Resistance to Didymella applanata in red raspberry and some related species

When raspberry canes were inoculated in summer with a mycelial inoculum of Didymella applanata resistant genotypes developed relatively small lesions which produced few fruiting bodies in the following spring. Scores of the frequency of these fruiting bodies provided the best discrimination between genotypes. Very strong resistance was found in R. pileatus, R. occidentalis and R. coreanus and in hybrids of these species with red raspberry. Hybrids with R. crataegifolius were less resistant. Resistance was also found in Malling 1473/35, a derivative of red raspberry cv. Chief, and in red raspberry segregates with gene H which determines cane pubescence. Both the expression of resistance and the ranking of resistance sources for their resistance was similar for D. applanata to that reported for Botrytis cinerea.