Morpho-physiological Characterization of Bread Wheat Accessions for Heat Stress Tolerance under Late Sown Conditions of North-Western Plain Zone of India

Abstract

Bread wheat is grown in the sub - tropical and tropical regions world - wide. Terminal - heat stress is a major abiotic stress in wheat and global warming due to climate change has negatively impacted its production and productivity. We evaluated 96 accessions of bread wheat germplasm, which included 79 indigenous and 17 exotic collections, by investigating 16 morpho - physiological and yield - related traits during two successive Rabi seasons of 2018 - 19 and 2019 - 20 under non - stressed and heat - stressed (as a delayed sown crop) environments. Heat susceptibility index (HSI) was used to classify tolerant (HSI <1.0) and susceptible (HSI >1.0) accessions. The heat - stress showed negative impact on the phenotypic expression of 14 morpho - physiological and yield related traits by reducing the traits more prominently in susceptible accessions than the tolerant. However, early ground cover showed the increased expression in the tolerant accessions and higher variability in the germplasm under the heat - stress. Grain length / width ratio (LWR) also improved in the germplasm under heat - stress, while, there was a marked increase in LWR of the susceptible accessions mainly due to relatively higher decrease of grain width in these accessions under heat - stress. The plot yield associated positively with its contributing traits namely yield per plant, number of grains per plant, number of grains per spike, grain weight per spike and plant biomass under both the non - stressed and the heat - stressed environments, but its association with chlorophyll fl uorescence was only under heat - stress. The germplasm accessions IC574476 (HD2967), IC393878 (WH157), IC296383 (WR544), EC534487 (PAU351), IC519900 (HD2932) and IC539221 [EIGN - I - (04 - 05) / 149] produced high yield and were stable across the environments. The identifi ed bread wheat germplasm lines could be used as potential parents for bi - parental and multi - parental populations.