Construction of a Linkage Map and Identification of Resistance Gene Analog Markers for Root-knot Nematodes in Wild Peach, Prunus kansuensis

Abstract

The root-knot nematode (RKN) Meloidogyne incognita can cause severe crop loss in economically important Prunus species like peach (P. persica), almond (P. communis), plum (P. salicina), and apricot (P. armeniaca). Some peach rootstock, including Nemaguard (P. persica), Nemared (P. persica), and Myrobalan plum (P. cerasifera), display significant resistance to RKN. We present a genetic linkage map constructed by using simple sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) for a peach backcross population (190 individuals) of RKN-resistant ‘Honggengansutao’ (P. kansuensis) and susceptible ‘Bailey’ (P. persica). Degenerate primers designed from conserved motifs of known plant resistance gene (R) products were used to amplify genomic DNA sequences. Twenty-two resistance gene analog (RGA) sequences were selected from 48 RGAs with open-reading frames to design sequence-tagged site markers. The linkage map of ‘Honggengansutao’ is composed of 138 loci (30 SSRs, 102 SRAPs, five RGAs, and one morphological marker for RKN resistance) assigned to eight linkage groups. The map covers 616 cM of the peach genome with an average marker spacing of 4.9 cM. The five RGAs were mapped to Groups 2, 7, and 8. One gene (designated PkMi) involved in resistance to RKN was mapped to Group 2 (which also includes the known RKN-resistance RMia gene). BLASTN analysis mapped all RGAs to the peach genome sequence. The map constructed in the study will aid future rootstock breeding with marker-assisted selection to identify additional candidate RGA sequences.