The Role of V-Strategist Endophytes in Stimulating the Formation of Mycorrhizal Interactions and Soil Regeneration

Abstract

Endophyte, new species of yeast fungus, which belongs to the genera Debariomycetaceae Vitasergia svidasoma Oliferchuk PRJNA807518 was isolated from the fruiting body of Tuber melanosporum VS1223 (IMB F-100106). The preparation Mykovital was created on its basis. The possibility of regulation of soil fertility was established through the influence on the “bacteria-fungus-plant” system by stimulation of mycorrhizal formation. By the introduction of seedlings and saplings of trees and shrubs of endophyte species in rhysosphere applying the preparation Mykovital at the different types of devastated soils. Environmental efficiency of biological recultivation of devastated lands is determined during the cultivation of forest crops, which is proved by their biological sustainability and morphological indicators. The research shows the possibility to systematize microorganisms according to the strategies of their survival in ecosystems in such a way, that besides К, r, and L strategists it is necessary to introduce another notion about another group of microorganisms in ecology and soil microbiology—endophytes which are proposed to be named as V-strategies. These are fungi endophytes that are capable to restore and stimulate mycorrhizal symbiosis in the “bacteria-fungus-plant” system and function as provision of “heterotrophic” nutrition of plants on the Earth. Based on the research, a conceptual model of recultivation of devastated lands was proposed and priority of soil ecosystem support services was established.

1. Introduction

The issue of increasing soil fertility is an ancient problem of human activity. These issues are also relevant in modern technologies of biological reclamation of devastated lands. Modern methods of growing forest crops and agricultural plants on these lands require specific approaches to increase the fertility of these soils. One of the approaches to increasing soil fertility is the method of stimulating mycorrhizal formation by influencing the “bacterium–fungus–plant” system through the introduction of an endophyte into the rhizosphere of the plant. The endophyte is introduced by using the drug “Mikovital.” The ecological expediency and economic efficiency of the use of the drug “Mikovital” have been proven.

2. Symbiotic existence of plants

Symbiosis is a phenomenon that is the basis of the existence of living organisms in nature. There is a scientific idea about autotrophic existence of vegetation. However, only in case of consideration of symbiotrophic existence of plants, that is, compulsory participation of microorganisms in essential processes of plant organisms, it is possible to solve unsolved issues of their vital living and understand a range of important mechanisms that sustain life on the Earth. Mycorrhizal fungi play a crucial role in regulating terrestrial carbon dioxide (CO₂) fluxes [1, 2, 3, 4]. They are obligate symbionts that form a relationship with plant roots known as mycorrhiza [5]. Mycorrhizal fungi obtain carbon from their host plants [6, 7] in exchange for the transfer of nutrients to the roots, which promotes plant growth. Previous studies have demonstrated the role of mycorrhiza in regulating plant productivity [8], water absorption [9, 10], litter decomposition [11, 12], root respiration [13, 14], soil respiration [15, 16, 17], stabilization of soil aggregates [18], and changes in soil carbon stocks [19], all of which affect above- and below-ground carbon dynamics in the ecosystem.

2.1 The role of “bacteria-: fungus- plant” system in providing life on the earth

The interaction of plants with microorganisms consists of a complex of complex processes that take place in two systems of different levels of organization: On the one hand, this is the microbial and fungal coenosis of the root zone of plants, and on the other hand, higher vascular plants, which are also interconnected in phytocenoses. As a result of such interaction, stable systems are formed, which play a key role in the functioning of natural edaphotopes and man-made agroecosystems.

The positive role of microorganisms in the root zone of plants is manifested in the transformation of organic residues, the synthesis of humus, the improvement of mineral nutrition of plants with nitrogen, phosphorus, and other macro- and microelements, the biocontrol of pathogens and pests, the production of biologically active substances that stimulate the growth and development of plants, and the detoxification of anthropogenic pollution. This ideal picture of positive interactions can be violated if the balance in the microbial-plant system is disturbed under the influence of natural or anthropogenic factors. In this connection, the tasks of correcting and regulating the functional structure and activity of microbial-plant systems arise.

