Rhizoctonia

Rhizoctonia manifests as sprout rotting, the formation of dark sunken ulcers on stems and roots, and the development of 'black scurf' or a mycelial mat in the near-ground area. During the vegetation period, leaf curling can be observed, and dense black formations known as sclerotia develop on the tuber surface.

Disease development depends on weather conditions, soil type, and agronomic practices, with a prolonged cold and wet spring being the most hazardous. The pathogen actively develops in heavy, acidic, and waterlogged soils, while its spread is facilitated by high plant density and the use of infected material.

In variety trials, resistance is evaluated by planting material in an artificial infection background with subsequent monitoring during the emergence, budding, and harvesting phases. The criteria include the degree of damage to sprouts, roots, and stolons, as well as the surface area of tubers covered by sclerotia compared to control samples.