Diseases

Downy mildew — Onion

Allium cepa L. var. cepa

A dangerous onion disease caused by the oomycete Peronospora destructor, manifesting in diffuse and local forms with the formation of a grayish-violet coating on the leaves.

In the reference 59 varieties crop Onion, where this is mentioned in the description.

The causative agent of the disease is the obligate pseudofungus Peronospora destructor. The disease affects all parts of the plant and proceeds in two stages: systemic diffuse, in which plants turn yellow and deform, and local, characterized by the appearance of chlorotic spots. Under conditions of high humidity and moderate temperatures, a grayish-violet sporulation coating develops on the affected areas, leading to necrosis and tissue death.

In breeding for resistance to the pathogen, the dominant gene Pd1 is identified, which is detected in genotypes using the molecular marker DMR1. Work on developing resistant forms is often based on interspecific hybridization, for example with Allium roylei; however, in widespread production, field resistance or tolerance of varieties is more common than absolute immunity.

General information about the subject — on the page Downy mildew.

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.