Genetic Analysis of Heat Stress Tolerance in Wheat (Triticum aestivum L.) Using Line x Tester Mating Design

Bread wheat (Triticum aestivum L.) is a critical cereal crop, providing sustenance for over 35% of the global population. Bread wheat possesses remarkable adaptability to diverse climates and soil types. However, heat stress, exacerbated by global climate change, poses a significant threat to wheat production. Developing heat-tolerant wheat varieties is essential to ensuring food security. This study identified to identify genetic variance in heat tolerance through the Line × Tester analysis, a breeding tool that evaluates the combining ability of parental lines. The experimental material comprised 16 crosses derived from four high-yielding lines and four heat-tolerant testers. These were cultivated in Pantnagar, India, under late-sown conditions to replicate heat stress. Agronomic traits such as plant height, tiller number, grains per spike, days to maturity, and grain yield were evaluated. Analysis of variance (ANOVA) was used to estimate general combining ability (GCA) and specific combining ability (SCA), providing insights into additive and non-additive genetic variances. Results indicated significant genetic variability among genotypes, with substantial non-additive genetic components influencing most traits. Plant height, for instance, demonstrated significant GCA and SCA variances, with SCA effects being more pronounced. Similarly, traits like the number of tillers per plant and grains per spike were predominantly controlled by non-additive genetic factors. The study revealed that hybrid combinations significantly influenced growth and yield traits, underscoring the importance of both GCA and SCA in breeding programs. The significant Line × Tester interactions suggest that specific combinations of parental lines and testers are crucial for achieving superior phenotypes. This study supports the notion that both additive and non-additive genetic effects are vital for crop improvement under heat stress, providing a robust foundation for future breeding programs aimed at enhancing wheat resilience to increasing temperatures.