One of the main ways of CO₂ input in the atmosphere is its emission from soils, or soil respiration, which is formed by root respiration and microbial decomposition of soil organic matter, dead plant residues, and organic substances produced by vegetative roots [20]. The sum of soil and above-ground respiration characterizes the gross respiration of the ecosystem, which, together with photosynthesis, forms the balance of CO₂ in the ecosystem, or net ecosystem exchange (Net Ecosystem Exchange, NEE). Therefore, the balance in the “plant-fungus-bacterium” system is of key importance for the deposition of carbon in the soil ecosystem and for maintaining the CO₂ balance in the atmosphere. The heterotrophic nutrition of plants has been studied quite widely for the last 150 years, and recent studies show that 98% of plants on Earth are mycotrophic, that is, those that live due to symbiosis with fungi and bacteria [5]. The ability to grow plants in sterile conditions, as well as in the conditions of the use of chemical means of protection and plant care, which have a detrimental effect on the soil microflora, for many years formed the opinion that the participation of microorganisms in the vital activity of plants is not mandatory, and only in recent decades scientists from many countries of the world thoroughly study mycorrhizal symbiosis and the functioning of the “bacterium-fungus-plant” system. The fallacy of such a judgment is caused by the fact that “sterile plants,” as well as plants treated with chemical agents, always have metabolic products of endophytes, epiphytes, and rhizosphere bacteria inside their seeds, and also contain endophyte cells themselves.

Thus, the role of mycorrhizal symbiosis in the functioning of Earth’s ecosystems can be represented by a diagram (Figure 1).

Figure 1.

The role of mycorrhizal symbiosis in functioning of the earth ecosystem.

Based on our vision, both autotrophic nutrition and heterotrophic nutrition of plants are provided by mycorrhiza, which is formed mainly on the roots of plants but can also be formed with other parts of it. Mycorrhizal symbiosis affects the functioning of the soil biota and is responsible for sustaining life on the Earth, the interaction of the geological with biological cycle of substances, regulation of the composition of the atmosphere and hydrosphere, regulation of the intensity of biosphere processes, the formation of humus, and provides a protection in relation to the lithosphere.

2.2 Factors contributing to the stimulation of heterotrophic nutrition of plants stimulate the formation of plant mycorrhizae

Bacteria contribute to the formation of mycorrhizal symbiosis. They are called helleras and stimulate the growth of fungi at the stage prior to symbiosis, increasing the probability of root contact with fungi. The study of bacteria and filamentous fungi living in plants has been widely studied and continues to be studied. The biology of another agent-stimulating mycorrhizal formation, namely endophytic yeasts, remains less clear [21]. Recent studies indicate the potential of endophytic yeasts for their use in industry and agriculture. Endophytic yeasts have significant advantages over bacterial and filamentous endophytes because they can be easily cultivated, stored for long periods of time, and introduced into crops [21].

The use of endophytic yeasts is an effective way to reduce fertilizer and water use in agriculture and potentially increase yields. Their application is particularly promising in the field of heavy metal pollution remediation, and as biocontrol and bioregulatory agents to protect plants from pathogens.

A number of authors describe the great variability of endophytic yeast communities based on the plant host, as well as the influence of various biotic and abiotic factors that influence the composition of these communities. The authors express the opinion that among endophytic yeasts, ascomycetes mainly dominate [22].

Our studies agree with the studies of a number of authors and testify to the positive influence of a new species of endophyte belonging to the Debariomycetaceae family, the ascomycete Vitasergia svidasoma PRJNA807518, on the composition of soil mycobiota and plant productivity [23, 24, 25].

Most of the knowledge about the plant growth-promoting properties of endophytes is derived from the study of bacterial endophytes, as they have been studied in common ecological niches with yeast fungi in the phytosphere. In addition, there is an evidence of the formation of a mixed biofilm containing both bacteria and yeast [26, 27].

Several growth-promoting properties of endophytic yeasts include phytohormone production, stress relief, pathogen protection, and increased plant nutrient uptake. This action is caused by the production of IAA, the production of siderophores, and the activity of ACC deaminase.

The production of plant hormones provides a direct way to stimulate plant growth by endophytes. Auxins and gibberellins have many plant growth-promoting properties, including promoting root growth and stem elongation, as well as cell proliferation and elongation. In particular, a number of authors indicate the production of indole-3-acetic acid (IAA) by endophytic yeast [28, 29, 30].

