Evaluation of Cimmyt’s Biofortified Elite Wheat (Triticum Aestivum L.) Genotypes for Heat Stress at Different Reproductive Stages

Wheat ( Triticum aestivum L.) is a global cereal crop and a primary food source, but its yield and nutritional value of the grain is getting vulnerable to changing climate patterns especially heat stress during reproductive development. The present study was designed to screen forty nine elite wheat genotypes from CIMMYT's 13th High Zinc Wheat Trial (13th HZWYT) alongside a local check (Akbar-19) for agro-morphological traits, disease resistance, yield parameters and grain Zn and Fe concentrations under normal field conditions during 2022–23, followed by targeted heat stress evaluation at anthesis (T1) and grain filling (T2) stages using polythene tunnels during 2023–24. For all the traits evaluated, highly significant genotypic variation (P ≤ 0.001) was observed during both the cropping seasons. Resistance to moderately resistant responses against yellow and stem rust were observed for the majority of CIMMYT genotypes, with Akbar-19 being highly susceptible. Ten superior genotypes along with check out of fifty were selected based on principal component analysis and Pearson correlation for heat stress study. Heat stress significantly reduced spike length, spikelets per spike, thousand grain weight, and grain yield per plant, with anthesis-stage stress causing greater yield reductions than grain filling stress. The Zn concentration in grain increased in a progressive manner during both stress treatments, whereas the Fe concentration decreased during the heat stress at grain filling stage indicating differential heat sensitivity of the micronutrient loading pathway. Regression analysis between control and stress environments revealed that grain Fe and Zn were the most genotypically stable traits, while TGW showed the greatest stress timing-dependent rank instability. Genotypes G-445, G-439, G-434, G-419, G-443 and G-405 were high yielding with high micronutrient concentrations and were consistently found to be heat stress resistant in both anthesis and grain-filling stages. These findings provide a reliable basis for selection of genotypes for further screening, genotyping, and multi-location testing in heat-resilient wheat biofortification breeding programs.