Title: Effect of preirradiation colchicine treatment on mutation spectrum of Phaseolus aureus Roxb.
Abstract: Effect of gamma-rays on 1) dry seeds 2) seeds presoaked for 3 hours in distilled water and 3) seeds pretreated with 0.2%colchicine for 1 hour were studied. Germination was adversely affected in presoaked seeds. Almost all the germinated seedling survived. In M2 fringed leaf mutant, strap leaf mutant, advanced stigma mutant, trisomic and male steriles were isolated. Results of genetical analysis revealed monogenic recessive nature of first two mutants. Possible pleiotropic or close likage nature of mutants has been discussed. The trisomic displayed reduced vigour and high pollen sterility, which is influenced by environmental factors. Temperature sensitivity of male steriles has also been discussed. The advanced stigma mutant changes the breeding system from inbreeder to outbreeder. Its utility in hybridization programme is obvious. As all these mutations were isolated in precolchicinized irradiated seeds the importance of colchicine treatment in combination with gammarays resulting in increased spectrum of mutations has been discussed.