Impact of Seed Treatments with Fungal Biocontrol Agents on Enzymatic Activities and Phenolic Content of Soybean under Greenhouse and Field Conditions

Fungi in the genus Trichoderma are widely used as biological control agents because they can suppress plant pathogens and activate plant defense systems. In the present study, efficacy of microbial antagonists viz., T. harzianum and T. viride or their combination was evaluated against the pathogenic fungus Macrophomina phaseolina and their effect on enzymatic activities and phenol content of soybean [Glycine max (L.) Merr.] plants. Soybean seeds were inoculated with T. harzianum and T. viride separately or in combination, and sown in pots under green house and under field conditions. Host enzymatic activities and phenol levels were measured at 14, 28 and 42 days after sowing (DAS) in both field and greenhouse experiments. Seed treatments with T. harzianum, T. viride or their combination increased peroxidase, polyphenol oxidase and β-1, 3-glucanase activities, and also the total phenol content in soybean leaves as compared to a non-treated control treatment. Concentration of peroxidase and β-1, 3-glucanasepeaked at 14 DAS and decreased thereafter in all the treatments under greenhouse and field conditions. All the treatments showed the highest levels of total phenols and polyphenol-oxidase at 28 DAS under both greenhouse and field conditions. At 14 DAS in both trials, the combination of T. viride + T. harzianum resulted in the highest level of peroxidase and β-1, 3-glucanase activities. This combination also resulted in the highest levels of total phenols and polyphenol oxidase content at 28 DAS. Our findings demonstrated that application of Trichoderma species as seed treatment has potential to trigger key mechanisms of systemically acquired resistance in soybean, and thereby enhanced efficacy of disease management tactics. © 2021 Friends Science Publishers