint oils are being investigated as alternatives to isopropyl-M- chlorocarbamate (CIPC) for sprout suppression
in long term potato storage. Carvone, the main component of spearmint oil, has been used successfully for sprout suppression in Europe.
Menthol is the major component of peppermint oil and appears to work by physically burning the sensitive meristimatic sprout tissue.
Methods of application, ventilation, and rate of application were tested. Sprouting, sugar concentrations, and USDA fry colors were compared,
in Russet Burbank, over a nine-month storage period. A taste panel evaluated samples after 8 months in storage. A cost analysis was
prepared.
Mint oils must be repeatedly applied for long-term sprout control due to the volatility of the compounds but some applications provided
successful sprout suppression for 8-9 months after harvest. Cold aerosol applications were less effective than wick applications, which
suppressed sprouting for approximately 3 months longer than the aerosol treatments. Vented and recirculated storage methods were
also evaluated. Generally, mint oils did not impact reducing sugars or USDA fry color. Some members of the taste panel found the flavor of
potatoes treated with spearmint oil objectionable. Peppermint treated potatoes were not rated as tasting differently from CIPC treated potatoes.
Spearmint and peppermint oil may be used successfully for sprout suppression on potatoes in short or long term storage but cost
($.03-.83/CTW) may be significantly higher than CIPC treatment.
Geary, Brad, PB Hamm, DA Johnson, SR James and KA Rykbost. "Effects of Fungicides and
Location on Development of Silver Scurf." [Vol. 77, 399]
Silver scurf of potato, caused by Helminthosporium solani, is a disfiguring disease of the tuber periderm that reduces
marketability, particularly in fresh-marketed potatoes. This study was conducted to determine the efficacy of seed treatments to control
silver scurf in progeny tubers at several geographically isolated and environmentally different potato production areas. Fungicide treatments
were applied to certified Russet Norkotah seed from the same seed lot previously identified to have a high incidence and severity of infection.
Plots were established at four locations: near Redmond, Klamath Falls, and Hermiston OR and Othello WA in 1998 and 1999. Disease
incidence and severity differed significantly among the four locations. Seed tubers treated with Maxim (8 oz / cwt) + Blocker (26.5 oz / 1000 ft
row in furrow); Quadris (8 oz / cwt); Maxim (12 oz / cwt); Tops MZ (12 oz / cwt); and Tops MZ (16 oz / cwt) had significantly less disease than the
other treatments regardless of year or location. Differences in seed treatments suggest fungicides at planting reduced disease severity on
progeny tubers by reducing the number or production of viable spores coming from the seed tubers. Differences in disease levels at the four
locations also suggest that geographical/environmental conditions may influence silver scurf severity.
Gundersen, B, D Inglis; L Porter, J Miller, D Johnson and C Brown. "Comprehensive Laboratory
and Field Assessment of Resistance to Phytophthora infestans Derived from Solanum hougasii in a Segregating Breeding
Population." [Vol. 77, 399]
Significant losses to the U.S. potato industry due to late blight have placed a new demand on potato breeding programs to develop
cultivars with durable resistance. A mapping population was established with 1) an accession of S. hougasii from Mexico and 2)
corky ring spot resistant parental lines, and tested against US-8 and US-11 genotypes of P. infestans. Foliar disease reactions of 75
progeny were compared in natural field epidemics in Mount Vernon. Area under disease progress curve (AUDPC) values for control plants
(cv Russet Burbank) were 4909 and 2538, but values for progeny ranged from 234 to 5650 and 349 to 2967, during 1998 and 1999,
respectively. Moreover, 10 and 12 percent (pct) of the progeny were rated as highly resistant, and 40 and 39 pct were rated as highly
susceptible, over the two respective years. Tuber reactions in laboratory assays in Pullman ranged from 0 to 68 pct internal blight; the
control (cv Ranger Russet) had 72 pct internal blight. Foliar and tuber resistance were not highly correlated (r=0.52, 0.27) either year when
analyzed by population, although some individual lines exhibited resistance in both the foliage and tubers. Foliar resistance in the field was
characterized by leaf chlorosis, limited lesion expansion, and few sporangia per lesion.
Gupta, Sanjay, Joe Sowokinos and Irene Shea. "Isolation and Characterization of Cold Sweetening
Resistant Isozymes of UGP-GLC Pyrophosphorylase (UGPase) from Potato (cv. Snowden)." [Vol. 77, 400]
Genetic analysis has indicated that three key loci are involved in the process of cold-sweetening in potato tubers (Thill and Peloquin,
1994, Am. Potato J. 71:629-646). However, little agreement exists as to the identity of these genes, how they are regulated, or what their
relative contribution is to the overall process of sweetening. It is essential that these genes be identified and sequenced and that the
function and in vivo regulation of their gene products be clarified. UGPase is an important enzyme in the sweetening pathway in that it
catalyzes the first committed step of the process which leads to the formation of reducing sugars. Recent studies have suggested that
the complement of UGPase isozymes in potatoes may serve as an effective tool to screen new hybrid potato-progeny for cold-sweetening
resistance. Cold-sensitive cultivars contain isozymes UGP1, UGP2, and UGP3, with UGP3 being the most abundant. UGP3 has previously
been purified from the cultivar Norchip (Sowokinos et al., 1993, Plant Physiol 101:1073-1080). Cold-sweetening resistant potatoes
demonstrate two additional isozymes of UGPase designated UGP4 and UGP5. In this study the UGPase isozymes UGP4 and UGP5 were
purified to homogeneity. A subunit mass of 53 kD was obtained using SDS-PAGE. Their physical and catalytic properties will be discussed
in relation to their role in regulating cold-induced sweetening in potatoes.
Hafez, SL and P Sundararaj. "Application and Placement of Nematicides in the Management of
Stubby Root Nematode and Corky Ringspot Disease of Potato." [Vol. 77, 400]
Two separate field experiments were conducted during 1998-1999 to study the efficacy of nematicides for control of stubby root
nematode and corky ringspot disease of potato in eastern Idaho. In the first experiment Temik 15G (22.44 kg/ha) was applied at planting
as in furrow at planting (IFAP), modified in furrow at planting (MIFAP), or in front of shoe at planting (FOSAP) and an untreated check plot
was included. Stubby root nematode population among treatments ranged from 80 to 162 per 500 cc soil at 0-30 cm depth and from 296 to
796 per 500 cc soil at 30-60 cm depth. Application of Temik significantly increased total and marketable yield of potato compared to the untreated
control. A significant reduction in potato yield (4%) due to the corky ringspot disease was observed in the untreated control plots as
compared to treated plots. In the second experiment Temik was applied as above and Admire 2F (1.4 1/ha) was applied as an IFAP
treatment, Vydate L (7 1/ha) was applied twice as a foliar spray when the potato plants were 8-10" tall (29 Jun) and again at row closure
(20 Jul) to plots previously treated with Temik 15G (22.44 kg/ha, IFAP). Yield loss due to stubby root nematode and corky ringspot incidence
ranged from 6 to 55%, and resulted in significant differences in total and marketable yields adjusted for corky ringspot disease. Temik
applied IFAP, MIFAP or IFAP in combination with foliar applications of Vydate resulted in the lowest incidence of corky ringspot disease and
had the highest total and marketable yields. Temik applied FOSAP or Admire 2F applied IFAP tended to be less effective than other
placements.
Hahm, Young-Il, Kook-Hyung Kim, Hyo-Won Seo and Hyo-Won Jung. "Characterization of Tobacco
Mosaic Tobamovirus Isolated From Potato in Korea." [Vol. 77, 400]
Tobacco mosaic tobamovirus (TMV-TK) was isolated from infected potato (Solanum tuberosum cv. Superior) showing mosaic
symptoms and necrotic spots on leaves in the Kangwon area, Korea. EM observation of the purified virus particles showed rod shape about
300 in length. The coat protein of the virus had a molecular weight of 18 21 .5 kd in SDS-PAGE analysis, and the viral RNA was
approximately 6.4 kb in size in denatured agarose gel electrophoresis. With a polyclonal antiserum produced against purified TMV-TK
particles, TMV-TK was rarely found in cultivated potatoes in Kangwon area. Both Chenopodium amaranticolor and C. quinoa
developed necrotic local lesions 7 days after inoculation, and systemic veinal chlorosis with distortion was evident on new leaves 2 weeks
after inoculation but S. tuberosum cv. Superior showed necrotic spots on inoculated leaves. Data from host range studies suggest
that TMV-TK behaves similarly to other tobamoviruses in the TMV subgroup such as tomato mosaic virus (ToMV). TMV-specific cDNA clones
were obtained by RT-PCR cloning and the resulting clones were sequenced. Sequence comparison using the coat protein amino acid
sequence showed that TMV-TK shares 92-95% identity with those sequences of TMV subgroup. Based on serological reactions in direct
ELISA with polyclonal antibodies, host range studies, and the sequence analyses, TMV-TK is considered a member of the TMV subgroup.
