Assessing alpha lattice design for heat stress indices and yield stability in wheat genotypes.

Wheat (Triticum aestivum L.) faces increased susceptibility to terminal heat stress, a major yield-limiting factor, especially in subtropical regions. Despite India's anticipated record wheat production for 2024-25, high temperatures during the grain-filling stage threaten yield stability. This study assessed the relative efficiency of the alpha lattice design (ALD) against the randomized complete block design (RCBD) in quantifying fifteen heat stress indices (HIs) among 200 recombinant inbred lines (RILs) derived from WH711 × WH1021. The experiment was conducted at Chaudhary Charan Singh Haryana Agricultural University, during 2018-19 Rabi season over two sowing dates, capturing diverse environmental conditions. Results showed tolerance and yield stability indices with the largest (-56 to 614) and smallest (0.30 to 1.09) ranges, respectively, and most HIs exhibited medium to high heritability. Complementary gene interactions were noted for stress tolerance, yield index, yield stability, relative heat, and heat resistance indices, while duplicate gene interactions were observed for heat susceptibility index. Significant genetic variability among RILs was observed, identifying RILs 34, 59, and 106 as the most heat-tolerant with superior yield and stability. The ALD improves precision, achieving lower error mean squares and reduced coefficients of variation compared to RCBD, with a relative efficiency (RE) range up to 1.05. These findings underscore ALD's value in managing environmental heterogeneity in trials with large genotype sets and advancing genetic precision under stress, supporting its use in breeding programs focused on developing heat-resilient wheat cultivars amidst rising climatic challenges.