S14 - Session P6 - Evaluation of the resistance of apple cultivars to Diplocarpon coronariae

Authors: Sophie Richter *, Thomas Wöhner, Monika Höfer, Anne Bohr, Henryk Flachowsky, Sascha Buchleither

Apple blotch disease often causes damage in organically cultivated orchards. Infected trees are affected by foliar spots, which lead to premature defoliation prior to fruit ripening and overall reduced tree vigor. The disease is caused by the hemibiotrophic fungus Diplocarpon coronariae ((Ellis and Davis) Wöhner and Rossmann). Effective control of the fungus is possible but difficult due to restrictions on pesticide application especially in organic fruit growing. The cultivation of resistant apple cultivars would be an alternative to fungicides, due to a reduction of fungicide application and prevent the spread of the fungus. However, only a few studies have assessed the resistance of apple cultivars to apple blotch. About one thousand accessions of traditional and modern apple cultivars are maintained in the German national germplasm collection. For this purpose, we aim to assess the resistance of these apple cultivars to apple blotch disease. Artificial tests were performed to characterize the symptoms of the disease e.g. the expression of fruiting bodies and chlorosis. First obtained results show that differences in the susceptibility of apple cultivars exist and that there are cultivars exhibiting lower symptom expression of the disease. These apple cultivars can contribute to a sustainable management of the disease by plantation in orchards and in meadow orchards as well as utilized for breeding further resistant apple cultivars.