SEEDBED INFECTION OF WHITE CABBAGE BY MYCOSPHAERELLA-BRASSICICOLA

Three cultivars of white cabbage with different levels of resistance t o Mycosphaerella brassicicola were tested for seedbed infection. Seedl ings grown in seedbeds, to which infected plant debris was added as an inoculum, showed typical ring spot lesions on the cotyledons and firs t two leaves before seedlings reached the transplanting stage, whereas non-inoculated controls had few lesions only. Differences in levels o f resistance between cultivars were present in seedlings grown under f ield conditions. Disease severity of transplants at the end of the sea son reflected disease severity of seedlings before transplanting in ea ch cultivar. To lower the risk of a severe epidemic of ringspot at the end of the growing season, the seedbed should be protected from infec tion by M. brassicicola.