Induced mutations in cowpea

Abstract

Seeds of cowpea ( vigna unguiculata) cultivar kuruthola-payar were subjected to induced mutagenesis using four doses of gamma rays (10 to 40 krad) and four doses of EMS (0.5 to 2.0 per cent) and their effects in the M1 and M2 generations were studied. The germination percentage was observed to decrease prgogressively with the increase in dose of both mutagens although the reduction was more drastic with EMS. Reduction in survival percentage was observed with increase in the dose of gamma rays and EMS. The growth of shoot and root and plant height were reduced by both the mutagens, although gamma rays showed greater shoot inhibition and EMS showed greater root inhibition. The pollen fertility as well as seed fertility decreased linearly with increase in doses of both the mutagens. Chlorophyll chimeras were observed only in the 30 krad and 40 krad gamma ray treatments. Morphological variations noticed included plants with alterations in the number, size and shape of leaflets. The chlorophyll mutation frequency estimated on M2 progeny row basis showed an increase with increasing doses of gamma rays, except in the 40 krad treatment, which showed a slight decrease. In the case of EMS, maximum mutants were observed at the lowest dose. The chlorophyll mutation frequency estimated on M2 seedling basis showed dose-dependence. The frequencies of the different types of chrolophyll mutants did not show any dose-relationship. The segregation ratio of chlrophyll mutants was higher for EMS than gamma irradiation. The viable mutation frequencies did not show any definite relationship with the doses in both the mutagen treatments. The mutagenic effectiveness in inducing chlrophyll mutations was high at the lowest dose of both mutagens. On the basis of lethality, 20 krad of gamma rays was the most efficient, while on the basis of injury and sterility, 10 krad was the most efficient. With EMS, the 0.50 per cent treatment was the most effective as well as the most efficient treatment on the basis of lethality, injury and sterility. The mutagenic efficiency in inducing chlorophyll mutations was higher for gamma rays with respact to lethality and injury, while on the basis of sterility, EMS proved to be more effcient than gamma rays.