One of the characteristics of endophytic yeast is the promotion of plant tolerance to stress [31]. In addition, endophytic yeasts produce polyamines, compounds that play an important role in plant growth and are involved in many cellular processes, including the synthesis of macromolecules, as well as cell growth, survival, and stress resistance. Yeast can also generally promote plant growth [32].

2.3 Industrial and ecological use of endophytic yeasts

Given the plant growth-stimulating properties of endophytic yeasts, they can be widely used in agriculture. The production of indole-acetic acid, a phytohormone that stimulates plant growth, by three yeast strains is described. To the best of our knowledge, the yeast strains presented in this study were the first endophytic yeast strains isolated from Populus species [33]. In addition, another strain of Rhodotorula was shown to increase germination of cucumber seedlings both by inoculation and by treatment with filtered supernatant [34]. The authors emphasize that the use of these yeast endophytes in agriculture can reduce water and fertilizer consumption, and it is important to study them in the future, given the growing population and increased demand for food.

There are also data that endophytic yeasts can be used for bioaugmented phytoremediation of heavy metals, as using only plants for this process affects their growth and often harms the plants. The use of endophytic yeast showed that seedlings of Brassica sp. treated with the endophyte Rhodotorula sp. showed enhanced growth and increased transformation of Cd, Pb, Zn, and Cu [35].

Another promising direction of the use of endophytic yeasts in agriculture is their use as biocontrol. The described strain of Rhodotorula rubra, isolated from rice, showed strong suppression of various types of pathogens and toxin-producing species of Fusarium [34]. Antifungal activity of poplar endophyte Rhodotorula graminis against common fungal pathogen Rhizoctonia solani is also known [36].

Endophytic yeasts can be used for the metabolism of various chemicals that are difficult to produce because they possess a significant range of metabolic processes and are characterized by a wide range of tolerance to environmental conditions [28].

An important characteristic of endophytic yeast is the ability to colonize the host plant. The endophytic yeast R. graminis is able to colonize the entire plant, including leaf and xylem tissue, when the plant is inoculated from the roots [36]. The yeast can colonize the plant passively by simply growing inside the root until the population gains access to the xylem tissue and from there colonize the rest of the plant with the flow of water that passes through the plant. Like fungi and bacteria, endophytic yeasts have the enzymatic ability to destroy plant cell walls [37, 38, 39].

2.4 The role of endophytic yeast V-strategists Vitasergia svidasoma PRJNA807518 in stimulating the productivity of forest crops

In 2002, we isolated an endophyte from the fruiting body of the Perigord truffle, which was identified as a new yeast species Vitasergia svidasoma PRJNA807518 [23]. Based on the isolated endophyte, the preparation “Mykovital” was created, which received state registration, the Organic Standard certificate, and all the necessary ecological and technical documentation, which made it possible to use it in the studied areas of forests, fields, and pomological gardens of Ukraine [24, 25].

2.5 Features of tuber melanosporum ascomycetes and yeasts symbiotic with them

Truffles are one of the most famous ectomycorrhizal fungi in the world. There is little information on the ecological mechanisms of ectomycorrhizal synthesis of truffles in vitro. Truffles are filamentous fungi belonging to the genus Tuber, found naturally in various climate zones of the Northern Hemisphere. Some truffle species, such as the Perigord black truffle (T. melanosporum) and the white truffle (T. magnatum), are found in Europe, the Chinese black truffle (T. indicum)—in Asia, and the Peking truffle (T. lyonii)—in North America, especially known for the organoleptic qualities of their fruiting bodies and are among the most expensive culinary delicacies in the world.

The Tuber melanosporum genome contains only 7500 protein-coding genes, with very rare polygenic families. The structural organization of the genome of T. melanosporum is strikingly different from other ascomycetes. It lacks large sets of carbohydrate-degrading enzymes, but some of them are involved in the degradation of plant cell walls during colonization.

