A rhizome is an underground organ that provides a plant with the ability for vegetative propagation and survival under adverse conditions through the accumulation of nutrient reserves. The presence of rhizomes allows a crop to maintain viability when the above-ground part dies off, which increases the plant's overall resistance to drought or low temperatures.
Rhizome assessment in variety testing is conducted to confirm the distinctness, uniformity, and stability of a variety. Specialists record the presence, shape, growth direction, and depth of the underground organs based on the official variety description. In the case of vegetative crop propagation, spatial isolation standards are determined taking into account rhizome length to prevent mechanical mixing and undesirable spreading.
Indicators of rhizome development are considered species-specific, so universal criteria for their evaluation do not exist. In cases where the rhizome is the target part of the harvest, for example, in a number of medicinal crops, productivity is assessed through the mass of underground organs. In other situations, agronomic practices are planned based on the variety description, considering its potential for vegetative propagation and the need for weed control.