Diseases

Downy mildew of Swiss chard

Beta vulgaris Leaf Beet Group

A fungal disease of Swiss chard caused by the oomycete Peronospora farinosa f. sp. betae. It manifests as yellowing and deformation of young leaves and the appearance of a characteristic grayish-purple coating on the underside of the leaf blade.

In the reference 9 varieties crop Swiss chard, where this is mentioned in the description.

The causal agent of downy mildew on Swiss chard is the highly specialized oomycete Peronospora farinosa f. sp. betae (synonym Peronospora schachtii). The pathogen affects various varieties of Beta vulgaris, causing systemic infection of the aerial parts of the plant, which leads to premature leaf senescence and a reduction in overall crop yield.

Key symptoms include yellowing and thickening of young leaves in the center of the rosette, followed by their deformation and brittleness. Under high humidity conditions, sporulation appears on the underside of affected leaves as a coating, which may spread to the upper leaf surface.

Specific resistance genes in Swiss chard have not been identified, and the classification of pathogen races is not detailed. Breeding for resistance to this pathogen is challenging, and for most commercial cultivars, high resistance to P. betae is not a claimed trait.

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

Sources7

Varieties of Swiss chard 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.