Resistance of Two Rice Cultivars to the Sheath Blight Agent Rhizoctonia solani AG1-1A

Contamination of ecosystems upon excessive use of pesticides and emergence of resistance in pathogens to these chemicals makes continuous research on development of new control methods and strategies to combat plant pathogens an essential task. Plant disease resistant genes are useful genetic resources that can be employed to develop resistant varieties as the best alternative to other control measures. The present investigation was carried out to analyze the interaction of two major rice cultivars grown in Northern provinces, with <em>Rhizoctonia solani</em>, the causative agent of rice sheath blight disease. Binam and Khazar known as the resistant and susceptible cultivars, respectively, were inoculated and their reaction to <em>R. solani</em> determined. The lesions in the sheath of the susceptible cultivar were twice in length compared to those on the resistant cultivar. Analysis of data by the Student’s T test showed existence of significant difference (P value < 0.05) between the two cultivars. To determine the expression profile of the genes involved in resistance to <em>R. solani</em>, samples were taken from leaves of two weeks old seedlings in different time courses post inoculation. RNA was extracted from the samples and analyzed by quantitative real time PCR. Results of the present study indicated that expression rates of <em>PR-5</em>, <em>Proxidase</em>, <em>PR-10</em>, <em>Defensin</em>, <em>Thionin</em>, and <em>NH-1</em> in resistant genotype (Binam) increased greatly after inoculation with <em>R. solani</em> when compared to Khazar cultivar. The outcomes of this study also suggest that the genes under study are involved in resistance mechanisms of rice against sheath blight disease.