Trends in Biosciences

Rice (Oryza sativa) is one of the most important staple food grain crops in the world, forms the staple diet of 2.7 billion people. Khush and Brar (2002),reported that rice provides 32–59% of the dietary energy and 25–44% of the dietary protein in 39 countries. Sheath blight is considered tobe an important disease and caused by fungus Rhizoctoniasolani Kuhn [Teleomorph: Thanatephorus cucumeris (Frank) Donk], causes extensive losses to rice crop varying from 8 to 50% (Savaryet al., 2000). 201 mutated genotypes of Pusa Basmati-1 (M₄ generation) rice variety ware inoculated by Rhizoctoniasolani. After 96 hrs of inoculation, the number of lesions that appeared on the rice sheath were variable in different genotypes. Data of lesion length was taken at 7^th, 14^th and 21^st days after inoculation and analyzed using the AUDPC (Area Under Disease Progress Curve) value (Chand, et al., 2006). The AUDPC values among mutated rice genotypes ranged between 28 to 184 whereas in control (untreated) it was 170. The significant variation was observed in the AUDPC value in mutated population as compared to the control. AUDPC range of genotypes from 28 to 93 (110 plants), 93 to 158 (83 plants), 158 to 184 (8 plants) considered resistance, susceptible, highly susceptible plants, respectively. The mutants of AUDPC range from 28 to 93 (110 plants) group have been selected for advancement to generation. These genotypes could be considered a M₅ potential source for disease resistance against the sheath blight of rice and can be utilized in breeding programmes for development of sheath blight resistant rice.