Abstract

Useful resistance was found in cv. Latham but its effectiveness was affected by the growth stage reached at inoculation and by kind of inoculum used. It was effective when field-grown canes were inoculated in mid-Aug. but less so when inoculated in early July, and more effective against a spore inoculum than a mycelial one. Resistance was inherited as a dominant multigenic character, but there were interactions between parents and 2 very favourable combinations were found. Rubus pileatus, R. mesogaeus, R. coreanus and R. lasiocarpus showed resistance when inoculated in pot tests; F1 hybrids obtained by crossing them with raspberry were largely susceptible. The problems of using these resistance sources in breeding are discussed.