Diseases

Alternaria Leaf Blight of Onion

Allium cepa L. var. cepa

A fungal disease of onion caused by Alternaria porri, characterized by the appearance of lanceolate lesions with concentric zonation on the leaves and the development of neck rot in bulbs.

In the reference 6 varieties crop Onion, where this is mentioned in the description.

The primary pathogen of the disease is the fungus Alternaria porri, although other species of the genus Alternaria, including A. alternata, may also participate in the infection process. The pathogen exhibits high variability in aggressiveness, but a clear classification into races in a breeding context has not been defined.

Symptoms on leaves begin as small, water-soaked spots that expand into elliptical lesions with characteristic concentric zonation and a yellowish halo. Affected leaves lose their structural integrity, collapse, and die. When the infection reaches the bulbs through the neck, the tissues become watery and develop a brownish-purple discoloration, which leads to rot during storage.

Specific resistance genes to this pathogen in onion have not been identified. In breeding programs, varieties are evaluated based on criteria of general tolerance or complex resistance, as marker-assisted selection methods for this disease have not been developed.

General information about the subject — on the page Alternaria blight.

Sources8

Varieties of Onion mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.