Diversidade de Trichoderma spp. no bioma Caatinga e o potencial antagonistico no controle de Rhizoctonia solani

Abstract

Biological control is an important tool for managing plant diseases and has been increasingly adopted in agricultural systems. Biological control agents can occur naturally or be introduced to suppress pathogens. Among these agents, species of the genus Trichoderma have been widely used as the basis for fungicidal biological products. This study aimed to assess the diversity of Trichoderma in the Caatinga biome compared with agricultural areas, and to evaluate their effectiveness against Rhizoctonia solani. Soil samples were collected from natural Caatinga and banana (Musa spp.) plantations in Jaíba, Minas Gerais, Brazil. The mean population density of Trichoderma, estimated on semi-selective medium, was 2.5 log CFU/g of soil in the Caatinga and 1.4 log CFU/g in banana plantations, representing 8.5% and 3.4% of total fungal populations, respectively. A total of 80 isolates 54 from Caatinga and 26 from banana plantations were analyzed by BOX-PCR for genetic diversity, resulting in 67 genetic groups based on amplified band patterns. Fifteen isolates were randomly selected based on genetic grouping and identified through sequencing of the tef1 region: 4 were identified as T. longibrachiatum, 1 as T. neokoningii, 6 as T. pseudoasperelloides, and 4 as T. hunanense. In planta antagonism, assays against R. solani showed that isolate PEL39 (T. neokoningii) reduced disease incidence by 26%, and isolate RBS12 (T. pseudoasperelloides) reduced incidence by 12%, compared to the untreated control, while T. longibrachiatum and T. hunanense isolates showed no significant effect. These results highlight variability in the biocontrol activity among isolates, and future studies will focus on evaluating the antagonistic potential of untested isolates in planta.