Inheritance of sheath blight disease resistance in submergence rice (Oryza sativa L.)

Sheath blight caused by Rhizoctonia solani Kuhn is one of the important diseases of rice, resulting in heavy yield loss in rice every year. Genetic nature of sheath blight has been found to be complex and controversial issue in the earlier studies. There were some reports about the major gene conferring resistance to sheath blight. Non allelic dominant major resistance gene was also reported in resistant cultivars. A total of 50 QTL associated with sheath blight resistance located on all 12 rice chromosomes have been reported, with 10 of these co-localizing with QTL for morphological attributes, especially plant height, or for heading date. The objective of this paper was to see inheritance pattern of sheaath blight. All the plant in the F₁ shown resistant reaction with 22.25% disease severity, and in F₂ population the resistant or moderately resistant, and susceptible in the ratio of 3R/MR: 1S which is mainly due to presence of dominant effects of resistant QTL/genes qSBR11-1. The F₃populations were classified into resistant, moderately resistant and susceptible in the ratio of 3: 2: 3. Further, the F₃ populations were classified in only two groups as resistant and susceptible then their ratio was 5Resistance/Moderatily Resistance: 3Susceptible.

• All the plant in the F₁ shown resistant reaction with 22.25% disease severity, and in F₂ population the resistant or moderately resistant, and susceptible in the ratio of 3R/MR: 1S.

• The backcross progenies (BC₂F₁) were found similar pattern of tolerant sheath blight as of tolerant parent Tetep.

• The chi-square value of F₂, F₃ and BC₂F₁ showed the non-significant at 5 per cent level of significance indicating that observed data are in accordance with expected ratio and follow mendelian pattern of inheritance to Sheath Blight