Black truffle is characterized by extremely low allergenicity, as well as the absence of mycotoxin synthesis enzymes, and the overexpression of various flavor-related enzymes in the fruiting body. Among the latter, processes of sulfur assimilation and enzymes of interconversion of S-amino acids are active. These include by-products of methyl sulfide volatiles found in truffles and enzymes involved in the breakdown of amino acids via the Ehrlich Pathway, which produces the well-known truffle volatiles and flavors, such as 2-methyl-1-butanal.

Another feature of truffle-fruiting bodies is their symbiosis with yeasts. A total of 29 yeast strains isolated from ascocarps of black and white truffles (Tuber melanosporum Vitt. and Tuber magnatum Pico, respectively) are described. The strains were identified as Candida saitoana, Debaryomyces hansenii, Cryptococcus sp., Rhodotorula mucilaginosa, and Trichosporon moniliiforme [40].

Scientists attribute the complex aroma of truffles to the additional role of yeast symbionts, which share similar characteristics as the ecosystem of the fruiting body.

Volatile organic compounds (VOCs) released by fruiting bodies belong to several chemical classes (aldehydes, alcohols, esters, lactones, terpenes, and sulfur compounds). Truffle ascocarps are interesting ecological niches because they form a symbiosis with the root systems of various tree species.

Some yeast strains, such as Cryptococcus humicolus, which are constantly present on the surface of mature truffles, have shown extracellular cellulolytic, chitinolytic, and proteolytic activities that may promote ascocarp growth and nutrition during the saprophytic stage, or promote fungal ascospore dispersal [41].

2.6 The effect of the preparation “Mykovital” on the growth and development of seedlings of trees and shrubs

The new yeast species Vitasergia svidasoma PRJNA807518, which is the active agent of the Mykovital preparation, is widely used to stimulate the mycorrhizal formation and plant productivity. An experiment on growing planting material was conducted in a semi-controlled environment. Seedlings of trees and shrubs common in phytoremediation were used: Quercus robur L., Pinus sylvestris L., Betula pendula Roth., Sorbus aucuparia L., Prunus divari-cata Ledeb., Robinia pseudoacacia L., Hippophea rhamnoides L., and Rosa canina L. During the experiment, treatment of plant roots with Mykovital was used. Seedlings planted without treatment served as a control.

The ameliorative role of the inoculation of tree and shrub seedlings on sulfur-containing man-made soils of the Yavoriv sulfur quarry was investigated during two growing seasons in semi-productive conditions by planting seedlings in boxes with soil selected from embryonic soils. Seedlings care and measurement of their morphometric indicators of growth and development were carried out throughout the growing season. The growth and development of the planted seedlings were evaluated by the viability of the plants and their growth in height during the first and second years of cultivation.

The results of a two-year experiment on the cultivation of experimental plants in two versions, treated and untreated with the preparation Mykovital, are summarized in Table 1.

Name of species	Untreated root		Treated root
	Years of observation		Years of observation
	2019	2020	2019	2020
Common oak	21	21	85	88
Scots pine	35	37	89	86
White acacia	39	27	94	96
Betula pendula	36	38	96	96
Prunus cerasifera (cherry plum)	34	32	88	98
Sorbus aucuparia	34	35	79	87
Sea-buckthorn	26	27	74	89
Dog rose	25	25	88	89

Table 1.

Survival of planting material with treatment of plant roots with the preparation Mykovital, and without treatment, %.

The survival rate of seedlings of experimental breeds is on average 31.25 ± 2.00% in 2019 and 30.25 ± 1.80% in 2020. Treatment of seedlings with Mykovital contributes to a significant increase in their survival rate. Thus, in 2019, the average rate of survival of experimental breeds was 85.37 ± 4.56% and 91.12 ± 3.54% in 2020. That is, the increase in survival of seedlings of experimental breeds in 2019 was an average of 2.7 times, and in 2020 3.0 times more compared to the control (not treated with Mykovital). At the same time, it should be pointed out that the survival rate varied both within a single breed and in a separate growing season (Table 2). In both, the first and second growing seasons, the highest survival rate was observed for common oak seedlings—4.04 and 4.1 times more, respectively. The highest rate of survival of pine was 2.5 times in 2019 and 2.3 times in 2020. Dog rose, acacia, and other plants actively survived.

