Mapping Rm2 gene conferring resistance to the green peach aphid (Myzus persicae Sulzer) in the peach cultivar Rubira®

The green peach aphid (GPA), Myzus persicae (Sulzer), is a widespread pest insect that significantly reduces yield in peach orchards [Prunus persica (L.) Batsch]. Chemical control of the GPA population in the orchards showed little efficiency because of the development of resistance to most classes of insecticides. Biological control partially gave convincing results. Breeding for resistant peach cultivars is therefore a serious option to take into account for the development of sustainable pest management. Among the few available resistance cultivars, the rootstock peach Rubira (R) shows a strong induced antixenosis-type GPA resistance. This was demonstrated segregating as a single dominant gene. In order to investigate the genetic basis of resistance and develop molecular tools useful in breeding programs, a F-2 population derived from Rubira (R) also segregating for leaf color was grown and scored for GPA resistance under contrasted environmental conditions. An SSR-based genetic linkage map composed of 120 SSR loci spanned over a distance of 497.8 cM was then established. The GPA resistance mapped to a single locus at the bottom end of linkage group 1. We propose to name Rm2 the dominant allele of the underlying gene. Additionally, a reciprocal translocation was identified near the Gr gene controlling leaf color. The red-leaf parent Rubira (R) was demonstrated responsible for the translocation. This study provides the basis for future molecular analysis for the use of Rm2 in peach breeding programs against GPA in peach orchards.