Evaluation of morphology of infection structures in distinguishing between different Allium rust fungi

Three cultivars of white cabbage with different levels of resistance toMycosphaerella brassicicola were tested for seedbed infection. Seedlings grown in seedbeds, to which infected plant debris was added as an inoculum, showed typical ring spot lesions on the cotyledons and first two leaves before seedlings reached the transplanting stage, whereas non-inoculated controls had few lesions only. Differences in levels of resistance between cultivars were present in seedlings grown under field conditions. Disease severity of transplants at the end of the season reflected disease severity of seedlings before transplanting in each cultivar.To lower the risk of a severe epidemic of ringspot at the end of the growing season, the seedbed should be protected from infection byM. brassicicola.