NLR1 is a strong candidate for the Rm3 dominant green peach aphid (Myzus persicae) resistance trait in peach.

The green peach aphid (GPA), Myzus persicae, is a polyphagous, sap-sucking aphid and a vector of many plant viruses. In peach, Prunus persica, three individual dominant GPA resistance loci have been genetically defined (Rm1-3), but knowledge of the underlying genes is limited. In this study, we focused on the Rm3 locus. Bulk segregant analysis (BSA) mapping in segregating progeny populations delimited Rm3 to an interval spanning 160 kb containing 21 genes on chromosome 1. RNA-seq data provided no evidence of candidate genes, but chromosomal structural variations were predicted around a nucleotide-binding site-leucine-rich repeat (NLR) gene (ppa000596m) within the Rm3 fine-mapping interval. Following bacterial artificial chromosome (BAC) library construction for a GPA-resistant peach cultivar and the sequencing of three target BAC clones, a chromosomal structural variation encompassing two novel TIR-NLR-class disease resistance (R) protein-coding genes was identified, and the expressed NLR gene (NLR1) was identified as a candidate for M. persicae resistance. Consistent with its proposed role in controlling GPA resistance, NLR1 was only expressed in the leaves of resistant peach phenotypes. A molecular marker that was designed based on the NLR1 sequence co-segregated with the GPA-resistant phenotype in four segregating populations, 162 peach cultivars, and 14 wild relatives, demonstrating the dominant inheritance of the Rm3 locus. Our findings can be exploited to facilitate future breeding for GPA-resistance in peach.