Trichoderma endophyticum, T. asperellum, and T. harzianum suppress charcoal rot in soybean seeds infected by Macrophomina phaseolina

Abstract Soybean is one of the most important commodities in the world and is affected by several phytopathogens, such as the fungus Macrophomina phaseolina , which can occur at all stages of development, causing significant production losses. The use of different cultural, chemical and genetic control strategies has shown low efficiency against this phytopathogen. Thus, the objective of this study was to evaluate the use of Trichoderma asperellum , T. endophyticum, and T. harzianum in seed treatment to control M. phaseolina and promote plant growth. Healthy seeds inoculated with M. phaseolina were treated with the three Trichoderma species, the plant growth regulator Stimulate®, the insecticide Thiamethoxam, and combinations of Trichoderma species with Stimulate® or Thiamethoxam. The antagonistic capacity of Trichoderma species against M. phaseolina , their compatibility with Stimulate® and Thiamethoxam, seed germination, seedling vigor, plant growth, and their dry biomass were evaluated. Trichoderma species showed antagonism against M. phaseolina , especially T. endophyticum . In vitro , Stimulate® reduced the growth of T. endophyticum and T. harzianum , while Thiamethoxam reduced the growth of T. harzianum . M. phaseolina reduced soybean seed germination by approximately 80%. The three Trichoderma species increased the germination and vigor of infected seeds. In healthy seeds, T. harzianum reduced germination, while T. endophyticum combined with Stimulate® increased seedling vigor. These results show that T. endophyticum , T. harzianum, and T. asperellum are effective in treating seeds infected with M. phaseolina , and that the use of T. harzianum isolate CCT 7589 is not recommended for the treatment of healthy soybean seeds.