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.

Soybean is an extremely valuable crop due to its unique biochemical composition, which underpins multifunctional utilization of this crop and high profitability of its industrial and agricultural production. Soybean seeds accumulate up to 45% of high-quality vegetable protein, which is close in composition to the protein of animal origin. Soybean is also of great importance as an oil-producing crop, accumulating up to 28% of oil in its seeds. It is widely used in animal husbandry for the production of maize-soybean silage and haylage. It can also be used as a green manure crop to enrich the soil with nitrogen at the expense of nodule bacteria. High demand and the price make it a highly profitable agricultural crop. It is clear from the above-mentioned advantages that soybean is of great interest to breeders. The Kuban Experiment station of VIR conducts field studies of new soybean cultivars using the practices worked out for leguminous crops at VIR. Three years of research have resulted in identification of promising cultivars, sources and donors of various valuable traits. This article is based on the data obtained from the study of the soybean collection from 2014 to 2016. Accessions k-11385, k-11479, and i-623931 were distinguished for their high yield. The following accessions stood out for their seed productivity per plant: k-1475, k-11472, k-11535, k-11466, k-11478, k-11577, k-11467, and k-11469. The size of seeds was the best in accessions k-11489, k-11491, k-11533, k-11529, k-11537, i-623952, i-623967, i-623980, i-623958, and i-623987. Two accessions appeared noticeable for the height of lower pod attachment: i-623960 and k-11494. All selected accessions can be used in breeding programs as sources of valuable traits.

Background. Soybean (Glycine max (L.) Merr.) is a microbiotic whose seeds quickly lose germination in uncontrolled conditions at room temperatures. This determines the need to preserve accessions in special conditions. Low temperature storage (LTS) allows to maintain high seed germination ability, but not for all accessions. Therefore, it is relevant to assess the results of LTS at the VIR Genebank and to make an attempt to determine the best geographical conditions for growing plants and harvesting seeds that will be subjected to LTS. Materials and methods. The work was carried out on 312 soybean accessions from the VIR collection, originating from almost the entire area of soybean cultivation. The accessions used in the research were reproduced at three VIR experiment stations (ES), namely Adler ES, Kuban ES (Krasnodar Territory) and the Far East ES (Primorsky Territory). The seeds were harvested in 1999 to 2017 and stored in sealed foil laminated bags at –10°C from 2002 to 2021. The accessions were removed from LTS and germination assessed in 2022. Results. At the beginning of LTS, seed germination (G_i) ranged from 12 to 100% (averaging 79.1%), while that after LTS (G_r) ranged from 1 to 97% (57.8% on average). The retention of germination ability was expressed as the germination index (GI = G_r / G_i), which ranged from 0.02 to 1.73 (an average of 0.72). All the indicators of germination in the range of up to 20 years of LTS were not associated with the duration of LTS and with the number of years before LTS (0.5-4 years in our research). The climatic conditions characteristic of the place of reproduction had a significant impact on G_i and G_r, but not on GI. The average G_i of seeds obtained at the Adler ES and Kuban ES did not differ significantly (77.4% and 75.7%), while that of seeds harvested at the Far East ES was significantly higher (84.0%). G_r of the accessions from the Far East ES (64.3%) was also greater than that of accessions from the Kuban ES (52.2%) and Adler ES (57.2%). The excessively high sum of temperatures above 10°C (recorded in some years at all stations) reduced G_i, G_r but had little effect on GI. The highest values of G_i, G_r, and GI were demonstrated by the accessions maturing in 101-120 days. Additionally drying of the most late-ripening accessions (later than 140 days) in sheaves under an awning yielded seeds with high germination ability and good LTS tolerance. Conclusion. The seeds from different places of reproduction of accessions differed in germination before and after LTS, and, on an average, the highest values were demonstrated by the seeds harvested at the Far East ES, where the temperature regime is closer to the optimal one for soybeans. The seed germination index showed relative independence from the conditions of reproduction of accessions, including the climate and weather conditions, as well as the initial germination ability and LTS duration.