Evidence of apple blotch resistance in wild apple germplasm (Malus spp.) accessions

Diplocarpon coronariae causes apple blotch, which results in significant economic losses. Resistance to apple blotch in commercial apple cultivars has not been reported in recent literature. The Malus germplasm collection from the Fruit Genebank of the Julius Kühn-Institut that is maintained in Dresden, Germany consists of 516 accessions of about 49 Malus species. This apple gene pool was evaluated for resistance to Diplocarpon coronariae. A four-year field survey was subsequently followed by artificial inoculation of field-selected accessions. Fifteen accessions that represent nine different species and hybrids were confirmed to be highly resistant following a repeated inoculation assay in the laboratory. The results from this investigation is of high interest to breeders for future apple breeding programmes and investigations of resistance to Diplocarpon coronariae.