The aim of the work was to study the isoenzyme spectra of several lines of haploid regenerants of sugar beet in comparison with the parent forms in order to identify the most interesting ones for further selection. The donor material was the MS-form (malesterile form), haploid lines derived from it, as well as the fertile donor and its haploid lines.It was shown that the spectra of two enzymes − isocitrate dehydrogenase and malic enzyme are polymorphic, and the enzyme 6-phosphogluconate dehydrogenase is monomorphic and cannot be used in further selection.

Chemical fertilizers are a quick way to increase nutrients in the soil, but their use is economically costly and dangerous for the environment. Plant Growth Promoting Bacteria (PGPB) are able to increase the bioavailability of fertilizers through biological nitrogen (N) fixation, as well as potassium (K), phosphorus (P), and zinc (Zn) solubilization. The enhanced amount of soluble macro- and microelements in the close proximity of soil-root interface increases the fertilizer use efficiency ~ by 20-40 %.

One of the ways to maintain soil fertility is to use organic fertilizers. One of them can be straw of cereal crops (winter wheat and barley). However, the process of its decomposition can be delayed for several years. It is possible to accelerate the transformation process by using the native strain of cellulosolytic micromycete (Humicola fuscoatra VNIISS 016). Its introduction together with straw before plowing stabilizes agrophytocenosis. The experiments were carried out in laboratory under simulated conditions close to field ones. Scheme of the experiment: 1. Straw; 2. Straw + N (40 mg/4 g, which corresponds to 40 kg/ha); 3. Straw + N + H. fuscoatra + PC (nutritional supplement – molasses) (Kolesnikova M.V., 2014). As a result of the studies, it was established that winter wheat straw without additional components lost 0.86 g in weight (from the initial 4 g), 1.03 g when adding nitrogen fertilizer to the straw, and 1.49 g when using H. fuscoatra. We found that the addition of nitrogen to the straw stimulate the process of its transformation. Straw with nitrogen decompose faster than straw without any additives (by 41.5%). However, the addition of the native strain of micromycete accelerate the process by 48.3%. Barley straw lost 0.82 g in weight, straw with nitrogen fertilizer lost 1.06 g, straw and H. fuscoatra – 1.13 g. Further, the decomposition rate increased in the following row: straw → straw + N, where the speed was 26.7% higher → straw + N + H. fuscoatra, the decomposition rate is – 85.3% higher.

A large role in the creation of soil fertility and water-resistant structure, in the processes of humus synthesis and mineralization, as well as in the provision of agricultural plants with elements of mineral nutrition, belongs to soil microorganisms. For leached chernozem, the influence of field crops on the main groups of microorganisms, which are involved in the formation of effective and potential soil fertility, and associated enzymes was established. The purpose of the work is to study the effect of agricultural plants on the structure of the microbial community of the soil and the activity of enzymes involved in the formation of effective and potential soil fertility. Soil samples were taken from the 0-25 cm layer. They differed in anthropogenic load: virgin soil and soil where crops were cultivated. To count the number of soil microorganisms in the crops and their rhizospheres, we used the method of culturing successive dilutions of the soil suspension on selective nutrient media. The catalase activity of the soil was determined by the gasometric method. It is based on measuring the decay rate of hydrogen peroxide when it is interconnected with the soil in terms of the amount of oxygen released. The method for determining phosphatase activity is based on the quantitative calculation of inorganic phosphorus, which is formed by the breakdown of organic phosphorus compounds under the action of phosphatases.

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