Page 60 - Book of Abstracts

5 International Scientific Online Conference DOI: https://doi.org/10.15414/2021.9788055224015

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STUDY OF CULTIVATION CONDITIONS OF BRADYRHIZOBIUM JAPONICUM STRAINS
Iryna Gumeniuk, Alla Levishko, Viktoria Tsvigun, Oleksandr Botsula,
Olena Demyanyuk, Olena Sherstoboeva
Institute of Agroecology and Environmental Management of National Academy of Agrarian
Sciences of Ukraine, Kyiv, Ukraine; E-mail.: gumenyuk.ir@gmail.com
Soybean is a unique plant, it can be called a natural factory, thanks to a successful
combination of two important processes: photosynthesis and biological nitrogen fixation. It
helps to improve the nitrogen balance of the soil, is a good precursor for other crops, provides
clean products. The phenomenon of soybeans is a high content of protein and fat in the seeds,
a rare and diverse combination of enzymatic and vitamin composition.
Inoculation of soybean seeds by nodule bacteria is an integral part of its cultivation
technology. The use of bacterial fertilizers can improve the conditions of nitrogen nutrition of
this crop, increase its yield, the protein content in the seeds and reduce the number of mineral
nitrogen fertilizers. The result of legume-rhizobial symbiosis (LRS) is a sharp increase in plant
production without the need to add mineral fertilizers. It should be noted, that the value of this
symbiosis is also in ensuring the control of weeds, pathogens, and insects during harvesting in
the agricultural system. In a symbiotic association with Bradyrhizobium japonicum, soybean
plants can fix up to 200 kg/ha of molecular nitrogen, reducing the need for expensive and
potentially harmful nitrogen fertilizers. Therefore, the creation of highly efficient B. japonicum
nitrogen-fixing systems – has great theoretical significance and practical value.
The study aimed to investigate and determine the components and their concentrations
for the nutrient medium that would be most suitable for the cultivation of soybean bacteria
Bradyrhizobium japonicum.
It is known that yeast-mannitol agar (YMA) of the following composition is used for
growing the rhizobia (g/l): mannitol – 10.0; yeast extract – 1.0; sucrose – 3.0; (NH4)2SO4 – 0.5;
K2HPO4 – 0.35; KH2PO4 – 0.5; MgSO4 – 0.2; pH 7.2. Our task was to modify this medium to obtain
a significant increase in the biomass of soybean rhizobia.
The growth activity of B. japonicum strains, which were given the name BR-1 and BR-2, in
aYMA medium, which included sources of various nutrients, was studied. We set the following
levels of medium components: molasses: 8.0; 16.0; 21.0 g/dm ;
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fodder yeast: 2.5; 3.5; 5.0 g/dm ; phosphates (1:1) (KH2PO4 + K2HPO4):
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0.2; 0.3; 0.4 g/dm . Cultivation was performed in 250 ml Erlenmeyer flasks, under conditions
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of constant stirring using an orbital shaker 180 rpm, a temperature of 28 ±2 °C. The optimal
environment was determined at different periods of bacterial growth using a ULAB 102UV
Spectrophotometer at maximum absorption (600 nm) and built growth curves. It was found
that the maximum effect of molasses for the growth of BR-2 strain was obtained at its
concentration of 21 g/dm , concerning the BR-1 isolate – at a concentration of
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15 g/dm . The maximum effects on yeast extract exposure were observed using a component
concentration of 3.5 g/dm for both isolates. In the study of the effect of different content of
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phosphoric acid salts on the growth of B. japonicum, the greatest effect was obtained using the
minimum concentration of this component – 0.2 g/dm .
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Therefore, according to the growth rates of B. japonicum strains, it was found that the
optimal ratio of components and concentrations are: molasses: 18.0 g/dm ; fodder yeast: 3.5
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g/dm ; phosphates (1:1) (KH2PO4 + K2HPO4): 0.2 g/dm . The optimized medium promotes the
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growth of biomass of isolated strains – the formation of a significant amount of
exopolysaccharides, which will further contribute to the formation of effective LRS.
Keywords: nodule bacteria, Bradyrhizobium japonicum, soybean, legume-rhizobial symbiosis,
exopolysaccharides.

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