SUMMARY
In recent years, there has been a significant change in climatic conditions affecting the cultivation and yield of winter wheat. Therefore, the creation of wheat varieties with high adaptive potential is one of the main tasks of modern breeding. A significant component of the overall adaptive potential of winter wheat is winter hardiness, which is determined by a set of characters enabling plants to overwinter. To a large extent, winter hardiness is determined by gene systems that control vernalization requirement duration, photoperiod reaction, and frost resistance. The research is aimed at determining the features of modern winter wheat varieties developed at the V. M. Remeslo Myronivka Institute of Wheat of the National Academy of Agrarian Sciences of Ukraine in terms of winter hardiness components and adaptive potential in the environment of the Central part of the Ukrainian Forest-Steppe. Winter bread wheat varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska were studied. They also were crossed on incomplete diallele scheme with three near-isogenic lines derived from Erythrospermum 604 with different alleles of Vrd genes 1) Vrd1Vrd1vrd2vrd2, 2) vrd1vrd1Vrd2Vrd2, and 3) vrd1vrd1vrd2vrd2. It was established that vernalization requirement duration in the varieties Estafeta myronivska and Balada myronivska was short whereas in the varieties Hratsiia myronivska and MIP Assol it was medium. All the varieties studied have medium photoperiod sensitivity. The results of the hybridological analysis indicate the absence of the Vrd1 and Vrd2 genes in the varieties. Frost tolerance of these varieties is at the same level and higher than in the highly tolerant to the low temperatures variety Myronivska 808. Thus, the results indicate the possibility of recombining different levels of expression of these traits in genotypes by breeding efforts. This has great practical importance in farming, because in recent years the areas of crops harvested late (corn, sunflower, etc.) in the production conditions has significantly increased. It causes a shift in sowing dates of winter wheat to a later period. In this case, varieties Estafeta myronivska, Hratsiia myronivska, MIP Assol, and Balada myronivska are able to undergo sufficient hardening, to satisfy the vernalization requirement, and to form a high level of winter hardiness. Their relatively medium photoperiod sensitivity allows vegetation to be restored a little earlier in the spring and winter reserves of moisture to be used more effectively.