Hale, Anna L, J Creighton Miller, Jr, Jeannie P Miller and R Daniel Lineberger. "The PAA Web Site
– Goodbye Texas, Hello Maine." [Vol. 77, 400]
The PAA web site was developed at Texas A&M University and went online in November of 1997. Initially, the site consisted of a
directory of current officers and section chairs, the North American Potato Variety Handbook, a membership application, and historical
information on meeting sites, officers, and honorary life members. Information on meeting site, program, and registration, as well as
selected section pages were soon added. Recent additions include new section pages for entomology, utilization and marketing,
extension, and pathology. In preparation for transfer of the site to headquarters in Orono, ME, as recommended by the Website Advisory
Committee ,updates were made for officers, section chairs, committees, past officers, past and future meetings, and new e-mail addresses.
The site was successfully transferred at the beginning of March, and Lori Wing assumed all responsibility for the site at this time. Between
November 1997 and October 1998, there were 6,815 html pages requested, but due to a program change, this information is not available
from November 1998 to February 2000. Since the creation of the site in mid November of 1997 to the transfer of the site in February of 2000,
a total of 29,981 files were requested from the PAA site. These included html files as well as jpegs. The number of requested files
increased from 721 in December 1997 to 1651 in February 2000. The site has been an enormously successful medium for the
dissemination of PAA and general potato related information to members and potential members.
Hamlen, RA, JL Genet, C Shepherd and R Geddens. "Famoxateâ: A New and Unique Fungicide
for Use in the Management of Early and Late Blight of Potato." [Vol. 77, 401]
Famoxateâ, a novel broad-spectrum oxazolidinedione (non-stobilurin) fungicide discovered and patented by DuPont for use in premixture
with cymoxanil, offers unique control of Phytophthora infestans and Alternaria solani. Key premixture attributes are
complimentary and multi mode- and site-of-action, favorable toxicology and environmental profiles, and high grower acceptance via a dry
flowable formulation. KP-481 (Tanosâ), a premixture of Famoxateâ, a mitochondrial cytochrome bc1
complex inhibitor, and cymoxanil, an inducer of a host-defense response in potato, includes the sporangia and zoospore killing action
of Famoxateâ coupled with the penetrant, systemic, curative, and antisporulant activity of cymoxanil. A. solani strains exhibiting
reduced sensitivity to chlorothalonil are well controlled by Famoxateâ. Laboratory to field assessments demonstrate the value of this single
product with either individual or duel infections of early and/or late blight. Global sensitivity profiles and selection studies with Famoxateâ
indicate low risk to cause rapid shifts in P. infestans sensitivity, while activity profiles with >I>A. solani show a uniformly sensitive
population to Famoxateâ. Cymoxanil has been used worldwide for more that 20 years in potatoes without resistance occurrence.
Famoxateâ in premixture with cymoxanil and used in preventive disease management programs, including different mode- and
site-of-action fungicides, offers a sound resistance management tool and effective control of these potentially devastating diseases of
potatoes.
Hane, Dan C and Philip B Hamm. "Efficacy of Vapam Rates on Soil-Borne Fungi and Yield of Four
Potato Cultivars." [Vol. 77, 401]
Test plots were treated with either 514, 257, or 0 liters per hectare of Vapam (32% sodium methyldithiocarbamate). Treatments were
spring applied through a center pivot system. Trials were conducted in 1996 and 1998 on sandy soils in the Columbia Basin of Oregon.
Soil populations for Pythium sp., Fusarium sp., and Verticillium dahliae were determined prior to fumigation, again
after fumigation (before planting), and at harvest. Russet Norkotah, Shepody, Ranger Russet, and Russet Burbank were evaluated for
yield characteristics under each treatment level. Soil pathogen levels generally declined with applications of Vapam, but recovered as the
season progressed. Yields were increased in all varieties with the application of Vapam, particularly at the highest rate. The use of Vapam
is beneficial in the Columbia Basin, even for short season cultivars (Russet Norkotah, Shepody) and Verticillium wilt resistant
cultivars (Ranger Russet).
Hayes, Ryan, J and CA Thill. "Early Generation Selection for Cold Chipping in Diverse Potato
Progenies." [Vol. 77, 401]
Chip color is market limiting for chipping cultivars, without acceptable color other traits have reduced value. Cold temperature storage
reduces microbial spoilage and chemical use on potatoes. Early selection for cold chipping can reduce development time, while the use of
diverse parents may give gain for other traits, when selecting 1st for chipping. Our objectives were to determine 1) when variation for cold
chipping could be identified, and 2) if parental diversity influences cold chipping frequencies. Progeny from 4x-4x crosses were grouped by
matings based on assumed genetic diversity, Tw- within and, Tb- between breeding programs, and Td- diverse using wild species. The
number of families in each group was Tw-45, Tb-63, and Td-67, totaling 3312 progeny. Chips were made from greenhouse seedling
tubers (ST) after 6-mo. and from field single-hill tubers (SH) after 3-mo. storage, at 4C. Chips were scored 1-10, < 4 being acceptable
color. Mating group color means were significantly different Tw/ Tb/ Td- 7.41/ 8.19/ 7.68 (ST) and 7.60/ 8.19/ 7.94 (SH). Progeny chipping <
4 totaled 203/32 (ST/SH). Families performing best were in the Tw group, having the lowest means and highest percent of progeny <
4. Regression of SH family means on ST means indicated that ST family performance was only moderately predictive of SH family
performance; r2=0.357. Means from ST and SH were significantly different and the SH test had a
reduced color variance and frequency of progeny < 4. Cold chipping was found in ST populations but selection may result in false positives.
Repeatability over years and applying to other potato market-types continues.
Haynes, KG "Two Cycles of Recurrent Selection for Specific Gravity in Diploid Potatoes: Effect on
Inheritance of Yield and Specific Gravity." [Vol. 77, 402]
All of the high specific gravity cultivars in the U.S. are very closely related, which increases their genetic vulnerability and results in
inbreeding as efforts are made to improve specific gravity. The use of diploid Solanum species in breeding may solve these problems.
The purposes of this study were to estimate narrow-sense heritability and phenotypic variation for yield and specific gravity in
random-mating diploid hybrid populations of S. phureja x S. stenotomum (PHU-STN) during two cycles of recurrent selection
for specific gravity. Four clones from each of 72 maternal half-sib families were evaluated for yield and specific gravity in two selection cycles
in replicated field tests in 1990-1991 (cycle 1) and 1995-1996 (cycle 2). Narrow-sense heritability for specific gravity was estimated as
0.37 + 0.25 (cycle 1) and 0.43 + 0.27 (cycle 2), with a 27% decrease in phenotypic variance between cycles. Narrow-sense heritability for
yield was estimated as 0.60 + 0.26 (cycle 1) and 0.06 + 0.24 (cycle 2), with a 73% decrease in phenotypic variance between cycles. These
results indicate that additional breeding efforts in this PHU-STN population could improve specific gravity. However, the amount of variation
for yield is decreasing rapidly, and may indicate that the yield potential of this population is approaching its limit.
Haynes, KG, DS Douches, CA Thill, G Secor, WE Fry, BJ Christ and RW Goth. "Foliar
Resistance to Late Blight in Potato Clones Evaluated in National Trials in 1999." [Vol. 77, 402]
With the emergence of new and more aggressive strains of Phytophthora infestans and the release of new potato cultivars, an
evaluation of potato clones for resistance to late blight is necessary. Thirty-nine potato clones (23 cultivars, 16 selections) were
evaluated in 1999 for late blight resistance at six U.S. locations, along with eight late blight differentials. Among the 23 cultivars evaluated,
8 have been released within the past two years. Percent infected foliage was recorded at approximately weekly intervals following the onset
of disease at each location. Clones were ranked for mean AUDPC within locations and analyzed for phenotypic stability using
nonparametric statistics. There were significant genotype x environment interactions on the rankings of these clones across locations.
The most late blight resistant clones were AWN86514-2, B0767-2, and A90586-11. AUDPC was minimal in the late blight differentials
LBR8 and LBR9 across all locations. As a group, the mean AUDPC of the eight newest cultivars was 880, compared to 925 for the nine
most widely grown cultivars indicating some small gains are being made in improving late blight resistance in new cultivars.
