Application of biological preparations based on bacteria and actinomycetes for plant protection

The active ingredient of the preparation is live cells and a complex of metabolites of the antagonist bacterium strain Bacillus subtilis M-22-VIZR. Gamair is intended for the protection of tomato against bacterial wilt, soft rot, and stem core necrosis. The biological preparation also shows activity against a number of phytopathogenic fungi (F. oxysporum, V. dahliae, V. solani, R. solani).

Recommended application rates and methods of use:

* seed treatment in a 0.025% solution of the preparation, * double spraying during the seedling stage, * spraying after planting the transplants in a permanent location at a concentration of 0.025% (application rate 9 kg/ha). 3.3.5. Preparations based on actinomycetes Alirin-S is recommended for the control of cucumber root rot. Alirin-S is compatible with other microbiological plant protection products (baktofit, phytolavin, alirin-B, gamair).

The protective action of the preparation consists in the ability of actinomycetes to multiply in the soil and inhibit the growth of phytopathogens, and to stimulate the growth processes of crops. The level of efficacy and spectrum of action are similar to those of Alirin-B.

Application features: three-time irrigation of plants with a 0.1-0.2% suspension of the biological preparation: at sowing, at transplanting to a permanent location, and at the beginning of flowering. Against powdery mildew, ascochyta blight, anthracnose, and alternaria blight, a three-time spraying is recommended during the growing season at intervals of eight to 20 days with a 0.2-1% solution at the very beginning of the epiphytotic development. Working solution consumption is from 1000 to 3000 l/ha. The producer strain belongs to the 4th hazard class, i.e., it is harmless to humans and warm-blooded LIVESTOCK.

Potential bacterial bioagents There are immense opportunities for the use of other, more effective, groups of microorganisms. Among them, bacteria belonging to associative diazotrophs are of extremely important practical value. These are bacteria that fix atmospheric nitrogen and live on the roots of non-leguminous host plants, entering into an associative symbiosis with them. Inhabiting the root surface and receiving necessary nutrients (sugars, organic acids, etc.) from the plant, diazotrophs, in turn, supply the plant with nitrogen through atmospheric fixation, which is especially important when there is an insufficient supply of this nutrient element. Currently, more than 200 species of diazotrophs are known, but only a small part of this diversity has been isolated from the root system of non-leguminous plants. The most frequent representatives are of the genera Azospirillum, Azotobacter, Klebsiella, Bacillus, and Pseudomonas.

Interest in associative diazotrophs is due to the fact that they can largely replace nitrogen from mineral fertilizers and guarantee against an excess of nitrate nitrogen in produce. But no less important is their ability to actively produce biologically active substances, the biosynthesis of which correlates with nitrogenase activity and the ability to fix nitrogen. In addition, these bacteria generally synthesize antibiotic compounds that suppress the growth and development of phytopathogenic microbiota.

It has been established that each vegetable crop corresponds to a specific number of nitrogen-fixing associations with high nitrogenase activity. Active nitrogen fixers have been isolated from the rhizoplane of cucumbers. Among diazotrophs, bacteria belonging to the genus Klebsiella dominate. Among the selected strains, one strain (Klebsiella planticola) stands out for a number of indicators and is currently being studied most thoroughly.

It is extremely interesting that even with the hydroponic method of plant cultivation (water culture), nitrogen fixers with high nitrogenase activity were also isolated from the rhizoplane of tomatoes.

Thus, there is a wide opportunity for using targeted associative symbiosis of vegetable crops with highly effective diazotrophs. This phenomenon can be used to improve the plant nutrition regime, in particular, by providing biological nitrogen and reducing mineral nitrogen application rates.

Fungal preparations Preparations of the Trichodermin series

In biological plant protection, the following species of the genus Trichoderma are used (according to Wat, 1969):

Phase 1. Initial interaction and host recognition. Parasitic strains of Trichoderma have a pronounced directional growth (chemotaxis) towards the hyphae of the host fungus. During growth, Trichoderma cells secrete exoenzymes which, by reacting with the cell walls of other fungi, are capable of destroying some of them. The resulting metabolites stimulate the directional growth of the Trichoderma mycelium.

Mechanisms of interaction of fungi of the genus

Phase 2. Physical and molecular interaction with the host. During this period, Trichoderma secretes a complex of antifungal substances, enzymes, and antibiotics.

Then the parasite twines around the hyphae of the host fungus, forms structures similar to appressoria, and perforates the cell wall. There are large strain differences in Trichoderma during this period:

• some of them are capable of attacking the host with antibiotics and enzymes before physical contact, and then colonizing dead cells;
• others require physical contact between their hyphae and the host mycelium to activate enzymes that destroy cell walls.