General Combining Ability and Specific Combining Ability Analysis for Terminal Heat Tolerance in Wheat (Triticum Aestivum L.)

Abstract

Developing bread wheat genotypes for terminal heat tolerance is a critical objective for future breeding approaches. The line x tester mating analysis is one of the best approaches to demonstrate the appropriateness of the bread wheat genotypes for selection programs. For this purpose, nine genotypes viz.  T.J-83, NIA Sarrang,  Khirman, SKD-1, Sehar-2006, Sarsabaz, AS-2002, NIA-Amber, and Nifa Barsat were used in this research. The experiment was planned in a factorial design with two treatments (normal and heat stress) at  Botanical Garden  Farm,  Sindh Agriculture University Tandojam, during 2019-2020. The results depicted that at terminal heat stress, the genotypes were significantly affected by yield and physiological traits at late sowing. During the initial screening, the female parents, T.J-83, Sarsabaz, and Nifa Barsat executed very well under heat stress conditions for nearly all the yield and morphological traits. Similarly,the male parents such as Khirman and SKD-1 also performed well under heat stress conditions for all traits compare to the female parents. Furthermore, through genetic analysis, the mean effects of General Combining Ability  (GCA)  and Specific Combining Ability (SCA) were significant for all the characters signifying that additive and non-additive variances are important. Further, in heat-stress environments, the GCA was dominant for most characters in contrast to SCA variations. Hence, in this study, under both normal and heat stress conditions, Khirman and SKD-1 proved to be better general combiners for various characters. Therefore, these genotypes are recommended as vigor parents for hybridization and selection programs as emerging terminal heat stress tolerant genotypes.