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Sobiczewski P.,Research Institute of Horticulture Pomology Division IO | Peil A.,Julius Kuhn Institute | Mikicinski A.,Research Institute of Horticulture Pomology Division IO | Richter K.,Julius Kuhn Institute | And 3 more authors.
European Journal of Plant Pathology | Year: 2014

The study was conducted in greenhouses at two locations on one-year old trees of apple cultivars and clones originating from genetic resources and breeding programs conducted in Belgium, Hungary, Germany, Poland, Sweden and Switzerland. At each location different inoculation method of trees with Erwinia amylovora was used. In Poland, at the Research Institute of Horticulture in Skierniewice (IO), the method of cutting-off shoot tips with scissors immersed in a single highly virulent strain of the inoculum (107 cfu ml−1) was applied for testing 38 genotypes. In Germany, at the Julius Kühn-Institut in Dresden and Quedlinburg (JKI), the method of cutting-off the tips of the two youngest leaves with scissors dipped in a suspension of three highly virulent strains at concentration of 109 cfu ml−1 was used for testing 27 genotypes. Observations and measurements of fire blight development on inoculated shoots were performed at 2, 4 and 6 weeks after inoculation at IO and after 4 weeks at JKI. Each genotype was evaluated over the course of two or three seasons. Of the total 40 genotypes, 25 were tested at both locations. The final assessment based on results of all tests was either similar or the same for 17 genotypes. MR 10, Pi-As 12,53 and Pi-As 50,74 were the most resistant. ‘Free Redstar’ and ‘Reanda’, tested only at IO, as well as Pi-As 36,164, tested only at JKI, were also classified as highly resistant. The following cultivars were found to be very susceptible at both locations: ‘Blauacher Wädenswil’, ‘Bohnapfel’ and ‘Idared’. Among those tested only at IO, CRA Ma A40, CRA Ma A68, CRA Ma A70, CRA Ma B28, CRA Ma D30 and ‘Jacob Level’ appeared to be also very susceptible. No significant differences in shoot necrosis length appeared when comparing the two inoculation methods used at IO and JKI (i.e. application of single strain vs. mixture of three highly virulent E. amylovora strains, at two concentrations) on four genotypes. © 2014, Koninklijke Nederlandse Planteziektenkundige Vereniging. Source

Peil A.,Julius Kuhn Institute | Wohner T.,Julius Kuhn Institute | Hanke M.-V.,Julius Kuhn Institute | Flachowsky H.,Julius Kuhn Institute | And 7 more authors.
Acta Horticulturae | Year: 2014

Fire blight, caused by enterobacterium Erwinia amylovora, is the most important bacterial disease affecting pome fruit. It can cause devastating economic losses and is reliably controlled only by the application of antibiotics, which are banned in many European countries due to environmental and sustainability issues and consumers' mistrust. One solution could be the utilization of fire blight resistant cultivars in apple production. In 2003, we started an approach at Dresden-Pillnitz to detect different mechanisms conferring resistance to fire blight aimed at their combination in new cultivars. Four segregating populations were established to map QTLs for fire blight resistance. The donors used were three wild species accessions of Malus baccata, M. fusca , M. xrobusta 5 and the Pillnitz cultivar 'Rewena'. The susceptible parent in each case was Idared. Grafted scions of each progeny were inoculated with E. amylovora strain Ea222-JKI. Average percent lesion length (PLL) of all progenies was determined. Genetic linkage maps were established using DArT-SCAR-, SNP-, and SSR-markers. Whereas in Rewena no QTL could be determined, major QTLs were detected in M. baccata on linkage group 12, in M. fusca on linkage group 10, and in M. xrobusta 5 on linkage group 3 explaining up to around 50, 85 and 85% of the phenotypic variance, respectively. The fact that all resistance QTLs are located on different linkage groups enhances the chance that different mechanisms are acting in the donors. Additionally, trees of the Idared by M. xrobusta 5 population were planted in an orchard and flowers were inoculated for phenotyping. The QTL on linkage group 3 could be confirmed after mapping. © 2014, International Society for Horticultural Science. All rights reserved. Source

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