Effect of physical mutagen on expression of characters in arid legume pulse cowpea (Vigna unguiculata (L.) Walp.)

Studies on physical induced mutagenesis, gamma rays were performed by exposing the healthy and dry seeds of cowpea variety CO 4 to gamma rays 20, 30, 40, 50, 60 and 70 kR. The study was to evolve economically important mutants with varied seed coat colour as against dark grey coloured seed coat of CO 4. The LD50 value was found at 50kR for 60 Co gamma rays. Under field conditions, germination, seedling survival, plant height on 30th day, pollen fertility, seed fertility, pods per plant, pod length, seeds per pod, 100 seed weight and single plant yield was reduced as compared to the control. In M2 generation, viable macro mutants like dwarf mutant, spreading type, late mutant, semi sterile type, single and tri cotyledonary leaf mutant, basal branching, multiple leaf mutant, white flower mutant, chimeric mutant and seed coat colour mutant were observed. Gamma rays induced higher proportion of chlorophyll mutations. Single type and multiple type mutations occurred more frequently. Economically important macro mutants such as brownish white seed coat colour mutants were observed in M2 generation.