Towards molecular mapping for resistance to sheath blight (Rhizoctonia solani Kuhn.) in rice (Oryza sativa L.) and barley (Hordeum vulgare L.) genotypes

Sheath blight caused by Rhizoctonia solani Kuhn. [Teleomorph; Thanatephorus cucumeris (Frank) Donk.] causes extensive losses to rice crop in India. Our aim here was to compare sheath blight disease response of some rice and barley genotypes. Ten rice and five barley genotypes were inoculated with the highly virulent R. solani, isolate D-14 belonging to anastomosis group AGIIA. All the barley genotypes were immune against this isolate. Among rice genotypes, HR-12 was resistant while NDR-9930112 was moderately resistant where as genotypes NDR-9930077 and PB-1 were highly susceptible. Genomic DNA of rice and barley were amplified using NBS-LRR (Nucleotide Binding Site-Leucine Rich Repeat) based degenerate primers. Specific bands of approximately 380 bp and 190 bp were observed in rice and barley, respectively confirming that R-gene domains are present within rice and barley but vary in size. Interestingly a band of approximately 190 bp, of same size as that of barley (190) was also amplified in NDR 9930112 and HR-12 which were resistant to the test isolate. This band was absent in the highly susceptible cultivar PB-1 indicating that this region may be directly or indirectly related to the sheath blight disease resistance.