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

Authors: MACENA, ANDREIA - Universidade Estadual De Maringá; KOBORI, NILCE - Universidade Estadual De Maringá; MASCARIN, GABRIEL - Embrapa; VIDA, JOAO - Universidade Estadual De Maringá; Hartman, Glen

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2019
Publication Date: 10/19/2019
Citation: Macena, A., Kobori, N.N., Mascarin, G.M., Vida, J.B., Hartman, G.L. 2019. Antagonism of Trichoderma-based biofungicides against Brazilian and North American isolates of Sclerotinia sclerotiorum and growth promotion of soybean. Biocontrol. 65:235-246. https://doi.org/10.1007/s10526-019-09976-8.
DOI: https://doi.org/10.1007/s10526-019-09976-8

Interpretive Summary: Trichoderma species are ubiquitous, cosmopolitan soil- and root-inhabiting fungi that display multifunctional roles such as plant growth promoters and biocontrol agents. Trichoderma species are widely known to be effective against numerous soil-borne fungal pathogens including the destructive disease known as Sclerotinia stem rot or white mold of soybean. The bio efficacy of two Trichoderma species was evaluated against isolates of S. sclerotiorum from Brazil and the USA and assessed for their enhancement of soybean growth. The two Trichoderma species suppressed sexual (carpogenic) and asexual (myceliogenic germination) reproduction of sclerotia compared to the control. Soybean seeds coated with Trichoderma species and challenged with seven isolates of the Sclerotinia stem rot fungus after sowing seeds substantially improved seed germination over the control regardless of the isolate. For plants not inoculated with Sclerotinia stem rot fungus, biomass of shoots and roots, and root nodulation increased when seeds were treated with Trichoderma species compared to the controls. These results underscore the potential of using Trichoderma species to protect soybean plants against the Sclerotinia stem rot fungus and highlights the growth promoting attributes of Trichoderma species for increasing soybean biomass. This information is important to soybean growers, soybean managers, and others in the industry that are interest in non-pesticide use to control plant diseases.

Technical Abstract: Trichoderma spp. are ubiquitous cosmopolitan soil and root inhabitants displaying multifunctional roles such as plant growth promoters and biocontrol agents. Trichoderma spp. are widely known to be effective against numerous soil-borne fungal pathogens including the destructive disease known as sclerotinia stem rot or white mold of soybean caused by Sclerotinia sclerotiorum. The bioefficacy of T. asperellum (aerial conidia) and T. harzianum (microsclerotia) was evaluated against isolates of S. sclerotiorum 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 the first experiment, sclerotia of S. sclerotiorum were topically treated with thiophanate-methyl, T. asperellum, or T. harzianum under laboratory conditions. The thiophanate-methyl and the Trichoderma-based treatments effectively suppressed carpogenic and myceliogenic germination of sclerotia compared to the control. The S. sclerotiorum isolates from Brazil was less susceptible than the isolate from the USA to either thiophanate-methyl or the Trichoderma-based treatments. In the second experiment, soybean seeds were coated with thiophanate-methyl or Trichoderma-based treatments and challenged with seven isolates of S. sclerotiorum after sowing seeds in potting soil. Thiophanate-methyl and Trichoderma-based treatments substantially improved seed germination regardless of pathogen isolates. In the absence of protection, there was no soybean seed germination. For plants not inoculated with S. sclerotiorum, biomass of shoots and roots, and root nodulation increased when seeds were treated with thiophanate-methyl or Trichoderma-based treatments compared to the controls. Collectively, these results underscore the potential of using Trichoderma products against distinct geographic S. sclerotiorum isolates and highlights for the first time the bioactivity of microsclerotia of T. harzianum through seed coating against this plant pathogen.