Genetic mapping of pear sawfly ( Caliroa cerasi ) and pear blister mite ( Eriophyes pyri ) resistance in an interspecific pear family

Whilst minor pests of pear, both sawfly larvae (pear slug) and pear blister mite can at times cause sufficient damage in commercial and particularly in organic pear production for treatment to be required. In the course of breeding new pear cultivars, resistance to both pests was identified in an interspecific pear family raised from a cross between ‘PremP003’ and ‘Moonglow’. The replicated seedling family was subjected to uninhibited insect development for both pests in an insect-proof cage, providing ample infestations for resistance segregation. Using an existing genetic map for the family, one major quantitative trait locus (QTL) for resistance to pear blister mite was located to linkage group 13 (LG13) of ‘PremP003’. For pear slug, we mapped three QTLs for oviposition antixenosis, one each on LG7 and LG9 of ‘Moonglow’ and another on LG10 of ‘PremP003’, and one resistance QTL for leaf damage to LG9 of ‘Moonglow’ at a distance of 8.1 cM below the oviposition QTL. Incorporating these resistances into future cultivars could contribute to a reduction in pesticide use in pear production, especially in combination with the resistances for pear psylla ( Cacopsylla pyri ) and fire blight ( Erwinia amylovora ) recently mapped in the same population using marker-assisted selection.