Harnessing Heat Susceptibility Index to Screen Bread Wheat Genotypes for Heat Tolerance

Wheat (Triticum aestivum L.) is one of the most widely cultivated cereal crops globally and is highly susceptible to heat stress, especially during reproductive phase, which adversely impacts grain yield. Screening and evaluation of diverse genotypes using the heat susceptibility index (HSI) is one of the effective methods that enable identification of heat-resilient lines for breeding programs. HSI values were estimated for 45 genotypes including 8 lines, 4 testers, their 32 hybrids and one check for grain yield per plant and other major contributing traits such as biological yield per plant, grain filling period, chlorophyll content at 15 days after anthesis and chlorophyll content at 21 days after anthesis. Results revealed that among 45 genotypes, 14 genotypes namely AKAW 5104 x DBW 110, MACS 6768, GW 547 x MP 3288, AKAW 5104 x GW 11, DBW 359 x MP 3288, MP 3557 x MP 3288, GW 547, LOK 1, GW 547 x DBW 110, HI 1669 x LOK 1, Check (GW 513), HI 1669 x DBW 110, GW 11 and AKAW 5104 had HSI<0.75 for grain yield per plant and related traits. Hence, these genotypes were considered as heat tolerant and on further evaluation for heterosis and combining ability, these genotypes likely provide an opportunity to develop high yielding heat tolerant wheat varieties.