Development of sheath blight resistant genotype of rice by mutation breeding and gene expression profiling after inoculation of Rhizoctonia solani

Sheath blight (ShB) is one of the most economically devastating disease affecting rice (Oryza sativa L.) crop globally. It is caused by Rhizoctonia solani Kühn. Still, there is no rice variety available that is highly resistant to ShB. Mutation breeding is one of the potential options and very less explored to develop ShB-resistant cultivars. It introduces genetic variability in desired traits. In the present investigation, mutagen sodium azide 0.03% was used for mutation of the Swarna variety for the creation of variability of ShB resistance. All total 1000 M1 plants with control were screened for ShB resistance by artificial inoculation and based on disease scores of ShB 46 contrasting M2 lines for ShB resistance were selected. The M2 lines were screened under field and humid chamber conditions. In both conditions, mutant lines were performed consistently and identified highly resistant and susceptible ShB lines. A total of 7 contrasting M2 lines with control were used for protein expression analysis and resistant lines gave an extra band between 33 and 44 kDa. Further, it was confirmed by gene expression study these proteins were pathogen-related (PR) proteins and caused the tolerant nature of ShB resistant lines. Hence, this study provides ShB tolerant line that could be advanced and used for ShB resistant variety development. Overexpression of PR genes, which may be useful as targets for crop improvement is linked to disease resistance.