Name of species of seedlings	Ratio of treated/untreated
	2019 year	2020 year
Common oak	4.04	4.1
Scots pine	2.5	2.3
White acacia	2.4	3.5
Betula pendula	2.6	2.5
Prunus cerasifera (cherry plum)	2.5	3.0
Sorbus aucuparia	2.3	2.4
Sea-buckthorn	2.8	3.2
Dog rose	3.5	3.6

Table 2.

The survival rate of fitomeliorating cultures treated and untreated with the preparation Mykovital, times.

The obtained results confirm the effectiveness of the method of improving the survival and growth of seedlings when treated with Mykovital, which significantly activates the processes of survival and growth of tree and shrub seedlings on technologically polluted and degraded soils of the sulfur quarry. Patents have been issued for this method.

In addition, to determine the effect of treatment with the preparation Mykovital on the survival of forest crops, the study of the effect of treatment with the preparation of endophyte—a stimulator of mycorrhizal formation on the growth of seedlings in height was given. The results of measuring observations are summarized in Table 3.

Name of species of seedlings	Growth in height, cm				Growth of treated/growth of untreated, times
	Untreated		Treated
	Zh ± m	p., 95%	Zh ± m	p., 95%
Common oak	4.19 ± 0.18	0.37	10.64 ± 0.23	0.48	2.5
Scots pine	5.02 ± 0.16	0.32	10.33 ± 0.19	0.38	2.1
White acacia	10.71 ± 0.15	0.31	31.81 ± 0.42	0.87	3.0
Betula pendula	13.38 ± 0.50	1.04	34.40 ± 0.65	1.35	2.6
Prunus cerasifera (cherry plum)	6.76 ± 0.23	0.48	22.41 ± 0.21	0.44	3.3
Sorbus aucuparia	7.87 ± 0.22	0.46	23.29 ± 0.25	0.52	3.0
Sea-buckthorn	5.99 ± 0.21	0.44	14.62 ± 0.20	0.42	2.4
Dog rose	4.69 ± 0.21	0.44	14.54 ± 0.25	0.52	3.1

Table 3.

The preparation Mykovital treatment effect on the growth of seedlings.

According to the results of observations, a positive effect of the treatment of seedlings with the preparation Mykovital was established (at a high level of accuracy (p 95% < 1.35%). The increase in the height of the studied species reached an average of 2.7 times compared to the control. In terms of species, as well as survival, and the difference is also observed in the growth of seedlings in height. The main reason may be the genetic condition of a specific species regarding the rate of formation of mycorrhizal symbiosis, which depends on the work of signaling mechanisms in the “plant-fungus-bacterium” system.

Thus, the growth of pine seedlings increased by 2.1 times, sea buckthorn by 2.5 times, oak by 2.5 times, birch by 2.6 times, rowan by 3.0 times, Robinia pseudoacacia by 3, 0 times, dog rose −3.1 times, and plum seedlings –3.3 times. The increase in height of seedlings treated with mycorrhiza is two to three times higher than the control. At the same time, it was established that deciduous species respond more actively to the application of the spore preparation of mycorrhizae compared to Scots pine. Shrub species and the introducer, Robinia pseudoacacia react, most intensively to the treatment of the root system of Vitasergia svidasoma PRJNA807518 seedlings.

Similar data were obtained in the characteristics of seedling growth in height in the first growing year after transplanting (Table 4).

Name of species of seedlings	Height of the plant, cm
	Untreated		Treated
	H ± m	p., 95%	H ± m	p., 95%
Common oak	13.76 ± 0.20	0.37	20.44 ± 0.25	0.48
Scots pine	15.64 ± 0.16	0.33	21.22 ± 0.16	0.34
White acacia	31.07 ± 0.14	0.33	52.44 ± 0.39	0.79
Betula pendula	32.95 ± 0.47	0.98	54.18 ± 0.60	1.24
Prunus cerasifera (cherry plum)	22.41 ± 0.16	0.34	37.90 ± 0.15	0.32
Sorbus aucuparia	25.08 ± 0.16	0.32	40.58 ± 0.19	0.39
Sea-buckthorn	20.62 ± 0.16	0.33	29.52 ± 0.19	0.40
Dog rose	14.66 ± 0.15	0.31	24.76 ± 0.20	0.41

Table 4.

