Two Novel Trichoderma Species and their Antagonistic Activity against Sclerotia-producing Plant Pathogens

Trichoderma species are among the most employed fungal biocontrol agents in global agriculture. One mechanism of activity of these fungi is mycoparasitism, which is responsible for degrading the cell wall of other fungi through the production of enzymes such as chitinases and cellulases. This mechanism is capable of targeting resistant structures like sclerotia and chlamydospores produced by pathogens such as Sclerotinia sclerotiorum and Stromatinia cepivora. Several Trichoderma species have been reported as antagonists of these pathogens, but most described species were not explored for their antagonism against sclerotia-producing pathogens. The objective of this study was to characterize new species of the Trichoderma genus and evaluate their antagonistic potential against pathogens that produce sclerotia. The taxonomical novelties reported in this study are the description of two novel species, T. variabile and T. littericola from the Restinga ecosystem and T. nordicum is reported from Brazil, showing that this species has a broader distribution than previously thought. In addition to that, T. nigricans was shown to be an invalid species that should be considered a synonym of T. nordicum according to the rule of priority in taxonomical descriptions. These strains showed antagonistic potential against S. sclerotiorum and S. cepivora in vitro, especially T. nordicum and T. littericola, which were superior to T. harzianum from a commercial product. This study contributed to extend our knowledge on the diversity of Trichoderma species from the Restinga ecosystem and points out to their potential use in the biological control of plant pathogens that produce sclerotia.