For a targeted search of initial breeding material for the quality of soybean seeds, it is necessary to know the patterns of the dependence of the corresponding seed characters on the weather and climatic conditions in a particular region. Global climatic change, the concretization of which is relevant, has a share in this dependence. Thus, the aim of this work was to identify the relationship between the variability of protein and oil content in soybean seeds with climatic parameters in the North Caucasus as well as trends in this variability over a long time period. The study of 1 442 soybean accessions from VIR collection in the Krasnodar region during 1987–2015 had been carried out and the tendencies of the variability of protein and oil content in seeds in this environment were estimated. The regression analysis in differences with forward stepwise selection of variables has been used to construct models for the dependence of the protein and oil content on generalized agrometeorological indices. During 1987–2015, for the period with temperatures above 10 °C, the sums of active temperatures increased by 218 °C/10 years and precipitation decreased by 20.9 mm/10 years. In the dynamics of protein content, a trend has been revealed as an increase by 2.5 % over 10 years, while there is no reliable trend in oil content. The maximum average mean of oil content and the smallest protein were in the middle-maturing accessions (22.2 and 38.8 %), and a relatively high protein content was detected, on average, in the early- (21.6 and 40.0 %) and late-maturing (20.2 and 39.9 %) varieties. The protein content had been increasing with a growth of the duration of the period with temperatures above 22 °C and decreasing with a raise in precipitation over a period of temperatures above 18 °C. The accumulation of oil in seeds was promoted by an increase of the hydrothermal coefficient over the period with temperatures above 19 °C, and, in late-maturating varieties, prevented by a prolonged autumn period with temperatures below 15 °C. Long-term growth in protein content is due to both climatic change and genetic improvement of varieties.

In view of climate change and the active extension of soybean cultivation in Russia, the identification of yield-limiting factors has become a relevant task. The objective of this study was to identify the climatic factors associated with the variation in soybean productivity under the contrasting eco-geographical conditions of the Krasnodar (KR) and Primorye (PR) territories of Russia. An analysis of 424 soybean varieties from the global collection of the N.I. Vavilov Institute (VIR) at experimental stations in KR and PR in 1987–2005 showed that the soybean yields were higher and time to maturity was longer in KR than in PR, while the 1000 seed weight, on average, was irrelevant to the place of cultivation. The agrometeorological regression models of the observations in 1972–2017 of varieties accepted as the standards showed that the yield in PR was positively related to the sum of the temperatures above 10 °C and negatively related to precipitation in October, while in KR it was positively related to the hydrothermal coefficient. The stability of the soybean yield and of the time to maturity were higher in PR than in KR. Under the conditions of increasing temperatures and the absence of reliable trends for precipitation, a lack of moisture becomes a significant disadvantage for soybean in KR, while in PR conditions are improving.

Soybean [Glycine max (L.) Merr.] is produced in 93 countries of the world on 120.5 million hectares. The production area of the crop is located between 56N. (Russian Federation) and 35-37S (Argentina). In the gene pool of the crop, there is a wide variety of genotypes of different maturity groups, which every has a relatively narrow latitudinal adaptability, which depends on heat and moisture supply and the duration of photoperiod. An urgent problem of our time is the creation of early maturated varieties which allow to expand soybean cultivation to the north. In soybean 12 major loci (E1E11 and J) have been identified, which control the flowering initiation and the response to the photoperiod. The time of maturation, photothermal response and, ultimately, the adaptation of the crop to different latitudes also depend on various allelic combinations and the interaction of these loci. All these loci have been mapped, and for some of them genes have been identified, their allelic diversity has been characterized and the mechanisms of their functioning and interaction have been described. But the molecular-genetic nature of the early maturity of soybean has not yet been revealed in detail. This review presents the current understanding of the structure and nature of the interaction of molecular genetic determinants of early maturity of soybean, which regulate the timing of its flowering and maturation at different photoperiods and their influence on other plant traits, including the type of growth and productivity. As a result, an idea of the optimal genotype for northern latitudes was proposed, with a combination of alleles providing the earliest flowering and maturation in relatively northern regions with a long day.

New nonlinear regression models were developed to predict climatic factor dependences of the periods of time from sowing to seedling emergence and from seedling emergence to flowering in soybean. The...

The photoperiod and temperature sensitivity of the onset of flowering in 106 soybean accessions from the VIR collection has been studied for 8 years in a vegetation experiment in the conditions of Leningrad Province at 59°N, the northernmost point of soybean evaluation in the world. The accessions were previously field-assessed for the ability to form fully developed seeds in this region. The experimental conditions were extreme for soybean in terms of both photoperiod and heat supply. The emergence to flowering period length (LEF) in the sample set was 7.9 days longer, and the sum of the temperatures required for the transition to flowering was 143.2 °C higher, on an average, under the natural long day (LD) compared to those under the artificial short day (SD). The photoperiod sensitivity of the accessions was estimated as the ratio of LEF under LD (T1) to LEF under SD (T2), and expressed as the coefficient of photoperiod sensitivity Cphs = T1/T2. A coefficient of 1.25 was taken as the limit of a very weak photosensitivity. Varieties with a coefficient not higher than this value totaled 73.6% of the sample set. The dominating influence of weather conditions over the photoperiod for the reference variety 'Svetlaya' is shown for over 8 years of observations: weather conditions caused 84.3% of the LEF variability, while the differences in the photoperiod determined only 9.9% of variability. Excessive precipitation in 2016 and 2017 caused a significant delay in flowering. Cphs proved to be a stable characteristic of a variety because it did not differ significantly in contrasting years. A broader regional adaptability of varieties created in high latitudes compared to those of southern origin is discussed.