Mfu16 is an unstable fire blight resistance QTL on linkage group 16 of Malus fusca MAL0045

Abstract A strong fire blight resistance QTL ( Mfu10 ) was previously detected on linkage group 10 (LG10) of Malus fusca accession MAL0045, using several strains the causative bacterium, Erwinia amylovora . As no strain capable breaking MAL0045 has been found, we hypothesized that another locus contributes to its resistance. However, none with tested progeny. Here, an avrRpt2 EA mutant (Ea1038) chromosomal S-allele deleted and complemented less aggressive C-allele, used phenotype × ‘Idared’ We performed phenotype-genotype analyses first genetic map which is scarcely dense, a recently constructed saturated map. expected, LG10 Ea1038, as other strains. Interestingly, logarithm odds (LOD) thresholds 5.5 2.9, significant at genome-wide chromosome levels, respectively, Ea1038 LG16 Mfu16 in subset 76 individuals, but only Progenies carrying both were significantly more resistant than progenies LOD diminished 2.6 larger individuals. hypothesize present genome albeit unstable