Avaliação do potencial de isolados de Trichoderma spp. no biocontrole de doenças da soja e no tratamento de sementes

Abstract

A variety of polyvalent strains of Trichoderma isolates are available on the market for biological control of plant pests and diseases, in addition to being in the native and anthropized field representing global diversity. The success of biological control using efficient antagonists has allowed the creation and registration of a large number of products for disease control in agriculture. Soybeans have become one of the most important crops for agribusiness, playing an important role in the national economy. In this context, the use of high quality seeds constitutes an extremely important tool for the farmer. Aiming to evaluate the potential of Trichoderma spp. in the biocontrol of soybean diseases and in the treatment of seeds. The study was conducted in two stages: i) Antagonistic potential: from a population of 25 isolates of Trichoderma ssp. and three phytopathogens represented by Athelia rolfsii, Macrophomina phaseolina, Paramyrothecium roridum, were submitted in the "in vitro" assay using the technique of confrontation of isolates in Petri dishes. Trichoderma and three pathogen isolates (A. rolfsii, M. phaseolina and P. Roridum) totaling 75 treatments in three replications, totaling 75 treatments. After seven days, the colony diameter (mm) and the Bell scale (1982) were measured. Athelia rolfsii and Macrophomina phaseolina allowed to identify the best groups of Trichoderma spp. isolates. Incubation was at 27 °C in a 12-hour photoperiod. After seven days, the colony diameter (mm) and the Bell scale (1982) were measured. A. rolfsii and M. phaseolina allowed to identify the best groups of Trichoderma spp. All isolates of Trichoderma spp. inhibited the growth of P. roridum. The SLVD1 isolate was in all groups with the highest percentage of growth inhibition of the evaluated phytopathogens, showing potential as a biocontrol agent. ii) Seed germination: to evaluate the effect of Trichoderma ssp. in the germination of soybean seeds, being tested the 25 isolates of Trichoderma ssp., in the treatment of soybean seeds, the weight of a thousand seeds and mechanical damage were evaluated. For the evaluation of the physiological quality of the seeds submitted to the treatments, the variables were evaluated in the laboratory: first germination count, normal plants, abnormal plants, dead seeds. In addition, the length of the primary root and quantification of the secondary root were evaluated. The experimental design was completely randomized, consisting of 26 treatments (25 treatments + control). Each treatment consisted of four experimental units consisting of a gerbox box with 25 seeds. The application of Trichoderma spp. favors agronomic variables, influencing the size of seedlings, increase of primary and lateral roots and precocity in germination. The isolates SLD1, SLV23, T-SYN9 obtained the best results, being promising candidates for field tests, aiming at the treatment of soybean seeds.