Holm, Amy L, Viviana V Rivera, Gary A Secor and Neil C Gudmestad. "Sensitivity to Potato Early
Blight, Alternaria Sp., to Protectant Fungicides." [Vol. 77, 403]
Sensitivity to chlorothalonil, triphenyl tin hydroxide (TPTH), mancozeb, and azoxystrobin was determined for Alternaria solani
and Alternaria alternata isolates collected from a wide geographic area in 1998 and 1999. Specifically, the relative sensitivity
of A. solani field populations from several commercial fields to the protectant fungicides were evaluated in order to determine if
sensitivity to protectant fungicides changes during the growing season. Sensitivity to the protectant fungicides was determined by utilizing
the spore germination and radial growth assay methods. The fungicide concentration that inhibited growth by 50 percent (EC
50) was estimated for each isolate. In several locations, regular exposure of A. solani populations to
chlorothalonil resulted in a wider range of sensitivity among isolates and temporary shifts in sensitivity existed within most field populations
during the course of the growing season. However, because there were few TPTH and mancozeb applications used in these locations,
there was less variance for TPTH and mancozeb than for chlorothalonil. In addition, sensitivity of A. solani field populations to TPTH
and mancozeb did not change, rather the EC50 values remained the same throughout the growing
season. All of the A. solani isolates tested were sensitive to azoxystrobin with a mean EC50
value of 0.04 micrograms/ml; however, the A. alternata isolates were less sensitive to azoxystrobin (mean EC
50 value of 0.61 micrograms/ml) than the A. solani isolates. A. alternata was also less sensitive to
mancozeb (mean EC50 value of 2.5 micrograms/ml) than A. solani.
Hoover, Ronald, Peter Karnezos and Warren Pinkston. "Response of Potato to Crop-Set
TM Bio-Stimulant." [Vol. 77, 403]
Crop-Set is a liquid product containing natural ingredients and micronutrients. It has been shown to improve yield and quality of the
marketable fraction of many fruits and vegetables. A single foliar application of 8 oz/acre is recommended for potatoes. Treating potatoes
soon after stolons begin to swell (0 to 0.5" diameter tuber) results in enhanced tuber numbers and yield of all tuber sizes. Delaying
the application until the onset of rapid tuber fill (1 to 1.5" diameter tuber) enhances tuber bulking and uniformity, and reduces the
number of small tubers. Initial tests conducted in the northern US and internationally report increases of 5 to 15% for tuber number and
yield, with some approaching 25% during difficult growing conditions. Crop-Set was evaluated under production conditions in north Florida
during the winter growing seasons of 1998 and 1999. Growing conditions were very favorable and crop performance was high. When
applied early to Red La Soda, La Rouge, and Sebago, Crop-Set improved total tuber numbers by 4.7% and increased the untreated yield
of 418 cwt/ac by 16 cwt/ac (p=0.10) in 1999. Crop-Set was applied to improve bulking (approx. 1 to 1.5" diameter tuber) of Atlantic,
Snowden, and Frito 1625. Compared to untreated potatoes, Crop-Set increased the yield of market-sized (>1.875") tubers
during 1998 and 1999 by 20 cwt/ac (p=0.01) and 19 cwt/ac (p=0.10), respectively. Although growing conditions and tuber yields were very
good, the response of potato to Crop-Set was very consistent.
Huffman Wohleb, Carrie and Robert E Thornton. "Effects of Irrigation and Nitrogen Management
on Five Potato Cultivars." [Vol. 77, 403]
Understanding the individual management needs of potato (Solanum tuberosum L.) cultivars is necessary to realize their yield
and quality potential. This research was undertaken to compare patterns of growth and development of five main-season potato cultivars
and to test their response to preplant nitrogen fertility and inseason irrigation management. Field trials were conducted in 1998 and 1999
to compare two standard cultivars; Russet Burbank and Ranger Russet, two recently released cultivars; Umatilla Russet and Bannock Russet,
and NatureMark's genetically modified NewLeaf Russet Burbank. Plants were subjected to two levels of irrigation; a standard level of
irrigation and a drier deficit treatment maintained with longer intervals between water application. Two preplant nitrogen fertility levels were
created each season; 225 and 330kg N ha-1 in 1998,112 and 225kg N ha-1
in 1999. Plant growth and tuber development was evaluated at several dates during the growing season. Final harvest occurred 150 days
after the planting date. Results from these studies indicate cultivar differences in plant emergence, vine growth rate and time of vine senescence,
petiole nitrate concentration and seasonal trend, timing of tuber initiation, tuber bulking rate with time, tuber grade, and tuber specific gravity.
The level of preplant nitrogen supplied influenced cultivars differently, especially in regards to vine growth patterns and early tuber
development. Deficit irrigation reduced tuber quality in all five cultivars, but the degree of reduced quality depended on the cultivar grown.
These results demonstrate the need to develop cultivar specific management practices.
Hyde, GM and AL Baritelle. "Tuber Conditioning to Minimize Impact Bruising."
[Vol. 77, 403]
This presentation discusses a new model for predicting bruise thresholds in potato tubers based on tuber characteristics and
conditioning. Tuber mass, radius of curvature, and tissue dynamic failure stress and elasticity are model variables. The paper reports
effects of temperature and turgor conditioning, and strain rate on failure stress and elasticity. The model validation predicted bruise
threshold to within 2 mm of experimental values for potato tubers, and within 1 mm for apples.
Ingham, Russell E and Philip B Hamm. "Water-Run and Shanked Applications of Metham
Sodium for Control of Tuber Infection by Meloidogyne chitwoodi and Corky Ringspot in the Columbia Basin of Oregon."
[Vol. 77, 403]
Several trials in the early 1990's demonstrated that metham sodium applied through chemigation (water-run) at rates up to 74 gpa
(42% a.i. formulation) could not control tuber infection from Columbia root-knot nematode (Meloidogyne chitwoodi) or corky
ringspot (CRS), caused by tobacco rattle virus, vectored by stubby-root nematodes (Paratrichodorus allius). In 1996, metham sodium
at 38 gpa shanked-in at 16 in. (SHMS) reduced the percent of tubers with CRS to 2% compared to 26% and 33% in untreated and water-run
metham sodium (WRMS) at 38 gpa treatments, respectively. Similarly, tubers culled from M. chitwoodi were 32%, 22% and 1% in
untreated, WRMS and SHMS plots, respectively. In 1999, WRMS and shanking-in metham sodium at 6, 12 and 18 in. at 38 gpa, reduced
the percent of tubers with CRS to 2% and 8%, respectively, compared to 59% in the untreated check. However, root-knot nematode infection
was not reduced by either treatment averaging 22%, 26% and 20% culled tubers in the untreated, WRMS and SHMS treatments respectively.
Increasing the rate of SHMS to 50 gpa controlled both CRS (3%) and root-knot culled tubers (1%).
Jansky, Shelley and Doug Rouse. "Early Generation Selection for Verticillium Wilt
Resistance." [Vol. 77, 404]
Host plant resistance offers a promising method for the control of Verticillium wilt. It is important for potato breeders to determine
the most efficient and effective strategies for incorporation of resistance into their programs. This study was carried out to determine
whether resistance could be detected in early generations of a breeding program. Seedlings from crosses between clones with varying
levels of resistance were planted in a Verticillium dahliae screening plot. They were scored for vine maturity, Verticillium wilt
symptoms, and levels of V. dahliae propagules in their stems. They were planted in years two and three in two- and four-hill plots,
respectively, with two replications per plot. In each year, there was a significant negative correlation between vine maturity and
Verticillium wilt resistance. However, the correlation coefficients were generally not numerically high, so not all clones were
expressing immature plant resistance. Verticillium wilt symptoms did not always correlate with levels of V. dahliae in stems. In
addition, resistance based on symptoms or propagules in stems did not always correlate across years. Selection based on small plots may
not be sufficient to detect Verticillium wilt resistance.
Jensen, Heather M and Joseph F Guenthner. "Economics of Net Necrosis in the Frozen Potato
Processing Industry." [Vol. 77, 404]
Potato Leaf Roll Virus (PLRV) is a serious disease in the potato industry. Tuber discoloration or Net Necrosis can be a result of PLRV
infection. Infected tubers are unacceptable for frozen fry processing. Russet Burbank, the most popular processing variety, is highly
susceptible to PLRV. NatureMark, a subsidiary of Monsanto, has developed a genetically altered Russet Burbank (NewLeaf Plus) that is
resistant to PLRV. This study evaluates the cost of Net Necrosis to frozen fry processors by examining the infection rate of potatoes used by
processors and the factors that contribute to the amount of disease. Net Necrosis models were developed for Washington's Columbia Basin.
Variables analyzed were location, aphid pressure, and seed PLRV infection. The cost of Net Necrosis was determined through interviewing
individuals involved in the frozen fry processing industry. This information provides processors with a cost analysis of Net Necrosis and
helps them predict potential costs for the next year during the current growing season. This study also provides NatureMark with an estimated
value of their NewLeaf Plus variety in the processing industry.
