The aim of the research is to clarify the methodology for assessing the resistance of hazel (hazelnuts) to stress factors on the basis of uniform approaches adopted in walnut farming. The assessment of resistance to biotic and abiotic factors has been carried out according to the methods recommended for the walnut, and the state of the vegetative and generative organs of hazel (hazelnuts) has been correlated with the program requirements. The result has been the development of 7 point assessment scales and the numerical values of the degree of damage correlated with them. Score 0 corresponds to the absence of lesions, 1 – lesions up to 5%, 2 – lesions up to 6–10%, 3 – lesions up to 11–25%, 4 – lesions up to 26–50%, 5 – lesions up to 51–75%, 6 – lesions more than 75% or death of the whole plant (depending on the studied indicator). The assessment scale for the winter hardiness of vegetative organs takes into account the degree of damage to the apical buds, annual shoots, branches of two years and older, the stem and the whole plant. Damage to male inflorescences is determined by the length of their dead part, to the female flowers – by the number of damaged ones, expressed as a percentage. The degree of drought resistance is revealed on the basis of studying the state of the entire plant, the percentage of damaged and fallen leaves. The influence of drought on the loss of food part is established by the degree of shrinkage of the kernel. Susceptibility to diseases and pests is estimated in percentage points separately for leaves by area, shoots in length, nuts by the ratio of damaged and undamaged ones. We have distinguished 6 groups of resistance, depending on the degree of vulnerability of varieties and forms of hazel (hazelnuts). It has been proposed to draw conclusions on the basis of at least three years of observations, and the final conclusion should be focused on specific breeding goals.
