Crops

Glycine max (L.) Merr. - Soybean.

Taxonomic position.

Family: Fabaceae Lindl., genus: Glycine Willd., species: Glycine max (L.) Merr. - Cherepanov S.K., 1995

Synonyms:

Phaseolus max L., Dolichos soja L., Soja hispida Moench., Phaseolus sordidus Salisb.,Soja japonica Savi, Soja viridis Savi, Soja angustifolia Miquel., Glycine hispida (Moench) Maxim., Soja max Piper, Glycine gracilis Skvortz.

Biology and morphology.

2n=40. The soybean is an annual herbaceous plant. It has a tap root system. A symbiotic apparatus is formed in its upper part in the soil layer up to 10 cm deep. Soybean root nodules are globe-shaped, 2 to 4 mm in diameter, up to 8 mm long. Seed-lobes issue from the ground. Soybean hypoctyl is green or tinged with violet. The stalk length varies from 20 cm with dwarf varieties to 200 cm with tall varieties. Most varieties have a stalk which is 60 to 110 cm high. The nature of the stalk growth allows to distinguish between two groups of soybean varieties 1) indeterminant varieties which have a growing terminal bud and a stalk which, under favorable conditions, keeps on growing and forming new generative organs for a long time; 2) determinant varieties with their stalks ending in a flower raceme and finishing their growth upon formation of the terminal raceme; these varieties grow and bear fruit more rapidly and mature earlier than indeterminant varieties. Nowadays attempts are being made all over the world to transform all existing soybean varieties into determinant ones. Stalks, branches and leaf stalks of most varieties are covered with brownish, yellow or gray down. Its color depends on particular genotype. Soybean flowers are small, almost odorless (and therefore seldom visited by insects). They are united in racemes located in leaf axils. Soybean ovary is unilocular. It has one carpel with a few growing ovules. Soybean pistil's style is rather short and slightly bent. The stigma is broad, flat and sticky. Soya beans are short 2.5 to 6 cm long. They are 0.5 to 1.5 cm wide. Each bean has two or three seeds, more rarely one seed or four seeds. The lower beans are fixed at the height of 2 to 3 to 20 to 25 cm. With most varieties they are fixed at the height of 12 to 17 cm. Beans' lower position entails losses at harvesting while higher bean positions decrease the yield of soya beans. Soybean seeds are globe-shaped, oval or flattened oval. Seed-lobes are yellow or more rarely green in color. Seed coats' color ranges from amber, yellow, and greenish to black, brown or speckled. Their surface is glistening or lusterless. Their hilum is large, oval, more rarely - linear. On dark-colored seeds its color imitates the color of seed coating. On light-colored seeds it is darker. 1000 soybean seeds weigh 40 to 250 g.

Ecology.

The soybean is a short-day plant. Farther up North the soybean blossoms later, its vegetative mass increases and its vegetation period grows longer. Very fast ripening varieties of the northern ecotype radically shorten their vegetation period and turn into low-yield dwarfs in lower latitudes. The soybean is a light-requiring plant. It needs rather high temperatures. Soybean seeds begin to germinate with soil temperatures of 8 to 10° C. Soybean sprouts survive morning and night frosts as low as 3° C. The optimal air temperature for soybean blossoming and seed formation is 17 to 25° C. Very fast ripening varieties of the northern ecotype are more cold-resistant. They may blossom and form beans at 14 to 16° C. The total of active temperatures (10° C and higher) during the vegetation of southern soybean ecotypes is 2800 to 3500° C. Very early maturing northern cultivars terminate their vegetation at the total of active temperatures of 1700-2000° C, duration of their vegetation depending on the intensity of temperatures in specific interphase periods. Soybean vegetation period lasts for 75-200 days and is divided into six main stages: sprouting, ramification, blossoming, bean formation, full ripening of the seeds, full maturity. For breeding purposes it is convenient to distinguish two stages of soybean vegetation: the vegetation period and the generative period. A very important biological feature of the soybean consists in its ability to coexist with root nodule bacteria of Rhizobium genus. Under conditions favorable for their symbiosis (pH 6.5 to 7, optimal soil humidity, adequate supply of macro- and microelements, optimal temperatures of 15 to 25° C, and the presence of a specific active virulent Rhizobium strain) the active symbiotic potential amounts to 25 to 30 thousand units, and the amount of nitrogen consumed from the air during the vegetation period is 200 to 250 kg per hectare. With slow growth of its above-ground mass and its powerfully developed root system the soybean survives quite well the lack of moisture during the first phase of its vegetation, even though these conditions hinder the formation of its symbiotic apparatus. During blossoming, bean formation and seed ripening the humidity of the plough-layer is over 65 %. The lack of moisture during this period leads to deterioration of root nodules. Therefore these soybean plants lack nitrogen and yield little. The soybean thrives on black earth. It does not survive on acid, saline and waterlogged soils. The soybean is a rigorous self-pollinating plant. 98 % its flowers are cleistogamic. Natural hybrids are 0.1 to 0.15 % of the whole population, sometimes their share is 0.5 %. The indeterminant soybean varieties have a dragged out blossoming period. It is contemporary to continuous growth of the main stalk and branches. First to appear are single flowers in the lower and middle parts of the main stalk. After 4 to 6 days the whole plant is fully in flower. On the determinant soybean varieties flowers appear almost simultaneously on the whole plant. At the beginning of flower buds' growth, the pistil's style is inclined towards the vexillum, the stigma is dry, and the anthers with their slower growth are arranged in a close circle below the stigma. Pollination of soybean plants takes place during early morning hours. In each flower anthers only take a few minutes to burst. Meanwhile violet corollae turn pink and white corollae turn cream-colored. Anthers of a whole population take 2 to 3 hours to burst. The burst bright-yellow anthers form a whorl round the stigma and close up over it. Pollen grains germinate 10 to 20 minutes after anthers burst. 20 to 30 minutes after the beginning of pollen germination the corolla opens up and its petals lose their elasticity. Corollae of pollinated flowers stay open during the following night and begin to wither the next day. After 1 ot 2 days corollae fall off. While corollae wither, ovaries begin to grow. After 2 or 3 days the bean appears from its calyx. Soybean plants typically drop off a lot of flowers (14 to 90 %) and beans (up to 40 %), which greatly decreases the yield. Beans fall off if there is a drought, due to lack of nutrients or a long daylight. Soybean precursors are: bastard fallow, early maturing cereals, perennial herbs.