Jones, Richard W. "Analysis of Prosystemin in Potato." [Vol. 77, 404]
Prosystemin is a small protein (20 kDa) that is produced in response to insect feeding or wounding. The protein is processed, releasing
a small peptide from the carboxy terminus. The small peptide, termed systemin, is mobilized through the phloem. Potato contains
two transcripts, potprol and potpro2. The transcript for Potpro2 was analyzed by RT-PCR and found to be expressed during infection by
Phytophthora infestans. Expression of the gene was localized near the site of infections. The transcript was cloned and used to
construct an antimicrobial peptide delivery system. Sequences for a 12 amino acid antimicrobial peptide was introduced into the
systemin-encoding region of the transcript. The construct is currently being tested under various promoters to test the ability of the
antimicrobial peptide to be effectively released into the phloem of potato.
Kazarian, Dodi E, Scott J Nissen and Asunta L Thompson. "Broadleaf Weed Control in Potatoes
with Sulfentrazone and Flumioxazin." [Vol. 77, 404]
Nightshades are the most common weed problems in potato production systems. Sulfentrazone and flumioxazin have demonstrated
activity on nightshades and were evaluated for selectivity in potatoes. Two field experiments were conducted in the summer of 1999 to
establish sulfentrazone and flumioxazin efficacy and potato varietal response. Sulfentrazone was applied at several rates, alone and in
combination with S-metolachlor and pendimethalin, while flumioxazin was applied alone and in combination with S-metolachlor. These
treatments were compared to standard potato treatments. Sulfentrazone and flumioxazin both provided excellent hairy nightshade, redroot
pigweed, and common mallow weed control in potatoes with no crop response. Low rates of sulfentrazone and flumioxazin in combination
with S-metolachlor provided excellent weed control, high yields, and high USDA#1 grading percentages. Sangre, Chipeta, Russet
Norkotah, and Russet Nuggets were used to evaluate cultivar response. Sulfentrazone was applied at 0.14, 0.21, and 0.28 kg
ha-1 and flumioxazin at 0.035, 0.053, and 0.07 kg ha-1.
Sulfentrazone treatments resulted in 35% and 13% phytotoxicity to Sangre and Chipeta varieties, respectively, however, this injury did not
result in yield loss. Flumioxazin treatments did not result in any significant injury or yield loss.
Kelling, Keith A and Phillip E Speth. "Effect of Cation Balance on Potato Yield, Quality and Tissue
Concentrations." [Vol. 77, 405]
Continued use of high rates of K for potato combined with increased applications of supplemental Ca, have raised questions as to the
need for additional Mg, especially on low cation exchange capacity soils. This experiment, at three Wisconsin locations, evaluated
interactive effects of high application rates of Ca and K on plant Mg levels, and examined the efficacy of broadcast or row-placed Mg in these
situations. Soil treatments of 2.25 Mg/ha CaSO4 or 6.72 Mg/ha of calcitic or dolomitic lime were applied
12 months prior to planting potato. At planting, the main plots were split into those receiving 0 or 269 kg K2
O/ha as KCl, K2SO4, or KMgSO4.
Although soil test Mg was marginal at two of three locations, apparently the addition of high levels of Ca or K did not cause major Mg
shortages. All sites responded to K, with the magnitude of the response related to initial soil test K levels. In most cases, there were no
statistically significant differences between the various sources of added potash. Where K was added as KMgSO4
, there tended to be slightly lower yields but somewhat larger percentage and larger size of grade A tubers. Surprisingly,
there was no clear cut advantage to using the KMag where the soil treatment did not include magnesium. It is possible that critical soil test
levels of 50 ppm on sands and 100 ppm on medium-textured soils may be very conservative. Plant analysis of both vegetative and tuber
tissue confirmed some antagonism between the various cations; however, at these levels, an adequate amount of Mg was apparently
present as the gypsum treatment with KCl applied showed at least 0.35% Mg in the leaflet and petioles.
Khu, Dongman and Hak-Tae Lim. "Establishment of Selection System To Common Scab Resistance
Potato Clones Using In Vitro Thaxtomin-A and Tissue Culture System." [Vol. 77, 405]
Thaxtomin-A (TA), phytotoxin produced by Streptomycese scabiese, has been known to be positively correlated with pathogenicity
of Streptomycese scabiese. This study was undertaken to know whether TA can be used for screening resistant lines against
common scabies at the early stage of the potato breeding program. We also used TA in an in vitro system for selecting mutated clones with
resistance to common scabies. Three cultivars, 'Superior' (resistance), 'Atlantic' (susceptible) and 'Shepody' (susceptible), were subcultured
on the MS medium supplemented with 0.0001, 0.001, 0.01, 0.1, 0.5, and 1mg/L of TA for three weeks. Shoot heights of each cultivar were
measured to determine the suitable levels of proper concentration for in vitro selection, and shoots of 'Superior' were grown better at higher
concentration of TA while those of 'Shepody' were very short or dead depending on the levels of TA in the medium. True potato seeds (TPS)
derived from cross between Superior and Atlantic were germinated, multiplied, and tested for their resistance level on MS medium containing
0.5mg/L of TA for five week. All of tested seedlings under in vitro condition were transplanted on scab infested soil and were evaluated for
scab symptom using scale 1 to 5 (1=no scab, 5=>80% scabby surface). About 400 germplasm lines derived from cross between resistant
lines and susceptible ones, were planted in heavily populated soil with common scabies, and 24 lines were found to be very resistant to
common scabies. These resistant lines have been introduced in vitro TA system and analyzed for their correlation between TA and field
systems. Somaclonal variants and mutants were induced using mutagen and in vitro regeneration system, and these clones are being
examined for their resistance to common scabies.
Kirk, William W, Kathleen Baker, Brendan A Niemira and Jeffrey M Stein. "Epidemiology
and Chemical Control of Phytophthora infestans in Potato Canopies Following Point-Source Inoculation."
[Vol. 77, 405]
Point-source inoculations with the US-8 biotype of potato late blight (Phytophthora infestans mont. De Bary) were made in potato
fields that were either unprotected or were treated with chlorothalonil-based or cymoxanil-based fungicide programs. In a three year study,
spatially distributed foliar disease observations were made in test plots during the course of each season. Rate of increase of foliar infection
and pattern of late blight spread and the efficacy of different fungicide control strategies were determined with RAUDPC calculations for each
quadrant and regression of percent infected plot area against time. Late blight spreads more quickly along rows than across rows in
both fungicide protected and unprotected plots. Late blight severity in unprotected foliage decreased with distance from the site of
inoculation, while severity in fungicide protected foliage decreased less. Curative applications of chlorothalonil-based programs on a
weekly schedule beginning 7 days after inoculation or cymoxanil-based programs initiated 24, 48 or 72 hours after inoculation slowed initial
development of late blight, but did not ultimately prevent spread throughout the plot. Once late blight is present in the plot, the area of canopy
at actionable disease levels (7 % foliar infection) increases at the rate of 15-22m2/day in unprotected plots, and at 12-15 m2/day in fungicide
protected plots. A single prophylactic application of chlorothalonil 7 days before inoculation delayed, but did not prevent, widespread
disease development across the plot. A chlorothalonil program beginning 7 days before inoculation and continuing on a weekly schedule
throughout the season was most effective at suppressing late blight development.
Kuhl, JC, RE Hanneman, Jr. and MJ Havey. "Genetic and Molecular Characterization of Late
Blight Resistance in a 2X(1EBN) Mexican Species, Solanum pinnatisectum." [Vol. 77, 406]
Mexican diploid potato species with an Endosperm Balance Number (EBN) of one have long been recognized as sources of late blight
resistance, but attempts to transfer this resistance to the 4x(4EBN) level have been hampered by crossing barriers, limiting utilization and
characterization of this resistance. Recent changes in Phytophthora infestans populations have increased interest in utilizing new
sources of resistance to late blight. We characterized late blight resistance in Solanum pinnatisectum to facilitate incorporation this
and other 2x(1EBN) resistances. Resistance to P. infestans in 2x(1EBN) wild potato germplasm included individuals from S.
cardiophyllum subsp. cardiophyllum (cph) and S. pinnatisectum (pnt). Replicated detached leaf tests using a US-8, A2
P. infestans isolate detected susceptible and resistant individuals within both species. F1 hybrids
from an interspecific cross between a resistant S. pinnatisectum and susceptible S. cardiophyllum segregated for resistance
1:1. A backcross family was generated between a resistant F1 and the susceptible S. cardiophyllum
parent. Segregation of 42 resistant to 57 susceptible BC1 progeny supports a single dominant locus
conditioning resistance. Marker analysis was conducted using RFLP clones uniformly distributed over the genome. The resistance locus
was mapped to the long arm of chromosome 7, a region previously unassociated with resistance to P. infestans.
