Preliminary fire blight resistance evaluation of pear genotypes as support for breeding.

An important factor that significantly limits the cultivation of pear trees in Europe is fire blight caused by the Gram-negative bacterium Erwinia amylovora. The selection of resistant or tolerant varieties and rootstocks is one of the main objectives of breeding programs worldwide in order to control and limit the disease spread. The final aim of this study is to identify candidate resistance genes and to develop new PCR-based molecular markers for the marker-assisted breeding of pear varieties. To this aim a pear population obtained from the “Abate Fétel” x “Old Home” cross is under testing for fire blight resistance in greenhouse. A total of 135 sibling genotypes and the two parental genotypes were bud-grafted on the commercial rootstock “Fox 11” in order to obtain shoots to be inoculated with a virulent E. amylovora strain. The strain to be used was selected through an experimental inoculation in “Abate Fétel” and “Conference” plants, among Italian strains isolated from pear in different times and in different regions, cross confirmed with infections on pear flowers. The strain OMP-1077/7.94, isolated from pear in 1994 during an epidemic outbreak has been used as reference strain in both the biological characterization and in the virulence test. Molecular analyses as SPET (Single Primer Enrichment Technology) genotyping analysis was conducted on the pear population and genetic maps were constructed for each parental genotype. According to genotypic and phenotypic data, a QTL analysis will be performed in order to localize E. amylovora resistance genes in the pear genome.