Singh, Y.V.Negi, Tribhuwan Singh2019-01-302019-01-302018-06http://krishikosh.egranth.ac.in/handle/1/5810092896The present investigation was conducted to induce genetic variability in six cowpea cultivars viz. PL-1, PL-2, PL-3, PL-4, PL-5 and PGCP-28 and to isolate leaf thrips resistant mutants which can be used as such as new varieties or as parents in hybridization programme for developing superior varieties. The seeds of the six cowpea varieties were exposed to 25 kR (250 Gy) doses of Co 60 gamma radiations at Bhabha Atomic Research Centre, Trombay, Mumbai. The experiment was undertaken during kharif Season, 2016, zaid season, 2017, kharif season, 2017 and zaid season, 2018 at Breeder Seed Production Centre (BSPC), Govind Ballabh Pant University of Agriculture & Technology, Pantnagar, Udham Singh Nagar, Uttarakhand. The effect of gamma rays treatment on the per cent seed germination was studied in M1 generation and results indicated that the gamma rays had an inhibitory effect on the per cent seed germination of cowpea. In M2 generation, the plants were screened for desirable traits like tallness/dwarfness, earliness, pod per plant and leaf thrips resistance. In PGCP-28, 47 resistant and 112 moderately resistant plants were identified accounting for 6.41% and 15.27% of mutation respectively. The seed mutants were also isolated having black, dark brown and dark red seed coat colour. In M3 generation, various desirable mutants for yield traits were isolated having high number of pods per plant ranging from 57 to 65. Pod mutants having curved and upright pods and black seed coat mutants were also observed in M3 generation. During M4 generation, leaf thrips resistant and moderately resistant mutant were identified in PL-5 and PGCP-28. The numbers of leaf thrips resistant mutant in PL-5 and PGCP-28 was 68 and 28 respectively. Various other mutants like sterile and partial sterile mutants were also observed from M1 to M3 generation having sterile and partial sterile pollens. Thus, there was increase in the variability for different characters. Several desirable mutants were isolated having early maturity, vigorous plants growth, long pod length, high number of pods per plant and resistant to leaf thrips which can be exploited in cowpea improvement programme especially breeding for leaf thrips resistance. Mutant having upright pods with long peduncle can be advanced to develop plant types that are suitable for mechanical harvesting. Thus, mutation breeding can be effectively used for cowpea improvement particularly breeding for biotic stresses.ennullThesis