Development and application of a Puccinia triticina avirulence gene AvrLr15-specific molecular marker

<i>Puccinia triticina</i> (<i>Pt</i>) races vary frequently, and new virulence races continue to emerge, leading to a lack of durable resistance in wheat cultivars. Therefore, monitoring avirulence gene composition and variation in <i>Pt</i> is crucial. In our previous study, we identified an avirulence protein AvrLr15 from <i>Pt</i> that induced <i>Lr15</i>-dependent immune responses and found that evasion of <i>Lr15</i>-mediated resistance in wheat was associated with a deletion and point mutations of amino acids in AvrLr15. In this study, TcLr15-Thatcher hybrid materials and <i>Lr15</i> mutant materials were developed, which further confirmed the reliability of <i>AvrLr15</i>. A duplex PCR assay using two primer pairs (M1-F/M1-R and M2-F/M2-R) designed based on the differences between <i>AvrLr15</i> and virulence gene <i>avrLr15</i> successfully differentiated avirulent and virulent races, which can be used as the <i>AvrLr15</i> marker. A total of 21 races with different virulence to <i>Lr15</i> were tested to confirm the reliability of the <i>AvrLr15</i> molecular marker. A total of 168 <i>Pt</i> isolates were collected from 15 provinces in 2024, and the <i>AvrLr15</i> molecular marker can monitor the distribution of the V15 (virulent to the <i>Lr15</i> gene) race and assess the durability of <i>Lr15</i>-mediated resistance effectively. Our findings developed the first <i>Pt</i> avirulence gene molecular marker to monitor natural <i>Pt</i> populations and guide the deployment of <i>Lr15</i>-resistant wheat cultivars in the field.