Distribution.

The soybean is cultivated in 62 countries of the world. Over 20 years' time the areas sown with the soybean have increased 2.5 times and amount to 58 million hectares, soybean seed production has increased more that 4 times and amounts to about 100 000 000 000 kg. Till not long ago 96 % of lands sown with the soybean in the Russian Federation had been concentrated in the Far East - in Amur Region and in Khabarovsk and Primorie territories. Over the last few years soybean cultivation has become more widespread in the Crimea, in Northern Caucasia and in the Volga Region. In the former republics of the USSR the soybean is widespread in Moldova, in the Ukraine, in Georgia, and in Central Asian republics. In China cultivated soybean has been known since the 5th millennium B.C. Cultivated soybean's ancestor is the wild Glycine ussuriensis soybean variety with its huge natural habitat in China. Later soybean cultivation was introduced to Korea and Japan. In Europe the soybean was first cultivated in the 18th century. In Russia it first appeared in 1870s in the Far East. By now about 70 soybean cultivars have been approved for cultivation in various areas of the Russian Federation (Aurora, Armavirskaya, Belor, Vega, Venera, VNIIOZ 76, VNIIS 1, VNIIS 2, Zernogradskaya, Zakat, Lada, Primorskaya 13, Rassvet, Smena, SOER 7, Sonata, Yug 40, and others). The most recent cultivars are: Azovskaya, Ariya, Grinfi, Primorskaya 81, Yaselda. Most artificially bred soybean varieties belong to the Manchurian subspecies. They typically feature weak or medium reaction to daylight length variations, relatively strongly fixed lower beans, resistance to lodging, breaking of branches and bean bursting. They have a high protein and oil contents and yield a lot. They are the best source for soybean breeding. The soybean varieties of the Korean subspecies have racemes with many flowers. They yield a lot, but their beans tend to burst. The main breeding agencies are: Armavir experimental station of All-Union Research Institute for Oil-Bearing Crops, All-Union V.S. Pustovoyt Research Institute for Oil-Braring Crops, All-Union Soybean Research Institute, Primorie Research Institute for Agriculture, Far Eastern Research Institute for Agriculture, All-Union Research Institute for irrigated agriculture, Ryazan Research Institute of Technology Development of the agro-industrial complex, Ershov experimental station for irrigated agriculture, South-Eastern Research Institute for Agriculture, Siberian Research Institute for Agriculture.

Economic Value.

The soybean is a leguminous and oil-bearing crop. Soybean seeds contain 35 to 52 % protein and 17 to 27 % oil, vitamins A, B, C, D, E, and a number of enzymes. Soybean protein contains mostly easily soluble fractions (up to 94 %). It contains a lot of indispensable amino-acids. Its lysine contents is 9 times as high as that of wheat flour protein and 2 to 3 times as high as that of pea, chick-pea and fodder bean seeds. Besides that the soybean protein - glycitine - has a curdling ability. Soybean seeds are used to produce four, soya-based milk, soya curds and protein products of three kinds: concentrates containing 70 % protein, isolates (up to 90 % protein) and structured products analogous to meat products. These products are much cheaper than meat products but are equally nutrient and digestible. Soybean oil tastes good and is convenient for cooking. It consists of polysaturated fatty acids, indispensable for living organisms. The content of the most important linoleic acid is 50 to 60 %. It is directly related to linolenic acid contents (2 to 3 %), which imparts to soybean oil its characteristic smell and favors its rapid oxidation. Soybean oil is semidrying and is used for various purposes. Upon refinement it turns light-yellow, loses its smell and is widely used to produce margarine and confectionery. Soybean oil is used in soap-making to produce hard soap varieties. When mixed with linseed-oil soybean oil is used in varnish and paint industry. Soybean green matter, hay, oilcakes and oilseed meal are used as livestock fodder. Its ability to fix nitrogen makes the soybean a valuable precursor of cultivated and cereal crops. The soybean is sown (by itself or together with maize, etc.) into well-heated soil with wide-row or band techniques. 35 to 140 kg of seeds are planted per hectare at the depth of 4 to 7 cm. Fertilizers are: 40,000 kg of manure per hectare and 45 to 60 kg of P₂O₅ per hectare or 110 to150 kg of NPK per hectare. The soybean is gathered in by direct mechanized harvesting. The soybean yields 2,000 to 4,000 kg per hectare. In irrigated areas of Central Asian republics the soybean yields 3,500 to 4,000 kg per hectare. The best soybean yields achieved in the USA are 7,000 kg per hectare.

References.

State Register of Breeding Achievements Approved for Practical Application in the Russian Federation in 2004. Moscow: 2004, p. 54-55
Zhukovsky P.M. Cultivated Plants and Their Congeners. Leningrad: 1971. p. 310-312
Particular Breeding of Field Crops. Ed. Konovalov Y.B. Moscow: 1990. p.269-284
Cherepanov S.K. Vascular Plants of Russia and Neighboring Countries. St. Petersburg: 1995, p. 468

© Gashkova I.V.