Characterization of Bread Wheat Genotypes Using SSR Markers for Terminal Heat Tolerance

Wheat is a major global food crop, but its productivity is increasingly threatened by terminal heat stress due to climate change. This study aimed to characterize the genetic diversity and heat tolerance of widely grown bread wheat genotypes using SSR markers to identify heat-tolerant cultivars adaptable to various regions in Bangladesh. A total of 15 genotypes were screened, and 13 polymorphic SSR (Simple Sequence Repeats) markers were used to determine the genetic similarity and categorize genotypes based on their heat tolerance. The molecular analysis revealed 13 polymorphic SSR markers that produced distinct PCR (Polymerase Chain Reaction) bands across the different genotypes. By the conclusion of the study, bread wheat genotypes were categorized as either tolerant or sensitive to heat, and the genetic similarity among the varieties was assessed using molecular markers. The genetic similarity coefficients obtained from the SSR primer screening ranged from 0.00 to 0.925. The lowest genetic distance (0.000) was found in Nadi 2 vs BAW1147 variety pair indicating that they are genetically similar to each other. Comparatively higher genetic distance (0. 925) was observed between BAW 1290 vs BARI Gom 28. The dendrogram divided the fifteen genotypes into two main groups, A and B, both formed at a similar coefficient of 0.05. Group A included seven genotypes and was further divided into two clusters, while Group B comprised eight genotypes, which were also divided into two clusters. The categorization of the genotypes was based on the average Heat Susceptibility Index (HSI), Thousand Grain Weight (TGW), grain yield, and the relative reduction in TGW and grain yield under stress conditions compared to timely sown conditions, aligning with the molecular data. Among the fifteen genotypes, BARI Gom 25, BARI Gom 26, BARI Gom 27, BARI Gom 28, BARI Gom 29, BARI Gom 30, and BARI Gom 31 demonstrated their adaptability to late sown conditions. The heat tolerance observed in these genotypes, as indicated by their SSR marker scores, is anticipated to provide valuable insights for molecular breeding studies focused on heat resistance.