Identifying stable parental lines for stripe rust resistance in soft red winter wheat

Abstract Stripe rust, caused by Puccinia striiformis f. sp. tritici, continues to be a major challenge in soft red winter wheat (SRWW) production, especially in the southern United States. In this area, mild winters and wet springs frequently lead to early and severe disease outbreaks. Although many lines demonstrate resistance in a single season, that resistance often does not last across multiple years. For breeding programs, this variability makes it hard to identify truly reliable lines. In this study, we evaluated 111 SRWW breeding lines over three consecutive growing seasons (2021–2024) under artificial inoculation in field conditions in Fayetteville, Arkansas. Stripe rust severity was rated on a 0–4 categorical scale, and data were analyzed using linear mixed models (LMM) and generalized estimating equations (GEE). The initial estimate of broad-sense heritability was 0.73. However, a refined LMM that included variance components across all seasons provided a more conservative estimate of 0.57, still indicating significant genetic influence. Despite yearly differences in disease pressure, genotype rankings stayed relatively consistent. Several lines consistently showed low disease severity across years, while susceptible checks confirmed uniform inoculum distribution. These observations suggest limited genotype-by-environment interaction and strong genetic effects. Our results highlight the importance of multi-year field evaluation. The stable resistant lines identified here provide valuable options such as parental material or reliable checks, aiding in the development of SRWW cultivars with durable stripe rust resistance.