Deciphering Genotype-by-Environment Interaction to Identify Target Test Environments and Stable Stripe Rust-Resistant Wheat Genotypes

Abstract Climate change necessitates innovative approaches to account for environmental effects in future wheat breeding programs aimed at managing stripe rust. The most effective and environmentally friendly strategy for managing stripe rust is the incorporation of resistance genes into the background of elite cultivars. In this multi-environment evaluation, the GGE biplot approach was used to identify genotypes with stable resistance against stripe rust. A total of 441 germplasm entries were initially tested for their seedling responses against the most prevalent pathotypes of Puccinia striiformis f. sp. tritici ( Pst ) (viz., 238S119, 110S119, and 46S119). Based on infection-type data, 30 lines were highly resistant to all three pathotypes, while 27 were highly susceptible. Field responses were evaluated based on final rust severity (FRS) and the area under the disease progress curve (AUDPC) observed over a period of three years at Ludhiana and Gurdaspur. The lines were categorized as highly resistant, resistant, moderately resistant, moderately susceptible, or susceptible. GGE biplot analysis revealed inconsistency in genotype performance across environments. The first two principal components explained 93.2% of the total variation (87.87% and 5.33% by PC1 and PC2, respectively). IC111939 (G1) was identified as the “ideal” genotype, with a small projection from the average environment coordination (AEC) abscissa and a moderate resistance response to stripe rust. Ludhiana (2019-20) and Gurdaspur (2018-19) had small angles with the AEC abscissa, indicating a positive association, with Ludhiana showing the highest “desirability index” and serving as an “ideal” test site for screening rust resistance. Environmental effects were analysed using step-wise regression, revealing that maximum temperature, relative humidity, location, and the years 2019 and 2020 had positive effects, while 2021 had a negative effect on disease severity.