RT Journal Article SR Electronic T1 Characterization of the grape powdery mildew genetic resistance loci in Muscadinia rotundifolia Trayshed JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.11.23.469029 DO 10.1101/2021.11.23.469029 A1 Massonnet, Mélanie A1 Vondras, Amanda M. A1 Cochetel, Noé A1 Riaz, Summaira A1 Pap, Dániel A1 Minio, Andrea A1 Figueroa-Balderas, Rosa A1 Walker, M. Andrew A1 Cantu, Dario YR 2021 UL http://biorxiv.org/content/early/2021/11/24/2021.11.23.469029.abstract AB Muscadinia rotundifolia cv. Trayshed is a valuable source of resistance to grape powdery mildew (PM). It carries two PM resistance (R) loci, Run1.2 on chromosome 12 and Run2.2 on chromosome 18. This study identified the nucleotide-binding leucine-rich repeat (NLR) genes composing each R locus and their associated defense mechanisms. Evaluation of PM disease development showed that introgression of both loci confers resistance to PM in a V. vinifera background, but with varying speed and intensity of the response. To better understand the effect of NLR composition on PM resistance, both haplotypes of each R locus were reconstructed and the gene models within each haplotype were manually refined. We found that the number and classes of NLR genes differed between Run1.2 and Run2.2 loci and between the haplotypes of each R locus. In addition, NLR genes composing Run1.2b or Run2.2 loci exhibited different levels of gene expression, pointing to candidate NLR genes responsible for PM resistance in Trayshed. Finally, a transcriptomic analysis that included six additional R loci showed differences in the defense mechanisms associated with Run1.2b and Run2.2 in response to PM and at constitutive level. Altogether, our results reveal that Trayshed’s R loci are composed of distinct NLRs that trigger different plant defense mechanisms in response to PM and at constitutive level, which would explain the variation of pathogen restriction between the two loci.Competing Interest StatementThe authors have declared no competing interest.