Genetic Analysis of Heat Tolerance in Upland Cotton Gossypium Hirsutum L

Abstract

About 204 genotypes consisting of germplasm and advance breeding lines were newlinescreened under three environments for heat tolerance during Kharif at two environments newlineand summer at one location. Magnitude of genetic variability revealed high PCV and newlineGCV for seed cotton yield and its related traits, similarly, leaf area at 90 and 120 DAS newlineamong physiological traits recorded high estimates of PCV and GCV, while among newlinefibre quality traits, micronaire and fibre maturity coefficient recorded moderate PCV newlineand GCV under both Kharif-rainfed (Dharwad) and Kharif-irrigated (Raichur) newlinetemperature regimes. Genotypes exhibited high to moderate PCV and GCV for morphophysiological newlinetraits under summer environment, none of the genotypes could produce newlineharvestable seed cotton and few genotypes maintained a healthy green foliage which newlinewere identified as vegetative heat tolerant lines. newlineCharacter association studies across the two Kharif temperature regimes newlineindicated that seed cotton yield per plant expressed significant positive correlation with newlineboll retention, boll number, boll weight. While, the canopy temperature at peak newlineflowering and boll development stage was significantly associated in negative direction newlinewith seed cotton yield. Hence, canopy temperature, boll retention, boll number and boll newlineweight are the important traits which needs to be considered for improving heat newlinetolerance. newlineLine × Tester analysis evaluation involving 120 hybrids and their parents at two newlinetemperature regimes during summer 2018 at MARS, Dharwad indicated higher newlinemagnitude of SCA variances than GCA variances for all the 34 traits in both early sown newlineand late sown temperature regimes. The magnitude of heterosis for seed cotton yield, newlinephysiological and fibre quality traits was considerably high for the hybrids at both early newlinesown and late sown conditions. Three hybrids viz., PH-93 × CPD-1501, EC560323 × newlineEC137592 (Tanaroon-2-78) and RAHC-1017 × PRS-74 were identified as promising newlineheat tolerant hybrids, based on their heat tolerance index values.