The height of planting material of meliorative species treated and untreated with the preparation Mykovital, cm.

According to Table 4, it can be seen that the average height of the seedlings of all studied breeds increased by 55.77% compared to the control. And within the boundaries of specific species, the height of seedlings reaches the following values: seedlings of Scots pine by 35.70%, sea buckthorn by 43.11%, oak by 48.55%, birch by 61.76%, rowan by 64%, 43%, pseudoacacia Robinia by 68.78%, dog rose by 68.97%, and plum seedlings by 69.12%.

The given data testify to the positive effect of mycorrhizal symbiosis on the growth and productivity of plants in the conditions of man-made soils polluted with sulfur. According to the research results, the promising use of the preparation for stimulating mycorrhizal processes Mykovital with the active agent—Vitasergia svidasoma PRJNA807518 in the amount of cell titer 7x109 to increase the resistance of seedlings and saplings of trees and shrubs to the adverse factors of sulfur pollution of the soil has been established.

2.7 The influence of the preparation Mykovital on the chemical composition of plants

Mycorrhiza causes the maximum influence on the vitality of the host plant, exactly where it reaches the greatest development. Since the statistical survival of seedlings was low on the lands disturbed by sulfur mining due to the lack of mycorrhizal formation and nutrients necessary for growth, we compared them with artificially mycorrhized seedlings. When examining the root systems of uninfected seedlings that took root in cultures on embryos, mycorrhiza was found. The rest of the uninfected showed signs of a lack of nutrients, characteristic of nitrogen and phosphorus starvation, and a lack of trace elements. The mycorrhized plants differed not only in a better appearance, greater height, and weight, but also had twice as many short roots.

Thus, the surface area of the root system of the plant increases, which gives it the possibility of effective nutrition (Table 5).

Indicator	Seedlings		Reliability of experiment
	Treated	Untreated
Raw weight, mg	1242	598	Р > 0.01
Absolute dry weight, mg	345	155	Р > 0.01
Nitrogen, % to absolute dry weight	1.78	1.88	Р > 0.01
Nitrogen in single seedling, mg	5.75	2.87	Р > 0.01
Phosphorus, % to absolute dry weight	0.185	0.097	Р > 0.01
Phosphorus in a single seedling, mg	0.60	0.15	Р > 0.01
Potassium, % to absolute dry weight	0.66	0.62	Р > 0.01
Potassium in a single seedling, mg	2.17	0.96	Р >0.01

Table 5.

Chemical composition of scots pine seedlings treated and untreated with the preparation Mykovital.

The results of the chemical analysis showed that the seedlings treated with Mykovital contain significantly more nitrogen, phosphorus, and potassium than in non-mycorrhizal plants, and the difference is well observed in absolute dry weight.

In addition, the content of nitrogen, phosphorus, and potassium in seedlings during the season was determined. The results are summarized in Table 6.

Indicators	05.07.2019		20.08.2020
	Treated	Untreated	Treated	Untreated
Short mycorrhiza roots, %	68.6	1.2	70.2	9.5
Absolute dry weight of plant, mg	207.9	160.2	337.2	180.6
Absolute dry weight of root, mg	72.3	73.0	127.4	74.6
Absolute dry weight of sampling, mg	135.6	87.2	209.8	106.0
Ratio of absolute dry weight of roots to samplings	0.53	0.84	0.61	0.71
Nitrogen, % to absolute dry weight	1.49	1.23	1.60	1.20
Nitrogen in single seedling, mg	3.1	2.0	5.4	2.2
Phosphorus, % to absolute dry weight	0.13	0.08	0.21	0.07
Phosphorus in a single seedling, mg	0.27	0.13	0.72	0.13
Potassium, % to absolute dry weight	0.45	0.55	0.63	0.45
Potassium in a single seedling, mg	1.03	0.88	2.12	0.81

Table 6.

Chemical composition of scots pine seedlings treated and untreated with the preparation Mykovital.

It was established that mycorrhized seedlings accumulate a much larger amount of mineral nutrients in terms of the absolute dry weight of plants (Table 6).