Lagnaoui, A, V Canedo and DS Douches. "Evaluation of Bt-CRYV Transgenic Potatoes on Two
Species of Potato Tuber Moth, Phthorimaea operculella (Zeller) and Symmetrischema tangolias (Gyen) in Peru."
[Vol. 77, 406]
The Potato Tuber Moth, Phthorimaea operculella (Zeller) is one of the most damaging potato pest in tropical and subtropical areas.
Damage is often observed on potato foliage, stems and tubers. Although yield loss seldom occurs from PTM field infestations, quantity
and quality losses in storage are rather drastic in warmer climates where losses can reach 100%. A second species of potato tuber moth,
Symmetrischema tangolias is also a serious potato pest in the Andean region. Several control components have been identified for
both pests. Among these, the use of Bacillus thuringiensis that proved effective in reducing PTM infestations in stores. So far, host
plant resistance work has not yielded any promising material with appreciable levels of resistance. The expression of the Bacillus
thuringiensis genes confers a non-conventional host plant resistance to this pest. The objective of this is to test the effect of Bt-cryV
potato transgenic plants on the two species of potato tuber moth in Peru. Detached leaves bioassays were carried out using 10 neonate
larvae per replication on each transgenic lines of the cultivars, Atlantic and Spunta. Mortality in Atlantic transgenic plants was lower for P.
operculella, ranging from 18 to 34%, than for S. tangolias, ranging from 82 to 94%. In the case of transformed Spunta, all lines
tested, showed high levels of mortality in both species. Mortality ranged between 80 and 98% for both species. The Bt-cryV gene offers
another source of resistance genes, which can be pyramided for effectiveness toward the development of durable resistance to potato tuber
moths and other insect pests.
Landeo, Juan A, M Gastelo, E Roncal and A Mendoza. "Phenotypic Stability for Horizontal
Resistance to Potato Late Blight in Population B." [Vol. 77, 406]
Population B is a potato breeding population under improvement for horizontal resistance to late blight in absence of major genes
(R genes), agronomic and quality traits for table and industry, tolerance to other biotic and abiotic stresses and adaptation to major
agro-ecologies in short-day developing countries. A sample of 26 clones of this population from recombination cycle one (B3C1) with
different levels of resistance, were tested against late blight during seven seasons in four locations within Peru to determine their phenotypic
stability for resistance. A standard randomized complete block design with three replications of 10-hill plots was used for all locations.
Disease infection was natural in each location and percent of foliage infection was recorded for six consecutive weeks. Blight severity
during 1998 was unusually high due to heavy rainfall resulting from El Nino phenomenon and the pathogen population corresponded to the
new type (E-1), but all A1. The area under the disease progress curve (AUDPC) was used as a parameter for resistance and to rank genotypes
in all locations. Non-parametric statistics involving the variance or standard deviation of the ranks of a genotype in different environments
were used to determine the phenotypic stability of clones under. Results indicated stable performance of all clones for resistance to late
blight overall environments. However, there may be some differences of stability among genotypes. It can be concluded based on this
preliminary study that late blight resistance under improvement in this population is stable across environments and that genotype x
environment interaction is not so important. Breeding implications for resistance to late blight will be discussed.
Leary, Beth, David S Douches, and Ray Hammerschmidt. "Expression of the Grapevine Stilbene
Synthase Gene in Potato to Build Resistance to Late Blight." [Vol. 77, 407]
Late blight, caused by Phytophthora infestans (Mont.) deBary, is the most serious disease of potato (Solanum tuberosum
subsp. tuberosum) in the U.S. The appearance of the more aggressive US-8 strain of P. infestans, resistance in this pathogen
to metalaxyl, and the potential loss of protectant fungicides is evidence of the serious nature of this problem. Successful, long term control of
this disease will require a combined effort that will incorporate the use of carefully managed fungicide programs, resistant varieties
developed through breeding, and the use of novel resistance mechanisms achieved via genetic engineering. Expression of the grapevine
resveratrol synthase gene may provide a means to increase late blight resistance. Our goal was to transform susceptible potato lines to
express the resveratrol synthase gene, evaluate the level of late blight resistance using a greenhouse-based disease resistance screen,
and provide molecular and biochemical characterization of transgene expression. Using Agrobacterium-mediated transformation
we have obtained eight and 29 transgenic Atlantic and MSE149-5Y lines, respectively. These plants are currently being grown for late
blight greenhouse disease tests and for the evaluation of resveratrol production. Comparisons will be made between non-transgenic lines
and their resveratrol synthase-transgenic derivatives. Data will be presented. If it is found that these transformed plants have increased
resistance to late blight, the resveratrol synthase gene could be used to enhance late blight resistance in current and future cultivars.
Li, Xiu-Qing. "Source of DNA Polymorphism Detected by SSR-PCR in Potato."
[Vol. 77, 407]
DNA simple sequence repeats (SSR), or microsatellites, have been widely used in genome mapping and variety fingerprinting due to
the simple co-dominant inheritance of the SSR polymorphism. The source of the DNA polymorphism is an over-looked research area
although the common assumption is that the polymorphism is from the variation of the copy number of the SSR repeats. In the
present report, polymorphic fragments amplified by PCR from three SSR regions in potato Solanum tuberosum) were sequenced to
investigate the source of the polymorphism. The three SSR regions were the AATT5 repeats from the patatin gene, the CT13AT18 from
a proteinase inhibitor gene, and the C17...CT8 AT9 from another proteinase inhibitor. We have observed that the polymorphic variation
between two fragments amplified by a pair of primers flanking the patatin SSR region from two varieties is not from the copy number
changes at the SSR repeats but from the non-SSR sequences. For the two proteinase inhibitor genes, polymorphic variations are from
both the SSR repeats and the non-repeat sequences. Indirect evidence indicate that the primer regions were also a source of variation
detected by SSR-PCR in patatin genes. In summary, the results indicated that the DNA polymorphism detected by SSR-PCR in potato
varieties has three sources: 1) length variation at the non-SSR sequences, 2) length variation at the SSR sequences, and 3) primer-template
mismatches.
Li, Xiu-Qing , George CC Tai and Henry De Jong. "Association of Molecular Markers in Parents
with the Performance of Processing Quality Traits in Their Progenies." [Vol. 77, 407]
Fourteen hybrid families were obtained from crossing seven female parents with two male parents. The female parents included one
diploid (2x) genotype (CH72.03) and six tetraploid (4x) genotypes {F58089, F66041, F81109, B5141-6 (Lenape), Niska, and Shepody}.
The male parents (09571-03 and 09901-01) were diploid (2x) and produced 2n gametes via FDR. Forty 4x progenies from each cross
combination and their parents were used for field experiments conducted at the Potato Breeding Substation, Benton-Ridge, New Brunswick,
in 1997 and 1998. A number of quantitative traits were scored for all individual genotypes. Thirty-six microsatellite DNA markers showed
segregation of banding patterns among the nine parents. The bands showed different degrees of intensity. The banding patterns were
scored from 0 (no band) to 4 (brightest). The scores were subjected to the factor analysis to identified marker groups that may cast strong
effects on the means of quantitative traits of the 14 families. One factor accounted for more then 50% of the variability of the markers SM2,
SM5 and SM36. The scores of parents on this factor showed high correlations with the cross means of specific gravity (r = 0.72), glucose
content (r = 0.94) and color index of chips (r = 0.90). A small sample of 58 progenies were used to obtain their banding pattern of the
marker SM36. The mean values of glucose content, chip color, and specific gravity were significantly different between DNA marker classes
at p < 0.01, p < 0.01, and p = 0.10 levels, respectively.
Lim, Hak-Tae and Cheol-Soo Yoon. "Effective Treatment of Plant Growth Regulators on the Production
of Potato Mini-Tubers Based on Hydroponics System." [Vol. 77, 408]
This study was investigated to know the effect of the plant growth regulators (GA3 and PBZ) on the mini-tuber production using
hydroponics solutions. One potato cultivar "Atlantic" and one breeding clone #8 were used in the experiment. They were cultured
in the in vitro condition of MS medium supplemented with 3% of sucrose for three weeks. Tissue cultured seedlings were
transplanted in the pot (size, 18cm) containing various types of the soil mixtures such as perlite and horticultural composite. Hydroponics
system was button type using nutrient solution of "Alpine B". Seedlings were treated with GA3 (50-100 mg/L) and Paclobutrazol
(PBZ:50-150 mg/l) after 30 days and 38 days of transplanting, respectively. Different growth patterns such as leaf thickness and color and
height. Numbers of mini-tubers produced in each experiment were quite different, depending on the soil mixture and level of
plant growth regulators. More tubers were produced in the PBZ treatment of 150 mg/L (14 per plant) and GA3 of 10mg/L (11.25 per plant),
while the control plant had 7.6 per plant. Thus, treatment of plant growth regulators at the proper time combined with hydroponics system
can improve the almost two fold of the mini-tuber production.
