Identification of heat tolerant bread wheat (Triticum aestivum L.) genotypes through heat susceptibility index (HSI) and SSR markers

The present study "Identification of heat tolerant bread wheat (Triticum aestivum L.)" genotypes through heat susceptibility index (HSI) and SSR markers" was undertaken by growing 52 genotypes during rabi 2019-20 and rabi 2020-21 in two different sowing conditions (timely sowing and late sowing). Based on pooled results of two years for heat susceptibility index (HSI) and yield stability ratio (YSR), eight genotypes, viz. AKAW 4901, UAS 375, K 1317, WH 1127, HTW 11, WH 1105, HIKK 09 and DBW 14 were identified as heat tolerant genotypes, as these genotypes had heat susceptibility index less than 0.50 and high yield stability ratio (> 83%) with less reduction in grain yield. The screening of all the genotypes was also carried out based on 14 heat tolerant specific SSR markers. Out of the total 14 SSR primers, 6 primers represented the A genome, 4 represented the B genome and the rest of the 4 were from the D genome of wheat. These primers detected 30 polymorphic alleles among the 52 wheat genotypes. The polymorphic information content (PIC) varied greatly between SSR primers and their value varied from 0.20 to 0.49. Cluster analysis using SSR data was determined for each pair of 52 genotypes by Jaccard's similarity coefficient, which revealed that the lowest similarity of 5 per cent was noticed between AKAW 4901 and DBW 246, while the highest of 88 per cent was noticed between DBW 179 and WH 1105 genotypes. Based on the HSI and molecular data analysis 6 genotypes, namely AKAW 4901, UAS 375, K 1317, HTW 11, WH 1105 and HIKK 09 were identified to be heat tolerant and are recommended for cultivation under late sown and rainfed environment. Furthermore, the result of molecular analysis coincides with the result of HSI, and hence in the future only molecular markers can be used to identify the tolerant genotypes rather than going for phenotyping in different environments.