VYAS, MUKESHMALAV, ASHOK KUMAR2019-07-262019-07-262019Malav, A.K. and Vyas, M.http://krishikosh.egranth.ac.in/handle/1/5810117180Stability Analysis for Grain Yield Component and Heat Tolerance Traits in Bread WheatThe present investigation entitled "Stability Analysis for Grain Yield Component and Heat Tolerance Traits in Bread Wheat [Triticum aestivum (L.) em. Thell]" was conducted during rabi, 2017-18 at the Research Farm Department of Agronomy, Rajasthan College of Agriculture, Udaipur (Rajasthan). The experimental material comprised 8 varieties, their 28 F1’s and two check varieties Raj 4037 and Raj 4079. All genotypes were evaluated in randomized block design with three replications in three different environments i.e. normal sown (E1), late sown (E2) and very late sown (E3). The analysis of variance revealed significant differences between parents and hybrids for all most of the characters in all the three environments. Significant differences among parents and hybrids for the concern characters suggested presence of considerable amount of genetic variation in the materials. The pooled analysis of variance revealed significant differences between genotypes, parents and hybrids were also significant for all the characters, indicating that between genotypes, between parents and between hybrids difference was significant and average heterosis was there. G x E interactions were significant for proline content, chlorophyll content, chlorophyll stability index and heat injury, indicating influence of different environments on the expression of genotypes. Among the crosses PBW 343 x Raj 4238, Raj 3765 x Raj 4238, GW 173 x Raj 4238, HI 1544 x GW 366 and PBW 343 x GW 366 were showed significant economic heterosis in all the environments and pool, indicating their utility for different environments. Among these, most of the crosses also exhibited significant economic heterosis for one or more components and heat tolerant characters. The analysis of variance for combining ability indicated significant difference for GCA and SCA for all most of the characters in all the three environments suggested difference between parents for GCA and between hybrids for SCA. Over the environment mean square due to GCA x E and SCA x E were significant for proline content, chlorophyll content, chlorophyll stability index and heat injury. * Ph.D. Research Scholar, Department of Genetics and Plant Breeding, Rajasthan College of Agriculture, Udaipur-313001 ** Major Advisor, Professor, Department of Genetics and Plant Breeding, Rajasthan College of Agriculture, Udaipur-313001 The estimates of general combining ability effects indicated that parents Raj 4238 and HI 1544 were good general combiners for grain yield per plant and most of components along with heat tolerance characters and can be used for further breeding programme. The crosses PBW 343 x Raj 4238, Raj 3765 x Raj 4238, GW 173 x Raj 4238, HI 1544 x GW 366, PBW 343 x GW 366, Raj 3765 x DBW 17 and Raj 4120 x DBW 17 in all the three environments and pool, depicted high economic heterosis along with at least one good general combiner parent and high SCA effects in pool. These crosses may be exploited through identifying transgressive segregants in segregating generations. The pooled analysis of variance for stability revealed that genotypes were found to be highly significant for all the characters studied when tested against pooled error as well as pooled deviation indicating significant difference among them. Parents Raj 4120, GW 366 and DBW 17 had regression coefficient around unity (bi=1) with high mean value than population mean, indicated its suitability and stability of performance under varied environments. The parents RAJ 4238 showed high mean with regression coefficient value less than unity (bi<1) indicated adaptability to unfavorable environments. Overall study on yield, yield contributing and physiological characters, it was observed that five stable hybrids viz., PBW 343 x RAJ 4238, Raj 3765 x Raj 4238, GW 173 x Raj 4238, HI 1544 x GW 366 and PBW 343 x GW 366 resulted that the hybrids found stable for grain yield per plant also depicted stability in respect of its one or more yield component traits like days to maturity, plant height, number of effective tillers per plant, emergence of flag leaf, spike length, number of spikelets per main spike, length of awns, number of grains per spike, flag leaf area, test weight, biological yield per plant, grain yield per plant, heat injury, leaf canopy temperature, proline content and chlorophyll stability index, indicated that the stability of various component traits might be responsible for the observed stability of different hybrids for grain yield per plant. In order to determine relative tolerance, the heat susceptibility index was estimated for grain yield per plant. An overall appraisal revealed the crosses GW 173 x GW 366, HI 1544 x GW 366, HI 1544 x GW 173, GW 173 x Raj 4238, HI 1544 x DBW 17 and Raj 3765 x PBW 343 for grain yield per plant were least affected under late sown conditions. High grain yield of a genotype under late sown condition indicated the presence of genes for heat tolerance.ennullThesis