Lim, Hak-Tae and Dongman Khu. "Selection of Resistant Potato Clones to Hollow Heart and
Internal Brown Spot Under Physiologically Disordered Field Conditions." [Vol. 77, 408]
'Atlantic' is the only chipping potato cultivar in Korea, but physiological disorders such as hollow heart (HH) and internal brown spot
(IBS) have been the major limiting factors in the increase of the production. The first step we did for screening resistant lines, was set up
for the field condition in which very high frequency of the physiological disorders (HH & IBS) in 'Atlantic' took place by various treatments
of periodic shading, and mulching, and plant growth regulators such as Trinexapac-ethyl(Te-E) and Dicloprop-triethanolamin (DTA). IBS
occurred as high as 67.5% in the field plot mulched by transpicuous film and shaded for 80days. The highest level of HH was 22.9% in the
plot mulched by transpicuous film and shaded for 60day one week after. Very high level of IBS (66.25%) also occurred in the plot treated by
1500mg/L of Te-E 40day after planting, while HH occurred at 21.3% in the plot treated with 1000mg/l of DTA 70days after planting. Under the
very heavily physiologically disordered field condition (combination of 1500mg/L of Te-E after 40 days of planting and 1000mg/L of DTA after
70 days of planting), 400 of clones at third seedling generation were tested, and 28 clones were found to be very resistant to HH and IBS,
while even 'Superior' and 'Jopung', known to very resistant, showed the quite high frequency in HH and IBS occurrence under disordered
field condition.
Lim, Hak-Tae, YS Song, DM Khu, CK Lim and JK Choi. "Evaluation of Somatic Hybrids
Derived from Solanum etuberosum and S. tuberosum Based on Morphological Characters and Disease Resistance."
[Vol. 77, 408]
We evaluated the 26 somatic hybrids obtained from the protoplast fusion between Solanum etuberosum Lindl and haploid line
of S. tuberosum "White lady". Various shape and size in leaf were detected, especially clone 5-3 showing almost all types
of leaf structures such as secondary leaflet, tertiary leaflet, asroscopic leaflet, basiscopic leaflet, and semi-basiscopic leaflet. However, clone
2-3 had 4 pairs of primary lateral leaflets. White lady was very small and weak which is a typical growth characters in dihaploid clones, but
hybrid plants grew up very vigorously, suggesting that somatic hybrids showed hybrid vigor. S. etuberosum, belonging to
ETUBEROSA, did not bear tubers, while the somatic hybrids formed small tubers, while parental plant (21white lady) had large tuber. The
tubers formed in somatic hybrids had a lot of eyes on their surface that is one of the typical stolon characters of S. etuberosum.
Based on bacterial wilt resistance using Pseudomonas solanacearum (PI498311) and in vitro tissue culture system for three
weeks, somatic hybrid clones of WE-2-1, WE-5-9, WE-5-21, WE-7, and WE-13 showed the medium level of the resistance. Somatic
hybrids also showed the various levels of PVY resistance, demonstrating that highly heterozygous clones can be obtained and used in the
potato breeding and germplasm enhancement program.
Lozoya-Saldaña, H and José Luis Caballero. "Tuber Blight by Phytophthora infestans in
Potato Genotypes." [Vol. 77, 408]
Washed and unwashed potato tubers were eye-inoculated with 10-12,000 sporangia/ml of P. infestans, followed by a six-week
incubation period either in a moist chamber, in a sterile soil mix, or in a naturally infested soil. Most tubers became infected in the
moist chamber regardless of the genetic foliage resistance of the genotype. However, more diseased tissue was observed in washed than
in unwashed tubers, as a possible microbial antagonism against infection from the "tuberosphere" of the dirty tubers. No
differences in degree of infection were observed when comparing incubation in sterile vs. natural soil nor clean vs. dirty tubers. Differences
were evident, though, among genotypes. D8-330, Cruza and Kartel, foliage-resistant to late blight, were tuber-resistant. Norteña and Rosita,
also foliage-resistant, resulted in high tuber infection. Alpha and Atlantic, foliage-susceptible to the pathogen, were tuber-susceptible too.
Clone J101K6, with partial foliar resistance also resulted in moderate tuber infection. The known durable genetic foliage resistance was not
necessarily reflected in the tuber, and in this assay the soil did not play an important role in infection. Resistance evaluations in both
foliage and tubers are required for a better characterization.
Lozoya-Saldaña, H and Alejandro Hernandez. "Genotype Environment and Standard
International Field Trial (G x E and SIFT) in Toluca, Mexico." [Vol. 77, 409]
Two experimental plots were established in the INIFAP-ICAMEX-PICTIPAPA Experiment Station in the Toluca Valley in 1999. For the
G x E study 13 materials were planted in 1998 and six additional genotypes were included in 1999 without fungicides. Susceptibility to late
blight increased considerably in 1999 for all materials with respect to the previous year. Consequently, tuber yield drastically decreased for
most genotypes. Cultivars Stirling, Torridon, and clone 720049 maintained their relatively high tuber production in 1999 (near 1 kg/pl) with
53, 20, and 15 % infection respectively. Bintje, Great Mountain, 96LBH1-25, and 96LBH-33, were very susceptible in both years. For SIFT 25
genotypes, with and without fungicides, were planted for the first time in 1999. Foliar infection ranged between 5 and 15% in the plots with
fungicides, and cvs. Stirling, Bionta, and Torridon produced higher tuber yields than the rest of the materials. When unprotected from late
blight Norteña, LBr-20, Cruza 148, and Idiafrit, were the least diseased, with less than 30% foliage infected, but Stirling, Norteña, and
Rosita were the best in yields; 933, 675, and 418 g/pl with 53, 22, and 38% infection, respectively. Pampeana-Inta, Teena, and Bionta
were the most susceptible to late blight. A relationship was not observed between disease severity and tuber yield.
Lu, Wenhe, Kathleen Haynes, Eugene Wiley, and Beverly Clevidence. "Colorimetric and Carotenoid
Analysis in Diploid Potatoes." [Vol. 77, 409]
The yellow pigment in potato tuber flesh is caused by various carotenoids which may protect against cancer, cardiovascular disease
and macular eye degeneration. This research was carried out to identify and quantify the carotenoids in 11 diploid clones of Solanum
phureja - S. stenotomum that produced at least 5% 2n pollen and two cultivars ('Yukon Gold' and 'Superior'), and determine the
relationship between the tuber yellow intensity and carotenoid content. Yellow intensity was determined by a colorimeter programmed to
calculate a yellowness index. Carotenoid analyses were performed on an automated HPLC system with software for integration and
quantitation with detection at 450 nm using a diode array detector. Six different carotenoids were detected: neoxanthin, violaxanthin,
lutein-5,6-epoxide, lutein, zeaxanthin, and an unknown carotenoid. The total carotenoid content in the yellow-flesh diploid clones was 3 to
13 times higher than 'Yukon Gold' and 4 to 23 times higher than 'Superior'. Both total and individual carotenoids were positively correlated
to the tuber yellow intensity. This suggests that selecting for more intense yellow-flesh will result in higher levels of carotenoids. These
yellow-flesh diploid potato clones have the potential to make significant contributions to improving the nutritional status of tetraploid potatoes
through 4x-2x hybridizations.
Ludy, RL and ML Powelson. "Early Season Foliar Fungicide Applications Delay Progression of Late
Blight of Potato." [Vol. 77, 409]
Timing of a foliar fungicide mixture after sporulation of Phytophthora infestans from a point source was evaluated for control of the
spread of late blight. One plant in the center of isolated plots (6 x 6 m) of cv 'Russet Norkotah' was inoculated with P. infestans (US-8)
when plants were 20 cm tall. Treatments were no fungicide or fungicide (cymoxanil (0.14 kg/ha) plus chlorothalonil (1.26 kg/ha)) applied
beginning 1) immediately (sprayed 2, 10, and 18 days after sporulation of the inoculated point source), 2) delayed (sprayed at 10 and 18 days),
or 3) late (sprayed at 18 days). Plants every 86 cm in four directions from the point source were evaluated weekly for late blight. At 3-wks
after point source sporulation, disease was observed at 86 cm from the point source in the delayed, late and no fungicide treatments, but
not in the immediate treatment. Initial lesions were observed on axillary buds (71%), stems (18%), petioles (7%), or leaves (4%). At 4-wks,
no lesions were observed in the immediate treatment at distances > 86 cm. In the other treatments, lesions were found most frequently
on leaves (65%), followed by axillary buds (22%), petioles (8%), and stems (5%). Lesion counts were significantly lower (P < 0.05) in the
delayed treatment compared to the late and no fungicide treatments at 86 and 172 cm. The three treatments were not significantly different
at 258 cm. At 5-wks, foliar blight severity on a per plant basis was < 2% in the immediate and delayed treatments, but had rapidly
increased to 13-21% in the late and no fungicide treatments at all three distances. Early season fungicide sprays are effective at delaying
the spread of late blight.
