Research in seed-borne black spot disease in cruciferous vegetables.
Black leaf spot is an important fungal disease of Brassicacae worldwide. It caused severe losses in Northern China during the 1990s and is still a potential threat at present. Alternaria brassicae, A. brassicicola, and A. japonica are pathogens of black leaf spot. These pathogenic fungi can be identified using their morphology, genetic variation, nucleotide sequences, isoenzymes, and ELISA. Among these techniques, nucleotide sequence analysis is the quickest and most practical. Toxins produced by these fungi determine their pathogenicity. Molecular biology methods were used for detection and identification of the pathogens in seeds. Effective measures for disease control include seed treatment and use of fungicides with low phytotoxicity. Future investigations should be focused on the pathogenic constituents, disease epidemics, and methods for seed health testing at the molecular levels, as well as the improvement of biological control based of fundamental research and technological innovations.