Antibacterial Activity of Different Strains of the Genus Trichoderma

Abstract

The main pathogens causing plant diseases are bacteria, viruses, and fungi. A number of strategies are usually used for plant protection and control of pathogenic microorganisms. The main interest of researchers is focused on the development of alternative synthetic chemicals to control bacterial diseases of plants. Among such approaches, biological control of bacterial diseases using agents such as antagonistic fungi and some other microorganisms is considered to be one of the most effective strategies. Species of the genus Trichoderma are known for their antagonistic activity against plant pathogenic fungi and bacteria and can be an effective safety strategy to control them. An important peculiarity of fungi of this genus is their ability to inhibit target pathogenic organisms without harming non-target (beneficial) microorganisms. The study of the antagonistic activity of fungi of the genus Trichoderma was conducted mainly against pathogenic fungi of agricultural plants. At the same time, the study of the antibacterial activity of fungi of this genus has attracted much less attention. Therefore, the aim of our work was to determine the antibacterial activity of microscopic fungi of the genus Trichoderma against test cultures of bacteria causing pathogenesis of agricultural plants. Methods. The objects of research were 100 fungal strains of the genus Trichoderma and six economically important plant pathogenic bacteria such as Pseudomonas syringae UCM В-1027Т, Pseudomonas fluorescens 8573, Pectobacterium carotovorum UCM В-1095T, Xanthomonas campestris pv. campestris UCM В-1049, Clavibacter michiganensis subsp. michiganensis 102, and Agrobacterium tumefaciens UCM В-1000. Cultures of the studied fungi were grown on potato-dextrose agar. The antagonistic activity of fungi of the genus Trichoderma against plant pathogenic bacteria was studied using the conventional method of diffusion in agar and method of dual culture. The antibacterial activity of culture filtrates of Trichoderma strains was evaluated via the zone of growth inhibition of plant pathogenic bacteria. The percentages of growth inhibition of plant pathogenic bacteria were calculated, and the antagonistic activity of strains was concluded on the basis of the obtained values. Results. In general, the studied Trichoderma strains had the antagonistic activity against plant pathogenic bacteria. Using method of diffusion in agar, it was shown that among the 100 studied Trichoderma strains, 12 had the effect of growth inhibition (bacteriostatic effect) of all six studied species of pathogenic bacteria; 20 strains inhibited the growth of five ones, 36 — four, 12 — three, and 7 — of two strains. The strains with a wide spectrum of antibacterial activity were studied by the double culture method. This made it possible to demonstrate the high selectivity of the antagonistic effect of Trichoderma strains on individual test cultures of phytopathogenic bacteria. For example, strain No7A inhibited the growth of C. michiganensis subsp. michiganensis 102 by 47% and the growth of P. syringae UCM B-1027T by 30%, while the zones of growth inhibition of these test cultures, determined by the method of diffusion in agar, were 5 and 6 mm, respectively. Conclusions. The obtained results indicated the potential and overall ability of Trichoderma strains to biologically control bacterial pathogens. The most promising for the use of plant pathogenic bacteria as agents for biocontrol were strains F-60, 1515, and 320, which were active against all studied bacteria. Such strains may have the potential as a preventive biocontrol agent of plant pathogens with a wide range of action. On the other hand, Trichoderma strains with high activity against certain pathogens may have the potential to be used as a control agent against a specific target pathogen.