Genetic mapping of Cacopsylla pyri resistance in an interspecific pear (Pyrus spp.) population

Cacopsylla pyri (pear psylla) is one of the most serious pests of pear (Pyrus spp.) in Europe. It can cause high yield losses, and its control has become difficult since it has developed resistance to a wide range of pesticides. Pear breeders are developing new cultivars resistant to pear psyllids, and Asian species, such as Pyrus ussuriensis and Pyrus × bretschneideri, are good sources of resistance. Antixenosis and antibiosis resistance to psylla were both identified in pear; they may differ in the biological mechanism and probably have different genetic backgrounds. We crossed interspecific P. × bretschneideri × Pyrus communis hybrid PEAR3, resistant to pear psylla, with the susceptible European pear cultivar ‘Moonglow’ to obtain an F1 population for the genetic mapping of the resistance. Quantitative trait locus (QTL) analysis was carried out for antibiosis by measuring the number of surviving nymphs and the nymphal development, using a novel phenotyping protocol and a saturated genetic map made of single-nucleotide polymorphism (SNP) and microsatellite (simple sequence repeats (SSR)) markers. A stable QTL was detected on linkage group (LG) 8 of PEAR3 (R 2 = 17.2–39.1 %). In addition, QTLs were detected on LG5 (R 2 = 10.8 %) of PEAR3 and on LG15 of ‘Moonglow’ (R 2 = 13.7 %