Genetic dissection of physiological traits over trait based breeding in bread wheat conferring terminal heat tolerance

Abstract

Breeding of heat-tolerant cultivars requires knowledge of the genetic behavior of morpho-physiological traits. Gene action was investigated using wide phenotypic segregation ranging across six generations (P1, P2, F1, BC1, BC2 and F2) of four different tolerant×sensitive crosses for grain flling duration, GFD (40.14–46.20); canopy temperature depression, CTD (2.42– 5.97); normalized diference vegetation index, NDVI (0.35–0.61); membrane thermostability index, MSI (31.40–40.93); no. of grains/spike, GN/SP (26.29–54.80); thousand-grain weight, TGW (31.70–44.45); and grain yield/plant, GY (15.37–24.89) under terminal heat stress. Scaling results indicated an absence of epistasis for MSI and TGW in cross PBN51×HUW510. The prominence of Dominance×dominance interaction over additive×additive and additive×dominance interactions along with signifcant dominant gene efect [h] for all traits except MSI was observed. For MSI, similar signs of [d] and [i] along with signifcant [j] showed the possibility of exploitation of additive gene efect. CTD, NDVI and GN/SP were controlled by duplicated epistasis, whereas both complementary and duplicate epistasis was found for GFD. Digenic interactions with prominent duplicate epistasis indicate that biparental mating or diallel selective mating might be efciently utilized for their improvement. The present investigation indicated a preponderance of non-additive gene action for studied traits, thus, implying toward delaying of selection to the later generations to exploit transgressive segregants. Any conventional breeding strategy would be followed for generating the cultivars with low CTD, reduced cell membrane injury, with higher NDVI, TGW, GFD, no. of grains/spike and grain yield/plant.