Title: Performance and stability of nepalese wheat genotypes under irrigated, drought and heat stress environments and genetic diversity of wheat genotypes by using stress tolerance linked marker
Wheat is a major cereal crop important for human nutrition and plays a vital role in food security of Nepal. Present study aimed at identifying high yielding, drought and heat adapted wheat lines and understanding the variation of yield attributing characters under the rising temperature and frequent droughts under changing climate. The twenty elite wheat lines and check varieties were evaluated in alpha-lattice design with two replications under irrigated, heat stress and drought condition during 2016-2017 and 2017-2018 wheat seasons. The wheat genotypes varied significantly among themselves for all the characters studied under irrigated, drought, and heat stressed environments individually and pooled analysis over the environments. The genotype x environment interaction analysis with AMMI model revealed genotype responded differently to the stress environments and stability analyses with AMMI and GGE biplot methods identified genotypes adapted to specific environment and stable across the three test environments. Based on comparison to irrigated optimum, heat stress advanced heading by 22 and 1% days whereas drought maturity by 14 and 4% days. Drought stress was found to be was more severe on yield than heat stress with 57 and 46 % reduction in grain yield respectively. Heat stress had higher effect on days to heading, days to maturity and 1000-grain weight whereas, drought had greater effect on yield, plant height and spike/m2. Drought and heat stress had similar effect on number of grains/spike. Under irrigated optimum condition, BL4708 had the highest mean yield, whereas NL1325 was the most stable genotype adapted to this environment. Under heat stress, BL4699 was the highest yielder and NL 1326 was the most stable genotype. Similarly, in drought condition NL1327 had highest mean yield whereas, NL1244 was the most stable genotype. NL1202 and NL1253 were the most stable genotypes across the three test environments over years, at par with the check varieties Bhrikuti and Gautam. The genotypes adapted to specific stress environments and stable across the environments mentioned above can be further evaluated and promoted as candidate varieties. The drought and heat stress tolerance linked SSR were polymorphic on the studied genotypes and cluster analysis showed distinct groups with some relevance to stress adaptation.