The frost resistance of winter soft wheat is evaluated using direct laboratory freezing in the tillering phase or seedling stage, where plants are kept in refrigeration units until reaching critical temperatures of -19°C or -21°C. The result of such tests is the percentage of surviving plants, supplemented by indirect biochemical analysis methods, such as free proline content or the assessment of the autofluorescence level of seedling tissues.
Under field conditions, resistance is determined visually on a 5- or 9-point scale, where a high score indicates better overwintering. The frost resistance index directly determines the density of the productive stand and crop yield, depending on the sowing depth, which should optimally be 4–6 cm, as well as on the level of plant hardening and the conditions of autumn vegetation.
General information about the subject — on the page
Frost hardiness.