Influence of the biocontrol agents Trichoderma spp. on the structure and functionality of the edaphic microbial community in common bean cultivars (Phaseolus vulgaris L.) inoculated with Sclerotinia sclerotiorum (Lib.) de Bary

Abstract

Control of agricultural pathogens can be achieved by biological control agents, but information about their impacts on the native microbiota is scarce. In this work, the commercial biocontrol agent Trichoderma harzianum ESALQ-1306 and the experimental strain Trichoderma asperellum BRM-29104 were selected to determine the effects of their application on the edaphic microbial community and on their functional traits in common bean cultivation (Phaseolus vulgaris L.) infected with Sclerotinia sclerotiorum (Lib.) de Bary in the Brazilian savannah. Soil samples were collected before planting and after 90 days of cultivation. The bean yield and disease severity were estimated. Spores of arbuscular mycorrhizal fungi (AMF) were quantified and identified, and the rate of root colonisation was measured. The total colony-forming units (CFU), species richness and alpha diversity, production of hydrolytic enzymes, microbial carbon biomass, microbial soil respiration, metabolic diversity and glomalin mass were quantified. After 90 days of cultivation, the microbial richness, diversity and abundance increased significantly, stimulated by bean plant development. The biocontrol strains did not significantly change the abundance of CFU with enzymatic activity, as well as microbial soil respiration, the microbial carbon biomass, metabolic diversity, the glomalin mass and the root colonisation rates; however, they changed the composition of cultivable microbial communities. S. sclerotiorum was controlled, and bean productivity was maintained. Therefore, the cultivation time is the variable with the major influence over the structure and functionality of cultivable microbial communities and AMF. We identified microbial species not previously reported in this biome and determined that T. asperellum BRM-29104 has the potential to be used as a new eco-friendly commercial product against white mold.