Blackleg is a complex of diseases affecting the basal zone of young plant stems, which triggers the appearance of constrictions, tissue water-soaking, and subsequent crop lodging. Depending on the plant species, the causative agents can be various fungi, oomycetes, or bacteria that induce rot, causing plants to lose stem strength and be easily pulled from the soil, while in the case of potatoes, they show signs of wilting and tuber decay.
Pathogen development is closely linked to soil conditions, such as high moisture, excessive watering, poor ventilation, and sharp temperature fluctuations. Agrotechnical factors, including dense planting and increased substrate acidity, significantly increase the risk of infection, which under unfavorable conditions is capable of destroying up to 100% of crops in a short period.
Variety resistance to blackleg is an important breeding trait, which in many crops has a polygenic nature and an additive mode of inheritance. Resistance evaluation in variety trials is conducted through artificial inoculation of tubers or stems under laboratory conditions, as well as through field observations in infection nurseries. The final degree of resistance is expressed in quantitative scores or percentage of infection, with tolerant forms being identified that are capable of maintaining productivity while infected.