Induction of beneficial mutants in rice (Oryza sativa L.)

Abstract

Several popular local rice varieties of Hill Zone of Karnataka grow tall, varieties which lodge under high fertility conditions and harvesting them is cumbersome and calls for extra labour input compared to stiff and erect rice varieties. Gamma irradiation of five popular rice varieties of the zone viz., BKB, Halugidda, Kirwana, PUB and Puttabatta was undertaken at the Regional Research Station, Mudigere for induction and isolation of mutants with non lodging habit. Dry and well filled seeds of the five varieties with 12 per cent moisture were irradiated with gamma radiation dose of 10, 20, 30, 40 and 50 kR and the M1 generation was grown during kharif 1997 using unexposed seeds as control. M2 generation was grown during kharif 1998. Fifty M1 plants without any visible abnormalities were selfed and harvested individually in each treatment and the seeds were sown as plant-to-rows in nursery beds. Frequency and spectrum of chlorophyll mutations in M2 were scored at seedling stage following the classification of Gustafson [1] and frequency of chlorophyll mutations in M2 were estimated as number of mutations per 100 M2 plants as suggested by Gaul [2]. Other viable mutations were scored at or after flowering and mutagenic effectiveness and efficiency were calculated, treatment wise, following Konzak et al. [3].