The article presents results of characteristics studying for generative and vegetative parts of soft winter wheat in the conditions of autumn moisture shortage and in the conditions of optimal moisture supply. During the period of studies a dramatic difference of the levels of generative and vegetative parts of plants has been observed. As a decreased level of characteristics development has been noted, so its increasing, in particular, among the varieties of generative part. within 7.2% (thousand seed weight) to 42.6% (seed weight per ear). It is found that efficient development of generative organs is subject to variety bushing capacity, in particular at spring. The article also shows that stress conditions of autumn period influence late emergence of seedlings; however, that goes along increased level of some characteristics development at generative part. Obviously, during such years the selection of breeding material as per ear yield would not be efficient. The article, for the purpose of excluding negative consequences of selection, pays special attention to such characteristics as that not affected by stress environmental conditions. This indicates genetic stability of those characteristics, so their use as marker characteristics in yield specific breeding is advised.

Purpose. Substantiating the selection of potato varieties for their ecological plasticity and stability to grow in Polissia. Methods. Field, laboratory, analitycal and statystical ones. Results. Impact of weather conditions during the growing season on the stability of potato varieties was estimated by indicators of yield, starch content and collection over the years by determining the average, standard deviation, minimum, maximum values and range of variation. ‘Memphis’, ‘Faluka’, ‘Arsenal’ and ‘Evolution’ were distinguished from the studied potato varieties by high genetic stability – their deviation from the average variance marked «minus» had values that were significantly less than zero. ‘Faktor’, ‘Flamenko’ and ‘Evora’ varieties are plastic (deviation is close to ±0), ‘Kolomba’, ‘Arizona’ and ‘Voliumiia’ ones – very plastic (deviation is most distant from zero). The studied varieties were distributed by homeostasis as follows: ‘Arizona’, ‘Colombo’, ‘Factor’ and ‘Memphis’ are the most valuable. Conclusions. ‘Evora’ potato variety can be considered intensive in terms of yield. ‘Evolution’ and ‘Flamenco’ varieties formed stable yields, during the years of study the difference between their maximum and minimum yields was the least – 8.2 and 9.3 tons per ha, respectively. Environmental assessment according to Eberhart and Russell indicates a high genetic stability of such potato varieties as ‘Arizona’, ‘Volyumiia’, ‘Kolombo’, ‘Evora’ and ‘Flamenko’. Conditions of Zhytomyr Oblast Plant Varieties Studying Centre are the most favorable among the studied regions to cultivate potato varieties.