Antagonism of Trichoderma-based biofungicides against Brazilian and North American isolates of Sclerotinia sclerotiorum and growth promotion of soybean

The antagonistic activity of Trichoderma asperellum (aerial conidia) and T. harzianum (microsclerotia) Pers. (1801) (Hypocreales: Hypocreaceae) was evaluated against six isolates of Sclerotinia sclerotiorum (Lib.) de Bary (Helotiales: Sclerotiniaceae) from Brazil and the USA and further assessed for their enhancement of soybean growth. The fungicide thiophanate-methyl was included as a standard in all experiments. In vitro assay revealed that thiophanate-methyl and Trichoderma spp. effectively suppressed carpogenic and myceliogenic germination of sclerotia. The S. sclerotiorum isolates from Brazil appeared to be less susceptible than those from the USA to both chemical and biological treatments. The in vivo seed coating test using thiophanate-methyl or Trichoderma spp. substantially improved seed germination and suppressed growth of all S. sclerotiorum isolates to varying degrees. Moreover, soybean biomass of shoots and roots, and root nodulation were increased by either thiophanate-methyl or Trichoderma species. Collectively, these results underline the antagonistic activity of Trichoderma spp. against S. sclerotiorum isolates, the importance of Trichoderma spp. to improve soybean growth, and the bioactivity of Trichoderma microsclerotia through seed coating.