Variety tolerance is the ability of a plant to withstand pathogen infection or the influence of abiotic factors, such as drought or salinity, without a significant decrease in productivity. In contrast to resistance, where the plant blocks the development of the pathogen, a tolerant variety becomes infected and bears signs of the disease, yet its physiological processes allow it to maintain a satisfactory yield level.
Tolerance assessment is conducted under disease pressure conditions by comparing the yield of varieties with the same degree of infection. When analyzing diseases, rating scales are used, where varieties with a high degree of infection but an insignificant drop in yield are classified as tolerant. Physiological indicators of resistance to abiotic stresses include data on germination, root system development, and the condition of the photosynthetic apparatus.
The complex trait of tolerance is expressed through the yield reduction coefficient: the lower the drop in productivity under strong factor impact, the higher the indicator. It is agronomically important that tolerant varieties act as latent carriers of pathogens, contributing to their accumulation in the field, which requires increased attention to phytosanitary monitoring even when plants appear healthy.