Molecular Plant Breeding 2025, Vol.16, No.1, 82-92 http://genbreedpublisher.com/index.php/mpb 88 with specific haplotypes (Hap-20 and Hap-21) showing strong heat tolerance (Table 1). These findings highlight the success of breeding heat-tolerant wheat varieties, enabling wheat to maintain a stable yield under high temperature stress conditions. Table 1 Variation in seedling traits among 24 haplotypes of the wheat TaHST1 QTL under heat stress (HS) conditions (Adapted from Khan et al., 2022a) Haploty pe Xhau-1 Xhau-2 Xhau-3 Xhau-4 Xhau-5 Deleted sites Number of lines Frequency (%) RL (cm) in HS RW (g) in HS SL (cm) in HS SW(g) inHS Hap1 − − + 127 − 3 34 19.4 14.3 0.14 36.4 0.8 Hap2 − − − − − 5 23 13.1 14.3 0.11 37.4 0.78 Hap3 − − + 127 + 2 20 11.4 13.7 0.1 37.6 0.84 Hap4 − − − 195 − 4 17 9.7 14.1 0.12 38.8 0.75 Hap5 + + + 127 + 0 16 9.1 15 0.15 37.3 0.83 Hap6 − − − 127 + 3 11 6.3 15.3 0.17 38 0.83 Hap7 − − − 127 − 4 9 5.1 9.4 0.09 35.3 0.87 Hap8 − − − 127 − 4 9 5.1 13.6 0.09 37 0.72 Hap9 + − + 127 + 1 8 4.6 12.8 0.09 36.4 0.73 Hap10 + + + 127 − 1 7 4 15 0.13 41.1 0.85 Hap11 − + + 127 − 2 5 2.9 13.8 0.13 35 0.67 Hap12 − − − 195 + 3 5 2.9 15 0.11 36 0.82 Hap13 − − + − − 4 4 2.3 13.2 0.07 37.2 0.73 Hap14 − − − − + 4 3 1.7 12.7 0.07 31.2 0.66 Hap15 + + + − + 1 3 1.7 15.6 0.17 39.7 0.82 Hap16 + + − 127 − 2 2 1.1 14.7 0.13 35.6 0.71 Hap17 − + − − − 4 1 0.6 20.2 0.17 40 0.88 Hap18 + + + − − 2 1 0.6 14.3 0.26 42 0.59 Hap19 + − + − + 2 1 0.6 13.2 0.14 43 0.76 Hap20 + + + 195 + 0 1 0.6 14 0.11 40.6 1.03 Hap21 − + − 127 − 3 1 0.6 14 0.22 41.3 1 Hap22 − + − 127 + 2 1 0.6 13.4 0.07 32 0.7 Hap23 − − + 195 − 3 1 0.6 12.5 0.09 36.3 0.7 Hap24 − − + 195 + 2 1 0.6 14.3 0.07 36 0.8 Total 175 100 Note: + and − shows positive and negative amplifications; Xhau-4 is a co-dominant marker showing amplifications of 127 bp or 195 bp depending on the genotype; RL: root lenght; RW: root wenght; SL: shoot lenght; SW: shoot wenght 7.2 Performance of heat-tolerant wheat varieties in different regions The performance of heat-tolerant wheat varieties has been evaluated across various regions, demonstrating their adaptability to different climatic conditions. For example, the research by Gourdji et al. (2013) utilized data from 25 years of wheat trials in 76 countries to assess genetic gains in heat tolerance. The study found that the Semi-Arid Wheat Yield Trial (SAWYT) showed the strongest genetic gains at the hottest temperatures, indicating the effectiveness of targeted breeding efforts in hot environments. Similarly, Fu et al. (2023) evaluated 304 elite winter wheat lines from the US, Australia, and Serbia, identifying significant genetic variation for chlorophyll retention and seed weight under heat stress. The study proposed two mechanisms of heat tolerance during grain filling, represented by wheat lines OK05723W and TX04M410164, which could be useful for breeding programs. These case studies highlight the successful application and performance of heat-tolerant wheat varieties in diverse regions, contributing to global food security. 7.3 Implementation experiences in heat-tolerant wheat breeding programs Practical strategies and operations in heat-tolerant wheat breeding programs have been crucial in achieving success. The study by Langridge and Reynolds, (2021) emphasized the importance of combining genetic analysis,
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