# Fungi of the _Trichoderma_ Genus: Future Perspectives of Benefits in Sustainable Agriculture
## 4 Application of _Trichoderma_ Fungi in the Control of Fungal Plant Pathogens
### Competition for Nutrients and Space  
Fungi of the genus _Trichoderma_ can quickly grow and colonize culture media as well as the rhizosphere and spermosphere, e.g., of soybean, maize, tomato, and lettuce, which also leads to the limitation or complete inhibition of the development of plant pathogens [103; 104; 105; 106]. In the soil environment, this process is closely related to the ability of microorganisms to form a biofilm. _Trichoderma_ sp. secrete extracellular polymeric sub stances, which leads to the formation of extensive aggregates based on soil-fungal exudate cells on the surface of roots or soil [87]. A study by [PERSON] and [PERSON] [107] showed that _T. harzianum_ competed for space and nutrients with _F. culmorum_. Based on a macroscopic analysis of Petri dishes on which the antagonist and pathogen biculture was formed, it was found that _Trichoderma_ sp. colonized the available surface much faster than _Fusarium_ at 15 \({}^{\circ}\)C and 25 \({}^{\circ}\)C. Similarly, [PERSON] and [PERSON] [108] observed that T. harzianum inhibited the growth of _A. alternata_, _A. infectoria_, and _F. acuminatum_. The authors documented that the growth rate of the antagonist mycelia in biculture was 3.4-4 cm/day, while for the pathogens, the growth rate was in the range of 0.8-1.2 cm/day. [PERSON] et al. [109] demonstrated that _Trichoderma_ fungi inhibited the development of _A. solani_ under in vitro conditions. The results of the analyses indicated that the colony diameter of the pathogen in the control sample was 82.66 mm, while in the bicultures, the diameters of _A. solani_ were 30.6 mm, 27.3 mm, and 23.3 mm for _T. atroviride_, _T. harzianum_, and _T. longibrachiatum_, respectively. [PERSON] and [PERSON] [110] proved that _T. hamatum_, _T. harzianum_, _T. kontigii_, _T. longibrachiatum_, _T. pililiferum_, and _T. viride_ reduced the growth of _F. oxysporum_ on a PDA medium by an average of 64.8-77.2%. In turn, [PERSON] et al. [111] reported that _T. atroviride_, _T. viride_, and _T. viridescens_ inhibited the development of _F. cerevisiae_ and _F. culmorum_ by 24-66%. _Trichoderma_ species colonized 75-100% of the medium surface. According to [PERSON] et al. [112] and [PERSON] and [PERSON] [113], the most common cause of the death of pathogenic microorganisms is competition for nutrients that are present in limited amounts in the medium. Compared to other fungi, _Trichoderma_ sp. has a much greater capacity to absorb nutrients from the substrate and from the soil than other microorganisms [63; 114]. This feature is related to the production of a wide range of organic acids (gluconic acid, citric acid, fumaric acid) by these fungi, which lower the pH of the soil and thus increase the solubility and absorption of the minerals present in the ground, including phosphates [32; 55]. Acidification of the substrate disrupts the equilibrium, leading to the elimination of microorganisms that are unable to survive in the new environmental conditions. _Trichoderma_ sp. also gains an advantage over pathogens in nutrient extraction, owing to its high ability to absorb energy from many different types of sugars that are a part of root secretions. This energy, stored in the form of ATP, allows these fungi to efficiently and quickly extract nutrients from the soil [21; 112]. According to studies by [PERSON] et al. [115], the production of siderophores by _Trichoderma_ sp. depends on the pH of the substrate. The authors tested three pH ranges (4.5-6.5) in in vitro tests and observed the strongest production of siderophores in the medium with the lowest pH (4.5). In contrast, [PERSON] et al. [116] found that the optimal pH for siderophore production is maintained at the neutral level. One of the microelements necessary for the growth and proper functioning of many microorganisms are iron ions [87]. In alkaline soils and under aerobic conditions, these ions form insoluble and difficult-to-absorb iron oxides.