Lulai, Edward C and Thomas P Freeman. "Inhibition of Wound Induced Suberization in Potato
Tuber (Solanum tuberosum L.)." [Vol. 77, 409]
Native periderm, the dermal tissue of potato tuber, provides an essential barrier to pathogens. The cell walls of the outer group of
peridermal cells, phellem cells, are laminated with suberin, a complex, inert biopolyester, which provides a protective barrier for the tuber.
Suberin is composed of two distinctly different biochemical components; a polyphenolic component and a polyaliphatic component.
Tubers entering storage and cut seed tubers require rapid suberization of wounded areas to avoid disease and excessive shrinkage.
Despite the importance of wound induced suberization, very little is known about the biochemical mechanisms that regulate suberization.
We have investigated processes that may be involved in these regulatory mechanisms. Certain periderm and wound related metabolites
were found to have drastic effects on suberin polyphenolic accumulation. Delay of polyphenolic accumulation also inhibited subsequent
suberin polyaliphatic accumulation. Coumarins, which have been shown by others to be present in native periderm and possibly linked to
some peridermal diseases, were potent inhibitors of suberin polyphenolic accumulation during wound healing. The coumarin esculetin
inhibited peroxidase activity, a key enzyme in suberization. These results are important in determining what factors influence and regulate
suberization and the development of resistance to infection.
Lynch, Dermot R, Gerry C Kozub and Lawrence M Kawchuk. "The Relationship Between Yield,
Mainstem Number and Tuber Number." [Vol. 77, 410]
Using data from an eleven year period, total and marketable yield were related, using regression analysis, to mainstem and tuber
number for five maincrop varieties (Russet Burbank, Shepody, Atlantic, Norchip and Norland) and two early maturing varieties (Conestoga
and Carlton), at irrigated and dryland sites in western Canada. Mainstem number by itself is a poor predictor of total and marketable yield.
Highly significant regressions of yield on the derived variable tuber number per mainstem were evident for all cultivars grown at the dryland
sites. In general, the proportion of the total variation in yield accounted for by the regression models was much higher at the dryland than
at the irrigated sites, indicating that the relationship between yield and its predictor variables are more complex for the irrigated sites. While
the study suggests that the use of tuber number per mainstem may be useful as an early season predictor of tuber yield for cultivars,
particularly under dryland conditions, a model using the predictor variables mainstem and tuber number will generally be superior due
to the additional information it provides when competitive effects for light energy within the canopy or among developing tubers are present.
Contour plots provide a useful way to study the effect of changes in tuber number at specific stem density levels on the yield response.
Malkawi, AA, BL Jensen and Alan R Langille. "Isolation of Several Plant Hormones from 'Katahdin'
Potato Plant Tissues and the Influence of Induction on Their Levels." [Vol. 77, 410]
Using high performance liquid chromatography and combined gas chromatography-mass spectrometry, gibberellic acid (GA-3) and
several cytokinins including, cis-zeatin riboside, trans-zeatin riboside, trans-zeatin and isopentenyladenine were isolated from
"induced" and "non-induced" 'Katahdin' tissues and quantified. Similarly, certain jasmonates including, jasmaonic
acid, tuberonic acid and its methly ester and 9,10-dihydromethyljasmonate were also identified. The cytokinins and jasmonates generally
increased under "inducing conditions" while levels of GA-3 were observed to be elevated under "non-inducing
conditions". The possible roles of these natural products in the tuberization process(es) of the potato will be discussed.
Meredith, Peter. "A Century of Tuber Density Technology, but Not Much Science."
[Vol. 77, 410]
Cultivar genetics may not be the main determinant of tuber density. Growing conditions have a large influence, while density (= starch,
other solids and intercellular space) of an individual tuber varies during growth and with tuber size. Consumer quality has only an
association with percentage solids; it is not causal. Nevertheless, as Coudon and Bousard described in 1897, density or specific gravity
is a successful predictor of cooking or processing quality of potatoes and is equally successful as a predictor of their dry matter content as
a forecaster of yield of processed products. But these are only predictions, a technological concept for which we have little scientific
basis - we have the know-how but not the know-why. Yet repeatedly we see industry spending money in their laboratories in wasteful search
for meaningless precision of correlations. Numerically, both density and dry matter are arbitrary determinations dependent on how the
sample has been treated and how the measurement is made. And the same old variables of season, cultivar, growing and harvesting
conditions, storage, transport and sampling will always apply. Of course the detailed approximate relationships will differ, so why not just
use the tables in one of the textbooks and save the waste of time and money. There will always be considerable scatter of experimental
points, but most of that scatter is not symmetrical about the line of relationship, since lowering of density by the readily varying intercellular
space is the major variable. The relationship is not necessarily a straight line, either. Tuber structure suggests why, and tuber development
studies provide much further explanation.
Mikitzel, Loretta and David Wattie. "Greensprouting Seed Tubers to Improve Early Yield."
[Vol. 77, 411]
Greensprouting, (aka chitting or presprouting), involves exposing seed tubers to light in a warm environment to develop short, strong,
green sprouts before planting. The response of Red Pontiac, Chieftain and Kennebec to greensprouting was studied in 1999. Whole seed
tubers were greensprouted for 8 weeks under natural light prior to planting on June 5. Control tubers were held in the dark at 4C. All tubers
were hand-cut the day before planting. With each cv. tested, greensprouted tubers emerged earlier than control tubers. Greensprouting
decreased Red Pontiac stem and tuber numbers and had no effect on total yield after 69 days when plants were grown with 90 kg N/ha.
Chieftain stem and tuber number per plant were unchanged by greensprouting. When plants were topkilled 69 days after planting total yield
from greensprouted Chieftain seed was 2.9 t/ha higher than control plants. Greensprouted Kennebec seed produced plants with more
stems than control plants. Tuber number was not affected by greensprouting and total yield was increased by 28% to 25.9 t/ha by 69 days
after planting. Chieftain and Kennebec yield increases after greensprouting were due to higher yield of tubers >51 mm in diameter.
Average tuber weight of all 3 cvs was increased by greensprouting. Greensprouting conditions must be managed properly to improve early
season yields.
Miller, Jeff, Terry Miller, Nora Olsen and Phil Nolte. "Frequency of Late Blight Fungicide Use in
Southern Idaho During 1998 and 1999." [Vol. 77, 411]
Data on fungicide use were obtained from potato growers and commercial field representatives in southern Idaho for 127 fields in 1998
and 129 fields in 1999. The average number of late blight fungicide applications made per field was 7 in 1998 and 7.5 in 1999. Mancozeb
based products were used on 85 percent of all fields an average of 5.5 times per field. In contrast, chlorothalonil based products were used
on 23 percent of all fields an average of 2.3 times. During 1999, mancozeb based protectants were applied on 96.1 percent of fields an
average of 6.8 times while chlorothalonil was applied to 23.3 percent of potato fields an average of 1.6 times. Section 18 materials (Tattoo
C and Acrobat MZ) were not widely used in 1998 and their usage was not reported in 1999. Cymoxanil and triphenyl tin hydroxide were the
most widely used in 1998 (74.8 percent and 63.8 percent of all fields, respectively). In 1999, when late blight was not observed in most of
southern Idaho, cymoxanil and triphenyl tin hydroxide use dropped sharply (8.5 and 39.5 percent of all fields, respectively).
Mills, Dallice and Brian W Russell. "Use of Species-Specific Primers for Concomitant Verifiable
Detection of Clavibacter michiganensis Subsp. sepedonicus and Elimination of False Negative Reactions by Multiplex PCR."
[Vol. 77, 411]
Populations of the bacterium Clavibacter michiganensis subsp. sepedonicus (Cms), which cause bacterial ring rot of
potato, are known to exist at levels in planta that produce no visible external symptoms and, also, below the threshold of detection
with current immunodetection procedures. Stringent worldwide sanitation standards currently impose a zero tolerance level for the presence
of Cms in commercial potato seed tubers. To ensure a greater probability of producing Cms-free seed tubers, we have developed a
verifiable detection system based on multiplex PCR amplification of three single copy, dispersed Cms-specific DNA sequences, Cms50,
Cms72, and Cms85. To counter inhibition of the polymerase enzyme that frequently occurs from soil contamination and plant cell components,
acid hydrolyzed casein is added to the reaction. To verify that the Cms-specific primers are functioning in the presence of PCR inhibitors,
each sample also contains approximately 4 femtograms of a sea anemone DNA fragment that was modified so it can be amplified from
primers that amplify the Cms-specific, Cms72 DNA. In the absence of both inhibition and Cms DNA, the sea anemone fragment is amplified
in stem and tuber samples. However, even in the presence of low levels of Cms, the three Cms fragments are preferentially amplified
without amplification of the sea anemone fragment. When hydrolyzed casein occasionally fails to counter polymerase inhibition, no DNA
fragments are amplified. Dilution of these samples effectively relieves the inhibition, and multiplex PCR amplification of either Cms
fragments or the sea anemone fragment is readily accomplished, thereby eliminating the occurrence of false-negative reactions.
