A candidate gene of Malus x robusta 5 for breeding towards fire blight resistance

; ; ; ; ; ; (). A candidate gene of Malus x robusta 5 for breeding towards fire blight resistance. Acta Hort. (ISHS), 976 573-575.

Fire blight (FB) is the most important bacterial disease in apple and pear orchards. The disease is caused by Erwinia amylovora and difficult to control because the application of antibiotics is either banned or undesired in many apple production areas. Current breeding programs introgress strong resistance from wild sources such as Malus × robusta 5 (MR5). Previous work attributed the resistance derived from this accession to a QTL located on top of linkage group 3. We enriched this region with molecular markers and isolated the region by means of a genomic library. The genomic sequence encompassed by two flanking markers was analysed in silico and led to the identification of a gene with structural homology to known bacterial resistance genes in model plants. It is differentially expressed in fire blight resistant and susceptible plants, respectively. We therefore indicate it as candidate fire blight resistance gene MR5.