Changes in Serbian Yellow Rust Races Reveal Genotype-Specific Responses of Yield and Quality-Related Traits in...

Wheat yellow (stripe) rust (Puccinia striiformis f. sp. tritici) remains a major constraint to wheat production, yet relationships between infection level, yield, and quality-related traits are often inconsistent. This study evaluated how contrasting yellow rust races and infection intensities influence yield, test weight (TW), thousand kernel weight (TKW), and crude protein content in commercial winter wheat varieties. Field trials were conducted in 2016, 2021, and 2023, representing seasons that differed in yellow rust incidence and severity. The yellow rust race was changed in 2023 compared to the yellow rust race that was the same in 2016 and 2021. Associations between qualitative variables (variety and year) and quantitative variables (yield, TKW, TW, disease index (DI), and protein content) were analyzed using principal component analysis for mixed data and regression modeling. At low to moderate infection levels, TW showed a stronger negative linear association with yellow rust DI than TKW, suggesting that TW acts as an early indicator of source limitation. In contrast, TKW declined only when genotypes could no longer compensate for reduced assimilate supply, after which both traits responded similarly under severe physiological stress. Protein concentration increased under high infection levels, but its association with yield loss and DI was weak. Under high disease pressure, yield and quality-related responses were highly variable and genotype-specific at comparable DI levels, demonstrating that equivalent symptom expression does not necessarily translate into equivalent physiological disruption. These results show that yield and quality responses to yellow rust cannot be inferred from DI alone, highlighting the importance of physiological tolerance and source-sink efficiency in breeding and disease management strategies.