Deciphering selection criteria for Indian mustard (Brassica juncea L.) encountering high-temperature stress during post-reproductive phase

Abstract

A set of 124 genotypes, which includes released varieties, and diverse fixed lines developed using indigenous and exotic germplasm through various breeding methods, were used to screen for terminal heat stress tolerance. These genotypes along with 5 checks were grown in augmented complete block design in early, timely and late sown conditions. The per cent reductions in mean values of traits recorded in late sown condition in comparison to early sown condition were in decreasing order as: yield per plant (48.6%), thousand seed weight (26.1%), number of primary branches (23.5%), number of siliquae on main shoot (20.8%), and oil (5.9%) whereas, per cent reductions in late sown condition in comparison to timely sown condition were: yield per plant (53.9%), number of siliquae on main shoot (24.3%), thousand seed weight (22.1%), number of seeds per siliqua (12.4%), number of secondary branches (12.4%), siliqua length (11.8%), plant height (6%) and percent oil (3%). Yield per plant was positively and significantly correlated with thousand seed weight (0.39 ** , 0.58 ** ), number of siliquae on main shoot (0.31 ** , 0.24 ** ), and number of primary branches (0.26 ** , 0.18 * ) in timely and late conditions respectively. Number of seeds per siliqua and yield per plant were non-correlated in timely sown (0.06) condition whereas in the late sown condition it showed significant positive association (0.25 * ). Under timely sown condition highest direct effect was exerted by 1000 seed weight (0.40) followed by number of seeds per siliqua (0.27), number of secondary branches (0.26), etc Whereas under late sown condition, thousand seed weight (0.47), number of seeds per siliqua (0.20), plant height (0.18), number of secondary branches (0.12) etc.