Phenotypic and Molecular Characterization of Adult Plant Resistance to Stripe Rust (Puccinia striiformis f. sp. tritici) in Exotic and Indigenous Wheat Germplasm

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. The frequent breakdown of race-specific, all-stage resistance genes due to the emergence of new virulent pathotypes underscores the need for durable resistance. Adult plant resistance (APR) genes confer partial, largely race-non-specific resistance and provide a sustainable strategy for long-term disease management. In this study, two hundred exotic and indigenous wheat genotypes were evaluated for stripe rust resistance at the seedling stage under controlled glasshouse conditions using five predominant Indian Pst pathotypes (46S119, 110S119, 238S119, 110S84, and 47S103), and at the adult-plant stage in field trials conducted over three consecutive crop seasons (2021–2024). Disease response was assessed using latent period, lesion length, coefficient of infection (CI), final disease severity (FDS), and area under the disease progress curve (AUDPC). Gene-linked SSR markers (csLV34, wmc44, and gwm192) were employed to detect the APR genes Yr18, Yr29, and Yr46, respectively. Field evaluation classified eight genotypes as immune, nine as highly resistant, 22 as resistant, 58 as moderately resistant, 14 as moderately susceptible, 61 as susceptible, and 28 as highly susceptible. Marker analysis identified Yr18, Yr29, and Yr46 individually in 9, 38, and 36 genotypess, respectively, while 20, 10, 51, and 27 genotypes carried the Yr18+Yr29, Yr18+Yr46, Yr29+Yr46, and Yr18+Yr29+Yr46 combinations, respectively; only nine genotypes lacked all three markers. Principal component and correlation analyses revealed that increasing APR gene pyramiding was significantly associated with prolonged latent period and reduced lesion length, CI, and AUDPC, demonstrating additive effects on resistance. Notably, eight genotypes, including BW 35109, BW 35110, BW 35112, BW 35114, BW 35116, and three lines from the 51st ESWYT, carrying two- or three-gene combinations remained immune at both seedling and adult-plant stages across all three years. These genotypes constitute valuable genetic resources for pyramiding durable APR genes and accelerating the development of stripe rust-resistant wheat cultivars.