Preliminary identification of QTLs associated with fire blight resistance in pear

Erwinia amylovora, the causal agent of fire blight in pome fruits, is still one of the main threats of pear cultivation in Italy. The disease severely affects pear production especially when the weather conditions are favorable to the bacterium spreading. In pear germplasm different levels of fire blight susceptibility/resistance are described. The cultivar Old Home is known for its fire blight resistance and has been used in breeding. A mapping population (‘Abbé Fétel’ × ‘Old Home’) was studied to detect genomic regions associated with possible resistance to fire blight. A progeny of 133 individuals was phenotyped by inoculation via cut-leaf method, of actively growing shoots of potted grafted plants in greenhouse conditions with the E. amylovora isolate FP621 from pear. This isolate was selected as the most virulent among some old and recent Italian isolates through pathogenicity tests on pear potted plants. High resolution SNP-based genetic maps of the parental lines were produced via the SPET technology. The QTL analysis conducted with the phenotypic and genomic data allowed a preliminary identification of two QTLs for E. amylovora resistance in the ‘Old Home’ map. The obtained results are currently used to identify candidate genes and for developing a suite of molecular markers for DNA-informed breeding.