Alternaria Leaf Spot — White Cabbage

The disease is caused by the fungi Alternaria brassicae, Alternaria brassicicola, Alternaria raphani, and Alternaria japonica. In the conditions of the southern regions, particularly the Krasnodar Territory, Alternaria brassicicola is recognized as the most dangerous pathogen. In the life cycle of the species Alternaria brassicae, an ascomycete stage, Phleospora herbarum, is sometimes distinguished.

Symptoms on seedlings manifest as black necrotic streaks on cotyledons and hypocotyls. On adult plants, zonate spots with a yellow halo and sooty sporulation appear on the leaves; as they dry, the center of the spots falls out. During the storage of heads, the disease develops into a form of black rot.

Specific resistance genes to this disease in white cabbage have not yet been described. In breeding practice, the concept of tolerance is used, and the degree of hybrid infection is assessed by field methods on an infectious background, most often using a 4-point scale.