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Natural habitat of spring wheat had been evolutionary widening through the selection of adaptive vrn, vrd and ppd genes mutations (controlling vernalization requirement and photosensitiveness) to the Northern moderate latitudes. By those means winter wheats arose with their adaptation to overwintering autumn seedlings on the stage of tillering. And such masterpieces of domestic breeding as Odess- kaya 16 or Mironovskaya 808 were characterized with the high in- dices of those properties. With the appearance of Bezostaya 1, and afterwards through the wide introduction to the breeding programs of spring Mexican semidwarf stocks the breeders gave constantly greater advantage to lowly photosensitive lines. And for today more than 90% advanced breeding lines of the Institute are almost insensi- tive to photoperiod. Sure, the breeders have certain reasons for this preference leaning on the number of economic advantages of such genotypes (spring veg- etation starts earlier, more effective utilization of moisture accumu- lated in winter, higher productivity). However, the low photosensitiv- ity resulted simultaneously in reduction of vernalization requirement through physiological and biochemical interactions, in the accelera- tion of initial growth and development during autumn (leading to the decline of adaptiveness in winter), in the necessity of shifting sowing dates on later terms. During more than last 15 years we carry out the estimation of photosensitivity and vernalization duration indices in modern culti- vars and advanced breeding lines of the Institute. Experiments are conducted by planting 5-days green seedlings (artificially vernalized beforehand in growth chambers with the variants of different dura- tion) in natural from the end of April and shortened to 10 hours photoperiods. The estimation of these indices has been carried out by comparison of average stocks’ heading dates in various variants of vernalization durations and photoperiods. For result discussion the stocks have been distributed on 3 groups after each index: lowly photosensitive – 5-15 days; middle one – 15-25 days; highly sensitive – 25-35 days; and groups on duration of vernalization requirement: till 45 days, near 50 days and more than 55 days. The sets of evaluated stocks created in the breeding laboratory and the department of the Institute did not differ after their distribution