Response of some faba bean genotypes to heat stress under environmental variations

The faba bean productivity is affected by high temperatures during the growing season. Therefore, faba bean genotypes must be developed to tolerate heat stress. In this study, nine genotypes were assessed over two years and two locations under normal and heat-stress conditions to identify high-yielding, and heat-tolerant genotypes. Seed and straw yields, along with most of the traits under study, showed high genotype diversity and genetic variability across years and locations under in both conditions, according to the combined ANOVA. Seed yield and other traits under investigation were significantly reduced by heat stress, yielding values lower than under normal conditions. When comparing the two years and two locations, the 2023/2024 growth year and the El-Minya location under both conditions had the best values for the majority of the attributes under study. Nubaria 3, Giza 843, and Giza 429 genotypes showed the capacity to produce earlier and increase seed yield/plant, and were among the most investigated attributes under heat-stress conditions, according to the mean performance. MP, GMP, STI, and HM stress indices were associated with both normal and heat-stress conditions; thus, they were more effective at identifying high-yielding genotypes. The genotypes Giza 843, Nubaria 3, and Giza 429 exhibit heat tolerance as indicated by stress tolerance indices. A strong positive correlation was found among SY/P, BY/P, NP/P, and SP traits, as well as among other studied traits in both conditions. The PCs biplot effectively separated genotypes associated with higher seed yield and related traits from those associated with lower grain yield and related traits. These traits, based on univariate and multivariate models, can be used for direct selection to increase faba bean productivity under heat stress. According to statistical analyses, the Nubaria 3, Giza 843, and Giza 429 genotypes have significant potential under heat-stress conditions. Therefore, they could serve as a source of short-duration cultivars to enhance seed and straw yields in the Egyptian faba bean breeding program in the future.