Detection of QTLs in a Mediterranean climate associated with fire blight necrosis length in Pyrus communis using a high-resolution genetic linkage map

Fire blight caused by the bacterium Erwinia amylovora, is the most critical disease of European pear. Breeding of resistant cultivars is a possible solution for a growing demand for healthier alternative practices for disease control. In this study, we present a pear fire blight genetic study using a large F1 population. Quantitative trait loci (QTLs) were detected using a high-resolution genetic map, allowing detection of QTLs with small intervals. A total of 162 offspring crossbred between ‘Harrow Sweet’ (HS, low susceptibility cultivar) and ‘Spadona’ (SPD, high susceptibility cultivar) were studied. We detected a significant genotype effect (p <.0001), which explained 46.4% of the variance of the necrosis length. A major QTL of the main genotype effect (AVG) was detected at 8.8 cM in linkage group (LG) 2 (LOD = 7.7). Additional QTLs were detected in LGs 7, 13 and 15. These markers can greatly contribute to pear breeding programs in a Mediterranean climate and can shed light on potential candidate genes that control fire blight resistance.