Controlled breeding of the psychrophilic strain G-034 VIZR of Trichoderma asperellum for fast crop residues’ polymers utilization and soil enhancement
Genus Trichoderma strains as the natural plant residues' biodestructors, highly active antagonists of soil phytopathogens and phytoregulators with the widest range of optimum conditions for their development, are widely used in biologics development. Of particular importance in Russia's northern regions, especially in winter crop cultivation, is the ability of a microorganism's strain used in agro-technologies to maintain viability and target biological activity at low temperatures. In this connection, this work purpose is to select a psychrotolerant strain of T. asperellum for the rapid crop residues' polymer utilization and soil enhancement at low temperature, as well as to evaluate its activity under laboratory and field conditions. In the work process, the following tasks were addressed: selecting psychrotolerant strains of T. asperellum with high cellulolytic activity; further controlled breeding of psychrophilic strains capable of rapid growth, active colonization of plant substrates and high sporulation at 4-8 °C; evaluating the target activity of the selected psychrophilic strain as a cellulolytic as well as antagonistic activity against cereal pathogens; obtaining laboratory samples of bioformulations by deep-surface cultivation on non-sterile peat and multirecycled wastes from the edible mushrooms production and assessing their efficacy in field small-plot trials. The methods for inoculum cultivation, sporulation capacity determination, modified wet chamber, estimating antagonistic activity and biologics' quality, field small-plot trials management, quantitative estimates of biomass losses, cellulose and lignin content were used in the work. The active psychrophilic strain for the rapid crop residues' polymer utilization and soil enhancement controlled breeding was selected during a four-step screening of 29 T. asperellum strains from All-Russian Research Institute of Plant Protection (VIZR) State Microorganisms' Collection with high cellulolytic and antagonistic activities. In terms of linear growth rate, antagonistic and hyperparasitic activities at 4-8 °С, a high rate of wheat and maize stubble residues' colonization, a perspective psychrophilic strain G-034 of T. asperellum was selected for developing the laboratory samples of biologics and for running field trials. In small-plot trials, the active maize crop residues' decomposition under the T. asperellum G-034 influence was revealed, resulting in the complete loss of plant intact state in 12 months due to more than 80 % cellulose and 20 % lignin biodestruction. The maximum loss of maize crop residues biomass for 12 months was more than 70 %. The T. asperellum strain G-034 was active after field hibernation in an amount of x10<sup>4</sup> cfu/g, resulting in a titer increase with seasonal temperature rising and the trophic base bioavailability growth.