Pyramiding Strategy for Durable Resistance to Root-Knot Nematodes in Prunus Rootstocks: High-Resolution Mapping of a Peach Gene and Fine Mapping of an Almond Gene

Root-knot nematodes (Meloidogyne spp.) severely affect Prunus rootstocks for peach, plum, and almond. This study aims to combine three major dominant resistance genes (Ma, RMia, RMja) through pyramiding to achieve durable resistance. High-resolution mapping of the RMia gene was performed in the Nemared peach source using SSR and SNP markers in an F2 Montclar × Nemared population, locating it within a 92-kb interval in the Lovell peach genome with three TNL candidate genes. Fine mapping of the RMja gene in the Alnem almond source, based on an F2 Lauranne × Alnem population of 800 individuals, positioned it in a ~2 Mb interval containing the Ma ortholog. The upcoming NGS parent sequences will enable marker-assisted selection tools for all three R genes.