Diseases

Downy mildew of lamb's lettuce

Valerianella locusta (L.) Laterr.

A fungal disease of lamb's lettuce caused by the oomycete Peronospora valerianellae. It is characterized by the appearance of chlorotic spots on the leaves and the formation of a gray or purple coating on the underside of the leaf blade.

In the reference 11 varieties crop Corn salad, where this is mentioned in the description.

The pathogen Peronospora valerianellae is an obligate biotrophic pathogen that survives as oospores and is transmitted via seed material. On seedlings, the infection leads to leaf deformation, whereas on growing plants, yellowish spots form on the upper side of the leaf, eventually progressing to necrosis, while a fluffy sporulating coating develops on the underside.

In breeding practice and variety testing systems, the pathogen is classified by race. Officially, two races are used to evaluate variety resistance: Pv: 1 and Pv: 2. Varieties are tested using sets of differential lines, the results of which determine their resistance status, designated as HR for high resistance or S for susceptible forms.

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

Sources8

Varieties of Corn salad 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.