Diseases

Downy Mildew (Peronospora) — Welsh Onion

Allium fistulosum L.

A fungal disease caused by the oomycete Peronospora destructor, affecting all organs of the Welsh onion. The crop often acts as a reservoir for the pathogen, which overwinters in the roots and plant tissues.

In the reference 12 varieties crop Welsh onion, where this is mentioned in the description.

The causative agent of the disease is Peronospora destructor, which affects the Welsh onion both systemically and locally. In cases of diffuse infection, plants infected via overwintering mycelium exhibit stunted growth, acquire a glossy appearance, and become distorted. Local infection manifests on leaves as oval or cylindrical spots with a grayish-violet bloom during high humidity, which leads to the drying of the leaves (scapes).

In breeding practice, efforts are being made to combat the disease through interspecific hybridization of the Welsh onion with other species of the genus Allium to select resistant forms. In particular, the possibility of introducing the Pd1 resistance gene identified in the wild species Allium roylei is being investigated; however, no widely accepted commercial varieties with fixed resistance genes have been identified at this time.

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

Sources8

Varieties of Welsh 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.