COMPARATIVE ANALYSIS OF PUTATIVE VIRULENCE GENE EXPRESSION IN TWO RHIZOCTONIA SOLANI PATHOSYSTEMS

COMPARATIVE ANALYSIS OF PUTATIVE VIRULENCE GENE EXPRESSION IN TWO RHIZOCTONIA SOLANI

PATHOSYSTEMS

By Renee A. Rioux

Thesis Advisor: Dr. Stellos Tavantzis

A Lay Abstract of the Thesis Presented

in Partial Fulfillment of the Requirements for the

Degree of Master of Science

(in Botany and Plant Pathology)

August, 2010

            Rhizoctonia solani is a plant pathogen that, due to its extensive host range, has commonly been described as ‘infecting everything green.’  Many of the plants that fall prey to Rhizoctonia-induced disease are of anthropogenic importance for agricultural, economic, utilitarian, and aesthetic reasons.  Chief amongst these are rice (Oryza sativa)and potato (Solanum tuberosum), which represent the first and fourth most important crops for human consumption grown worldwide, respectively.  Sheath blight of rice caused by R. solani is the second leading cause of yield loss in most major rice growing areas worldwide.  Similarly, the R. solani-induced diseases stem canker and black scurf of potato can cause significant reductions in yield and quality, as well as interfere with seed certification. 

     Currently, little is known about the methods by which R. solani infects its multitude of hosts, particularly at the molecular level.  Such studies have been performed in a number of different host/pathogen systems and have provided valuable insight as to the genes and their products involved in pathogenesis.  This has improved understanding of the means by which these pathogens infect their hosts and enabled the development of highly effective methods for disease control and prevention in these pathosytems.  To this end, it was the purpose of the current investigation to determine genes potentially involved in R. solani pathogenesis and evaluate their expression during the early stages of infection.  A comparative study of the rice and potato pathosystems of Rhizoctonia was undertaken to allow for the identification of genes important for R. solani pathogenesis in general and not specific to a particular host.

          The results of this research indicate that a number of genes are similarly expressed by R. solani in both rice and potato during the early stages of pathogenesis.  Grouping of these virulence-associated genes based on their expression during early host-pathogen interaction suggests three key events are involved in the R.solani pathogenesis process: early host contact and infiltration, adjustment to the host environment, and disease proliferation through necrosis.  These findings serve as a basis for further studies on the molecular mechanisms of R. solani pathogenesis and will contribute to the development of improved methods for Rhizoctonia-disease control.