Diseases

Rhizoctonia bottom rot of lettuce

Lactuca sativa L.

A soil-borne disease of lettuce caused by the fungus Rhizoctonia solani, manifesting in two forms: seedling damping-off and bottom rot affecting the head during the maturation period.

In the reference 7 varieties crop Lettuce, where this is mentioned in the description.

The pathogen is the fungus Rhizoctonia solani, which persists in the soil as sclerotia or saprotrophically on plant debris. In the context of lettuce infection, the pathogen is classified into anastomosis groups, among which AG-1-IA, AG-1-IB, and AG-2-2 are the most significant for the crop.

The disease manifests as seedling damping-off, accompanied by rotting of roots and stems, as well as in the form of bottom rot of the heads. The primary symptoms of bottom rot are rusty-brown spots on the lower leaves in contact with the soil; subsequently, the infection spreads to internal tissues, causing their maceration and necrosis under the influence of the pathogen's web-like mycelium.

Specific resistance genes to this pathogen in lettuce have not been identified. The main breeding approach is the selection of cultivars with a vertical head growth habit, which minimizes contact between the foliage and the soil surface and reduces the risk of primary infection.

General information about the subject — on the page Rhizoctonia.

Sources8

Varieties of Lettuce 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.