Alternaria Leaf Spot — Red Cabbage

The primary causative agents of Alternaria leaf spot in red cabbage are the fungi Alternaria brassicicola, Alternaria brassicae, and Alternaria raphani. At the seedling stage, the infection causes necrotic stripes and spots on cotyledons and hypocotyls, which often leads to plant death. On adult plants, symptoms appear as dark, zonate spots with a characteristic loose, sooty mold of sporulation, surrounded by a yellow halo. In cases of severe infection, the affected leaf tissues dry out and drop, giving the leaf blade a shot-hole appearance.

Infection of the heads occurs both during the growing season and in storage, characterized by the appearance of a black mold on the outer leaves and the development of small black spots in the inner layers. Specific races of the pathogen have not been identified, and crop resistance is of a quantitative, polygenic nature, depending on the plant's morphological characteristics, such as the thickness of the epicuticular wax layer, and the biochemical composition of the tissues. The use of marker-assisted resistance genes in breeding red cabbage for this disease is currently unavailable.