The main nutrients such as nitrogen, phosphorus, and potassium were in low concentrations in non-mycorrhizal seedlings, while the absolute and percentage content of these nutrients increased in seedlings treated with mycorrhizal preparation. Over time, plants that were not treated with a stimulator of mycorrhizal formation began to show symptoms of starvation and died, while mycorrhizal ones continued to grow.

The given information indicates that the use of the proposed methods of biological restoration and improvement of survival of plants during afforestation of devastated lands ensures higher survival and growth of forest crops contributes to effective biological restoration of devastated lands due to stimulation of mycorrhizal formation, formation of plant cover, and rhizosphere remediation of the territory.

2.8 Recovery of the “bacterium-fungus-plant” system with the participation of the stimulator of mycorrhizal formation—the fungus Vitasergia svidasoma PRJNA807518

The conceptual model of the use of the proposed biological method on various types of devastated lands includes the use of natural self-recovery of the soil and plant cover and optimization of the soil environment by improving the properties of the soil system, biodetoxification, and biodecontamination through the expansion of populations of soil microorganisms and the use of phytomeliorants with a simultaneous effect on the biological and inorganic components of the soil.

The disadvantages of the proposed methods are that the genetic material of microorganisms (bacteria and fungi) is introduced into the ecosystem without a preliminary study of the micro- and mycoflora of these soils. Usually, the introduction of a living biological preparation is aimed at solving a local problem, for example, to stop the development of pathogenic microorganisms or toxin-producing microorganisms; besides, there are no data on the ability of microorganisms to adapt to different types of devastated soils and their contamination with toxic substances and their effectiveness. In the theory and practice of such influence on the soil ecosystem, there is the term “biocontrol,” which fully corresponds to the content, since control over pathogens and toxin-producing agents occurs due to changes in chemical and biochemical interactions with the environment and due to natural antagonism between species and their metabolites. However, this does not consider how other groups of microorganisms react to such actions, such as K-strategists. This is a group of bacteria and fungi that are able to maintain a stable population level in climactic systems when soil conditions are relatively stable and stress reactions are absent. These microorganisms fully and economically consume external resources and provide themselves with a stably high population density. The impact of separately introduced strains on r-strategists is also important, which develops in the soil when a large amount of readily available substrates are received and have a high growth rate, due to which there are outbreaks of an increase in the number of populations that quickly assimilate the substrate. They develop with particular activity at the initial stages of successions during the settlement of some substrate, for example, during the assimilation of harvest residues or during the degradation of wood during the formation of forest plantations. Although the membership of fungi or bacteria to a certain strategy is not absolute, because each species has the ability to assimilate substrates and can withstand certain stressful situations, it is still necessary to carry out the distribution of microorganisms according to strategies in relation to each individual microbial group in a certain ecological situation, which was done by us while studying the structure of soil micromycetes of different degrees of degradation of forest soils and agrocenoses.

We did not focus our attention on “biocontrol” but studied the integral system “plant-fungus-bacterium” and methods of its bioregulation, which involves, in our case, the introduction of an endophyte into the soil ecosystem through the rhizosphere of the plant, which triggers self-recovery and self-regulation mechanisms in microecosystems and is, in a way, a “catalyst” of natural processes that restore the natural mycorrhizal triple symbiosis and the general mycorrhizal network in the ecosystem. We showed the efficiency and productivity of this process by using and testing a species new to science, belonging to the Debariomycetaceae family—the endophyte Vitasergia svidasoma PRJNA807518, isolated from the fruiting body of black truffle, which, in fact, stimulates the processes of mycorrhizal formation.

Back in 1966, the famous American ecologist Barry Commoner outlined modern environmental problems in the form of certain aphorisms as well-known laws. One of his laws is “Nature knows best.” This law prompts us to the need for reasonable regulation by already existing principles in natural ecosystems. We only need a systematic process of deep knowledge and understanding of the functioning of these complex systems and the search for new mechanisms and discoveries in their reasonable management.

