Effect of terminal heat stress on genetic responses of biochemical and yield contributing parameters in wheat (Triticum aestivum L.)
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Date
2021
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Department of Plant Breeding and Genetics, BAU, Sabour
Abstract
Heat stress is a matter of a great concern for the wheat crop. Breeding of heat-tolerant cultivars requires knowledge of the genetic behaviour of morpho-physiological traits. Genetic analysis through Generation Mean Analysis helps to find out the nature of gene actions involved in a concerned trait by providing an estimate of main gene effects (additive and dominance) along with their digenic interactions (additive × additive, additive × dominance, and dominance × dominance. Thus, six generations (P1, P2, F1, BC1.1, BC1.2 and F2) of six crosses were sown in timely (normal sown, NS) and late (heat stress, LS) conditions in a Randomized Block Design with three replications in each. Result of scaling test revealed that additive-dominance model is inadequate for explaining the inheritance of most of the studied characters under both environments indicating the presence of non-allelic gene interaction. The traits i.e., Grain filling duration (GFD), canopy temperature (CT), chlorophyll content (CC) and catalase activity (CAT) under heat stress condition was found under the control of additive gene action with dominance x dominance interaction, additive gene action with additive x additive interaction, dominance gene action with additive x additive interaction and dominance gene action with additive x additive and dominance x dominance interaction respectively. Heritability estimates in broad senses were generally moderate to high for most studied characters in six crosses except for grain yield and chlorophyll content. The expected genetic advance from selection estimates in the F2 were high for CT, MSI, CAT, S/MS and 1000GW. Significant genotypic correlation coefficients appeared among grain yield, canopy temperature, relative water content, chlorophyll content and catalase activity under late sown conditions. This suggests useful indirect selection criteria to improve simultaneously these traits, which showed significant heritability along with genetic advance. Moreover, canopy temperature can be considered a significant trait to indicate relative tolerance to terminal heat stress. It can be concluded that the traits investigated showed a complex genetic behaviour, which implies that early selection would be less efficient; therefore, it is recommended delaying the selection to advanced generations to benefit from the reduction of non-fixable genetic variation and exploit transgressive segregants.