Mills, Dallice, Jessica M Schrunk, Brian W Russell, Philip B Hamm and DA Johnson.
"PCR-Based Mitochondrial Haplotying of Phytophthora infestans Populations in Oregon and Washington."
[Vol. 77, 412]
PCR amplification of two regions in the mitochondrial genome of P. infestans followed by digestion of the PCR products with
restriction enzymes Msp1 and EcoRI was shown by other researchers to produce four patterns or haplotypes that were designated Ia, IIa,
Ib and IIb. Using multiplex PCR, 320 isolates recovered from potato fields in Oregon and Washington from 1992 through 1999 were
analyzed, and they could be classified as Ia, Ib or IIb; no IIa haplotype was detected. Of the viable strains in the 1992 collection, 6 were A1
(1b) and one was A1 (IIb). Nine of the 18 A1 isolates from the 1993 collection had the Ia haplotype, which was not previously observed
in the 1992 collection. The A2 mating type first appeared in 1993, and 4 of 6 isolates examined were also haplotype Ia. Of interest was
the observation that the remaining 2 isolates of A2 mating type had the IIb mitochondrial haplotype, characteristic of strains of A1 mating
type in 1992. The A2 (IIb) genotype was never detected again among 257 A2 isolates examined from 1994 through 1999; all were A2 (Ia).
Among 46 A1 isolates examined from 1993-1997, 23 were A1 (Ia), 8 were A1 (Ib) and 15 were A1 (IIb). These findings are consistent with
other recent work suggesting that either mating occurred between sexually compatible strains in the 1993 population to produce A1 (Ia) and
A2 (IIb) recombinant genotypes, or strains of these genotypes were introduced on seed. Moreover, the population has stabilized since
1995 with greater than 90 percent of the isolates being of one genotype, A2 (Ia), and the remaining being either A1 (Ia) or A1 (IIb).
Mujica, N, F Cisneros and A Lagnaoui. "An IPM Strategy to Manage the Leafminer Fly, Liriomyza
huidobrensis (Blanchard) on Potatoes in the Canete Valley of Peru." [Vol. 77, 412]
The pea leafminer fly, Liriomyza huidobrensis (Blanchard) is a destructive, polyphagous insect pest of potato and several other
vegetable crops in the tropics and subtropics. The genus Liriomyza is believed of Neotropic origin and was restricted to the New
World until the mid 1970s. But since then, these species are rapidly spreading to other areas, and are presently reported in several
countries of Latin America, Africa and Asia. The International Potato Center has been involved in the development of integrated
pest management practices using host plant resistance and parasitoids, which have been found to be effective in keeping leafminer, fly
populations at sub-economic levels in the Canete Valley. In this case farmers were drawn on a pesticide treadmill, 10-13 sprays per
season are used against leafminer flies in potato fields. The cost of spraying is one of the highest inputs in potato production. This paper
reports on Leafminer fly dynamics, seasonal history, plant-insect interaction (with special emphasis on the mechanism of egg-extrusion),
development of resistant potato clones, the occurrence and potential efficacy of the complex of natural enemies and the selective use of
larvicides. Preliminary results show that substantial reductions in chemical applications have been achieved in potato fields primarily by
shifting away from non-selective adulticides, adopting translaminar larvicides and using of yellow sticky traps. The problem of the leafminer
fly in the Canete valley is a valuable case study of the vulnerability of intensive potato production to new pests, particularly when the crop is
grown outside of its agro-ecological range.
Newberry, George D and Robert E Thornton. "The Effect of Cultivar and Tuber Size on the
Efficacy of Maleic Hydrazide for Volunteer Potato Control." [Vol. 77, 412]
Volunteer potato plants can be a very competitive weed problem in rotation crops following potatoes. Maleic Hydrazide (MH-30) is labeled
for both sprout control and volunteer plant suppression. Recent surveys have found many volunteer plants in fields of rotational crops
where the previous potato crop had been treated with MH-30. The objective of this study was to determine the effect of cultivar and tuber size
on MH-30 tuber residue and volunteer plant suppression. Potato plants of Norkotah, Shepody, Ranger and Russet Burbank were treated
with a foliar spray of MH-30 (3.4 kg a.i./hectare) when a majority of the tubers within a cultivar were greater than 2 inches in length. Tubers
were harvested and sized into four categories, 0-57, 57-113, 113-283 and >283 gm. Tubers were sampled for MH-30 residue or stored at
4.4 degrees C to be used as seed for a plant-back study. The 0-57 gm tubers, most common in potato leavings, had the lowest MH-30
residue in 1998 and 1999 regardless of cultivar. Thirty seven percent of the treated 0-57 gm tubers emerged in the 1998 plant back study.
The cultivar effect is less clear but Shepody had the highest MH-30 residues in both years in all of the size categories. MH-30 will prevent
sprouting and volunteer plant establishment in larger tubers of some cultivars, but MH-30 will not solve the volunteer problem and must be
used in conjunction with other control methods.
Nie, Xianzhou and Rudra P Singh. "Detection of Multiple Potato Viruses Using an Oligo (dT) as a
Common cDNA Primer in Multiplex RT-PCR." [Vol. 77, 412]
Multiplex polymerase chain reaction (M-PCR) accommodates several pairs of primers in one reaction, resulting in reduced material
costs and time when compared to several individual PCR reactions. Furthermore. during reverse transcription of viral RNAs. ascertaining
the desired concentrations of various reagents and primer combinations, which significantly affect the subsequent amplification process is
a lengthy process. Therefore, in cDNA preparation. a common primer for reverse transcription would be faster and more economical by
avoiding the complexities of adjusting the antisense primer ratio. A novel usage of multiplex reverse transcription polymerase chain reaction
(M-RT-PCR) for simultaneous detection of five viruses and a viroid is reported. By use of an oligo (dT). as a common primer, nearly full-length
cDNAs can be synthesized. Furthermore, combining an oligo (dT) primer with a specific antisense primer can be used to simultaneously
prime reverse transcription of both polyadenylated and nonpolyadenylated RNAs. Four viral genera including five potato viruses [carlavirus
(PVS). polerovirus (PLRV). potexvirus (PVX). potyvirus (PVA and PVY)] and a viroid genus including a viroid genome [pospiviroid (PSTVd)]
were used to develop various formats of M-RT-PCR. In artificially created viral RNA mixtures, all six RNA pathogens were successfully
detected by uniplex- and M-RT-PCR. In naturally infected field grown tubers. M-RT-PCR detected infection of 2-3 viruses. which were
present in the tubers.
Nie, Xianzhou and Rudra P Singh. "A Novel Usage of Random Primers for Multiplex
RT-PCR Detection of Virus and Viroid in Aphids, Leaves and Tubers." [Vol. 77, 413]
A multiplex reverse transcription polymerase chain reaction (M-RT-PCR) was developed for the simultaneous detection of five potato
viruses and a viroid. The synthesis of cDNAs used for amplification was primed by hexanucleotides (random primers). An RNA extraction
procedure employing DNase I, is routinely used to isolate potato viruses and viroid (potato virus S [PVS]; potato leafroll virus [PLRV]: potato
virus X [PVX]; potato virus A andY [PVA, PVY], and potato spindle tuber viroid [PSTVd]) from infected tissues. This extraction method produced
deoxy-oligonucleotides, which in turn were used to prime the reverse transcription of RNA templates of all the viruses and the viroid.
A time-course study from 0 to 30 min showed optimal oligonucleotide generation by DNase I occurred at 10 min, an incubation time already
incorporated in the extraction protocol. The presence of oligonucleotides capable of priming cDNA synthesis was also demonstrated in
RNA preparations from aphids, leaves and tubers. In order to duplicate the priming of templates by oligonucleotides, commercially available
hexanucleotides were used as random primers. When fragments were amplified from the 5'- and 3'-end ends of the random primed cDNA
of PVY genome, bands of similar intensity were observed. In contrast, when two fragments (short and long) from the P1 gene region
of the PVA genome were amplified, the yield of the short fragment was significantly higher in intensi