Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2003
Publication Date: 8/9/2003
Citation: Jia, Y., Singh, P., Cartwright, R., Lee, F.N., Rothrock, C.S., Eizenga, G.C., Rutger, J.N. 2003. Characterization of isolate diversity in the rice sheath blight pathogen rhizoctonia solani [abstract]. American Phytopathological Society Annual Meeting. 9-2003-0294-AMA.
Technical Abstract: Fourteen Rhizoctonia solani (rice sheath blight) isolates from five counties in Arkansas, the major rice-growing state I the United States, were characterized by anastomosis, nucleotide sequence of the internal transcribed spacer (ITS) region and pathogenicity assays. Imperfect hyphal fusion with an AG1-IA tester indicated that all 14 isolates belonged to the AG1-IA group. Phylogenetic analysis of nucleotide sequence of rDNA-ITS revealed three classes of the pathogen isolates with minor nucleotide substitutions. Sequences of a major class of rDNA-ITS (9 isolates) were identical to the sequence of rDNA-ITS of isolates from Vietnam and the Philippines. Virulence of the pathogenic isolates toward rice cultivars was evaluated by a detached leaf inoculation method. The second youngest leaves of greenhouse-grown rice plants were detached and inoculated with potato dextrose agar plugs containing hyphae and incubated in petri dishes Most virulent, moderate virulent and least virulent isolates were determined three days after inoculation. Differential responses of rice cultivar leaves toward the isolates were also detected by this method. No correlations between nucleotide sequences of rDNA-ITS and virulence of the pathogen isolates were evident. Characterized R. Solani isolates should facilitate the development of rice cultivars that are more resistant to sheath blight.