Evaluation of Malus germplasm resistance to marssonina apple blotch

Marssonina apple blotch, caused by Diplocarpon mali (anamorph: Marssonina coronaria), is a serious disease of apple (Malus x domestica Borkh.). We evaluated the resistance of 28 cultivars and 39 species or biotypes after inoculating leaves with conidial suspensions in vitro and in vivo. Five accessions of the 28 apple cultivars showed a good level of resistance, while 16 displayed intermediate type. In contrast, resistance was good for eight accessions of species or biotypes and moderate for 19 accessions. Among these 67 candidates, more than 19 % had resistance against Marssonina apple blotch, indicating that resistant resources are abundant in that germplasm. These high-performing accessions can make valuable contributions to breeding programs for resistance against this disease.