Virulence Profiles and Genome-Wide Association Study for Isolates Collected from Australian Lentil-Growing Regions.

, the causal organism of Ascochyta blight (AB) of lentil (), has been shown to produce an avirulence effector protein that mediates AB resistance in certain lentil cultivars. The two known forms of the effector protein were identified from a biparental mapping population between isolates that have reciprocal virulence on 'PBA Hurricane XT' and 'Nipper'. The effector AlAvr1-1 was described for the PBA Hurricane XT-avirulent isolate P94-24 and AlAvr1-2 characterized in the PBA Hurricane XT-virulent isolate Kewell. Here, we performed a genome-wide association study to identify other loci associated with AB for a differential set of lentil cultivars from a diverse panel of isolates collected in the Australian lentil-growing regions from 2013 to 2020. The chromosome 3 locus was strongly associated with the PBA Hurricane XT, 'Indianhead', and Nipper disease responses, but one other genomic region on chromosome 11 was also associated with the Nipper disease trait. Our results corroborate earlier work that identified the locus for field-collected isolates that span the period before release and after widespread adoption of PBA Hurricane XT. A multiplex PCR assay was developed to differentiate the genes and to predict PBA Hurricane XT avirulence and pathotype designation in the diversity panel. Increasing numbers of the PBA Hurricane XT-virulent pathotype 2 isolates across that time indicate strong selection for isolates with the allele. Furthermore, one other region of the genome may contribute to the pathogen-host interaction for lentil AB.