Mukti Ram Poudel*, Suryakant Ghimire, Madhav Prasad Pandey, Krishna Hari Dhakal, Dhruba Bahadur Thapa, Hema Kumari Poudel

The field research was conducted at the Bhairahawa, Nepal in 2016/17 and 2017/18 in order to determine the physio-morphological and yield potential traits associated with heat and drought tolerance in wheat genotypes. The plant material consists of 20 genotypes out of which 17 were advanced lines and 3 were commercial varieties of Nepal. The research was carried out in alpha lattice design with two replications under three different environmental condition i.e. fully-irrigated, late sown and drought condition. In each replication there were 5 blocks consisting of 4 plots. Each plot was 4 m in length and 2.5 m in width. Each plot consists of 10 rows with a spacing of 25 cm between the rows and there was continuous sowing in a row. Seed sowing on Irrigated and Drought condition was done in 23^{rd} November 2016 and 2017, similarly, seed sowing on Heat stress environment was done on 28^{th} December 2016 and 2017. Data recoding were done for days to heading, days to maturity, plant height, grain yield, spikes/m^{2}, number of grains per spike, thousand grain weights. The mean values of all yield potential traits in Heat stress and drought condition were less than in irrigated condition. Genotypes were significantly different for all phenological traits in irrigated heat stress and drought treatments. The mean number of days to heading for irrigated, drought and heat stress condition was 78.22, 76.58 and 60.8 respectively. The mean number of days to maturity for irrigated, drought and heat stress condition was 115.3, 110.41 and 99.25 respectively with the mean of 108 days. Similarly, mean plant height for irrigated, drought and heat stress condition was 89.53, 68.21 and 79.9 cm respectively with the mean of 81 cm. The mean spike/m^{2} for irrigated, drought and heat stress condition was 340.025, 226.11 and 262.73 respectively with the mean of 276.28. Similarly, the mean NGPS for irrigated, drought and heat stress condition was 43.32, 36.68 and 37 respectively with the mean of 39. The mean TKW for irrigated, drought and heat stress condition was 45.06,40.25 and 36.025 g respectively with the mean 40.445 g. It was observed significant difference in genotypes and environments for yield and yield potential traits. Genotype by environment interaction showed significant difference for grain yield. The mean grain yield for irrigated, drought and heat stress condition was 3.3, 1.4 and 1.79 ton/ha respectively with the mean of 2.18 ton/ha. Under normal irrigated condition, BL4708 highest mean yield with 3731.5 kg/ha and NL1328 yield lowest mean yield of 2.65 ton/ha. In heat stress condition BL4699 had maximum mean yield of 2.22 ton/ ha and NL1307 had minimum mean yield of 1.18 ton/ha. Similarly, in drought condition NL1327 had maximum mean yield of 2.0 ton/ha and NL1325 had minimum yield of 1.04 ton/ha.