The Role of Cell Wall Degrading Enzymes in Antagonistic Traits of Trichoderma virens Against Rhizoctonia solani

Background: High antagonistic ability of different Trichoderma species against a diverse range of plant pathogenic fungi has led them to be used as a biological fungicide in agriculture. They can also promote plant growth, fertility, resistance to stress, and absorption of nutrients. They are also opportunistic and symbiotic pathogens, which can lead to the activation of plant defense mechanisms. Objectives: The aim of this present study was to investigate possible enhancement of lytic enzymes production and biocontrol activity of T. virens against Rhizoctonia solani through gamma radiation and to find the relationship between changes in lytic enzyme production and antagonistic activity of T. virens. Material and Methods: Dual culture conditions were used to evaluate the antagonistic effect of T. virens and its gamma mutants against R. solani. Then, their chitinase and cellulase activities were measured. For more detailed investigation of enzymes, densitometry pattern of the proteins was extracted from the T. virens wild-type and its mutants were obtained via SDS-polyacrylamide gel electrophoresis. Results: The mutant T.vi M8, T. virens wild-type and mutant T.vi M20 strains showed the maximum antagonistic effects against the pathogen, respectively. Data showed that the mutant T. vi M8 reduced the growth of R. solani by 58 %. The mutants revealed significantly different (p<0.05) protein contents, chitinase and cellulase production (mg.mL-1) and activity (U.mL-1) compared to the wild-type strain. The highest extracellular protein production in the supernatant of chitinase and cellulase TFM was observed for the T.vi M11 and T.vi M17 strains, respectively. The T.vi M12 and wild-type strains secreted chitinase and cellulase significantly more than other strains did. Densitometry of SDS-PAGE gel bands indicated that both the amount and diversity of chitinase related proteins in the selected mutant (T. vi M8) were far higher than those of the wild-type. The diversity of molecular weight of proteins extracted from the T. virens M8 (20 proteins or bands) was very high compared to the wild-type (10 proteins) and mutant T.vi M15 (2 proteins). Conclusions: Overall, there was a strong link between the diversity of various chitinase proteins and the antagonistic properties of the mutant M8.