Evaluation of potato cultivars in the greenhouse and field for resistance to powdery scab

Abstract

The reaction of 10 commercial potato cultivars to infection by Spongospora subterranea was evaluated in the field and in the greenhouse. Micropropagated plants were used in the greenhouse and seed pieces were used in the field. The relative susceptibilities of the cultivars when measured in the greenhouse and in the field were comparable. The overall severity of scab on tubers was 8 times higher in the greenhouse than the field. The relative susceptibilities of 3 standard cultivars (Kennebec, Katahdin and Russet Burbank) were consistent over 3 greenhouse trials. When comparing planting material in the greenhouse, the incidence and severity of scab on the progeny of micropropagated plants did not, in general, differ significantly from that on the progeny of seed potatoes. Furthermore, the incidence and severity of scab on tubers of the highly susceptible cv. Kennebec grown in the greenhouse were not affected significantly by type of potting mix (well-drained, compared with poorly drained which inhibited plant growth). Screening potato cultivars for resistance to powdery scab on a small scale in the greenhouse, using micropropagated plants, is suggested as a preliminary to the evaluation of cultivars in the field.