Our research indicates that mycorrhizal associations are key in the plant-fungus-bacterium triple symbiosis. In spring, when the vegetation process begins, the plant releases exudates into the rhizosphere, the basis of which are sugars. At the same time, the endophyte fungus with which the plant is inoculated, according to the technology, affects the species composition of microbial-fungal associations and stimulates the processes of their functioning. Effective growth and development of mycorrhizal associations begin. Mycorrhizal fungi secrete trehalose into the medium, a disaccharide that is synthesized in the cells of many fungi and enters the environment of the mycorrhizosphere and rhizosphere of plants as part of mycelial exudates. It is believed that trehalose is one of the factors that determine the composition of bacterial communities. All life forms on the Earth—the transfer of inorganic substances within and between different carbon reservoirs is the basis of all organic substances and the source of hydrocarbons for plants. An effective process of photosynthesis can occur only with a sufficient amount of carbon. For this, plants need 50% of carbon and only 5–7% of minerals, including macroelements (phosphorus, nitrogen, and potassium) and microelements (cobalt, zinc, magnesium, iodine, and iron).

The result of the tested approach ensures the adaptation of trees to the soils of devastated lands by influencing the formation of plant associations with an effective plant metagenome and mycorrhizal formation due to the regulatory mechanisms of Vitasergia svidasoma PRJNA807518 resistant to the environmental conditions that occur on lands in need of restoration.

The implementation of the method involves the performance of the biological stage of the work that is, on the prepared area, planting deciduous and coniferous trees, the roots of which are treated with the mycorrhizal preparation Mykovital.

2.9 Conceptual model of restoration of disturbed lands

Restoration of biological properties of devastated soils and optimization of its biochemical processes is related to restoration of chemical and physical parameters of the soil, which requires the use of an appropriate system of agrotechnical measures. The use of V-strategies to restore and create a mycorrhizal network in the ecosystem will contribute to the stimulation of signaling systems between the plant, fungus, and bacteria, especially at the initial stages of restoration of degraded soils, will ensure higher resistance of plants to natural and man-made stresses, and increase their productivity. Achieving compliance of the state characteristics of the restored area with regulatory requirements is recognized as a successful result of the measures (Figure 2).

Figure 2.

Conceptual model of restoration of disturbed lands.

The conducted research gives reason to conclude that, in forest biocenoses, the proposed biotechnology will give an opportunity to influence the formation of tree stands, and, in agroecosystems, it will be possible to create self-regulating phytocenoses. The viability of forest crops, their growth, and development contribute to the faster closing of forest meliorative crops (at least for 1 year) and the reduction of the cost of crops production and care. The proposed approach of biological restoration is ecologically feasible and economically justified and has remarkable social significance.

The developed and proposed preparation provides accelerated growth and development of plants due to activation of soil microflora, and improvement of nitrogen and phosphorus nutrition. The application of this method of restoration not only accelerates the process of soil formation, but also improves the ecological conditions in the area of application: It contributes to the creation of a green landscape, the improvement of the air environment, and the return of disturbed lands to land use.

The conducted experiments made it possible to verify the possibility of creating cultural phytocenoses with minimal costs for improving the properties of the substrate.

The restoration of various types of devastated soils, the use of natural self-healing of the soil and plant cover, and the optimization of the soil environment by improving the properties of the soil system, biodetoxification, and biodecontamination through the stimulation of symbionts—endophytes, and the creation of a general mycorrhizal network in the ecosystem are a promising dynamic direction in land use.

3. Conclusions

• The possibility of regulating soil fertility through the influence on the “bacterium-fungus-plant” system by stimulating mycorrhizal formation through the introduction of an endophyte species into the rhizosphere of the plant through the use of the preparation “Mykovital” on various types of devastated soils has been established;

• The ecological effectiveness of biological restoration of devastated lands during the cultivation of forest crops and agricultural plants with the use of the preparation “Mykovital” was confirmed by their biological stability and morphophysiological indicators, and an increase in the productivity of tree and shrub seedlings was established;

• A conceptual model for the restoration of devastated lands based on endophytes V-strategists is proposed;

• A shift in the paradigm of thinking in regard to the priority of autotrophic nutrition of plants is proposed and the equivalence of “heterotrophic” nutrition of plants and the role of mycorrhizal symbiosis in the functioning of the Earth’s ecosystem is indicated.