ALTERNARIA BLACK SPOT OF CRUCIFERS: SYMPTOMS, IMPORTANCE OF DISEASE, AND PERSPECTIVES OF RESISTANCE BREEDING

Alternaria black spot of cruciferous vegetables, incited by different species of Alternaria, remains an increasing threat to Brassicaceae crops throughout the world, including Poland. Brassica plants are attacked by conidia of A. brassicae (Berk.) Sacc., A. brassicicola (Schw.) Wiltsh., A. raphani Groves & Skolko, and A. alternata (Fr.) Kreissler. The pathogens have a wide spectrum of hosts, such as head cabbage, Chinese cabbage, cauliflower, broccoli, and other crucifers includ-ing cultivated and wild grown plants. Alternaria pathogens usually cause damp-ing-off of seedlings, spotting of leaves of cabbages, blackleg of heads of cabbag-es, and spotting of cauliflower curds and broccoli florets. In oilseed rape, A. brassicae is the dominant invasive species, while in the cruciferous vegetables, both species, A. brassicae, and A. brassicicola are encountered. Infected seeds with spores on the seed coat or mycelium under the seed coat are the main means of distribution for these pathogens. The fungus can overwinter on susceptible weeds or crop debris and on seed plants, as well as on stecklings. Methods for disease prevention and control are based on combining agri-cultural management practices with chemical control. Using disease-free seeds or seeds treated with fungicides can greatly reduce disease incidence. After appearance of the first symptoms of disease, stringent fungicide spray program is an effective way to reduce losses. Many authors seem to agree, that the most economically feasible method of disease control is the development of resistant Brassicaceae crops varieties, as transgenic approach proved unsuccessful. Due to our increasing understanding of pathogen-host plant interactions, identifica-tion of resistance sources, and assessment of the resistance trait inheritance mode, breeding programs of Brassica crops for Alternaria resistance can be enhanced. This is of particular importance since recent years experience dynam-ic development of ecological and integrated plant production with an emphasis on plant biotic stress resistance. Highly resistant genetic resources have not been reported in Brassica cultivated species, although some varieties differ in their resistance/susceptibility level.