Physiological features of northern soybean ecotype varieties cultivated in the conditions of the central black earth region

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In 2017–2019 on 7 soybean varieties and 2 breeding lines of FSBSI «Federal Scientific Center of Legumes and Groat Crops» (FSBSI FSC LGC) the physiological mechanisms of adaptive reactions of soybean plants in contrasting meteorological conditions, influencing the formation of productivity, have been studied. The optimal area of soybean leaves for the formation of high grain productivity in unfavorable conditions of lack of heat and excess of moisture is 50 thous. m 2 /ha; in favorable conditions of a warm year with sufficient moisture supply, this indicator increases to 100 thous. m 2 /ha. In favorable weather conditions, the proportion of leaves and beans in the total plant mass increases. The adaptive reactions of the pigment complex consist in an increase in the content of chlorophyll b and carotenoids under conditions of drought and excessive illumination and carotenoids under high humidity and lack of heat and light. Two groups of varieties have been identified: 1. early ripening Lantsetnaya, Krasivaya Mecha, Osmon', distinguished by a balanced distribution of plastic substances in conditions of excessive moisture and forming a grain yield at the level of 2.5–2.8 t/ha; 2. middle-ripening Zusha, Mezenka, L-85, under these conditions, forming a large area of leaves and a mass of nodules, which leads to a decrease in grain productivity to 1.9– 2.2 t/ha. The early ripening varieties Lantsetnaya and Krasivaya Mecha have a balanced distribution of plastic substances and are able to form a high yield, both with an excess of moisture and a lack of heat, and in arid conditions. Line L-85, characterized by high values of photosynthetic and symbiotic parameters, formed the maximum yield of dry matter (12.3 t/ha) and grain (2.8 t/ha) on average over 3 years. The greatest amount of nitrogen in the vegetative organs of soybeans and in the grain accumulates in years with high humidity in comparison with favorable conditions of the growing season. Effective assimilation activity of leaves, active nitrogen fixation of nodule bacteria lead to increased accumulation of nitrogen in the grain. By the amount of crude protein in grain, the varieties Krasivaya Mecha (42.5%), Shatilovskaya 17 (41.2%) and the L-216 line (41.3%) were distinguished; for the collection of protein with a grain of 1.1 t/ha — Krasivaya Mecha and line L-85. A high positive correlation was found between the yield of the aboveground mass and the photosynthetic potential and leaf area at the level of r = 0.8–0.9; with a mass of nodules at the level — r = 0.6–0.8 for all 3 years of research. A close relationship between grain productivity and photosynthetic and symbiotic indicators was noted in a favorable 2018 at the level of r = 0.7–0.8.