Pears are an important fruit crop in the temperate climate region. Their cultivation by commercial growers or home gardeners remains challenging due to different biotic and abiotic threats. One of the most important diseases of pear is fire blight, a bacterial disease caused by Erwinia amylovora (Burrill) Winslow et al. This harmful disease can only be effectively controlled with antibiotics, severe pruning of affected parts, or eradication of infected trees. To gain insight into the susceptibility/resistance of the pear germplasm maintained at the German Fruit Genebank (GFG), partners of the GFG holding pear collections, as well as the Obstaboretum Olderdissen and Fructus from Switzerland delivered material for phenotyping. A total of 239 pear accessions were phenotyped by artificial shoot inoculation. The severity of the disease is expressed as ratio of necrotic shoot to total shoot length, i.e. percentage lesion length (PLL). The average percentage lesion length of all accessions was 60.7, with a standard deviation of 41.6, and the median PLL of all accessions was 76.8. Twenty-five accessions had an average PLL of less than 20 and 90 accessions an average PLL of more than 80, with standard deviations of 20.0 and 19.2, respectively. Among the robust varieties were ‘Old Home’, ‘Rüti Birne’, ‘Milchbirne’, ‘Punktierter Sommerdorn’, ‘Schoggolabirne’, ‘Harrow Sweet’, and ‘Harrow Delight’. This study provides an overview of large number of pear varieties/accessions and their susceptibility to fire blight. In addition, the results provide useful information for growers as well as for breeders about robust varieties and potential new donors for breeding fire blight resistant pear varieties.
Maag et al. (Thu,) studied this question.