Efficiency of different strains of Trichoderma on the control of Sclerotinia sclerotiorum, Sclerotium rolfsii and Sclerotium cepivorum

The aim of this work was to verify the efficiency of different isolates of Trichoderma spp. on the control of Sclerotinia sclerotiorum, Sclerotium rolfsii and Sclerotium cepivorum, and the influence they pose on the conidia production of Trichoderma spp. For mycelial growth, discs with inoculum of phytopathogens were placed on the center of the Petri dishes followed by the addition of two Trichoderma sp. discs on the opposite sides of the plate after 24 hours. Every 12 hours data were collected from colonies diameters and used for the analyses of Mycelial Growth Index (MGI) and Area Under the Curve of Mycelial Growth (AUCMG). The analyses were performed by a completely randomized design with two controls, a negative one without Trichoderma sp. and one with a commercial strain of Trichoderma harzianum. Spore solution for evaluation of conidia production were made by adding 10 mL of distilled water and scratching the surface of the colonies. For S. cepivorum, all Trichoderma spp. strains reduced both indexes tested.  However, while for MGI S. sclerotiorum also presented some reduction on the growth rate, the total area of this fungus was not affected. Sclerotium rolfsii strains of Trichoderma sp. from Lages and Curitibanos showed an effect on the reduction of AUCMG of this fungus, although none of the Trichoderma affected the growth rate of this phytopathogen. On the presence of S. sclerotiorum and S. cepivorum, none of the Trichoderma spp. showed any difference on conidia production when compared among themselves, nonetheless we did notice that on the presence of S. cepivorum, the strain from Rio do Sul retained its reproductive ability compared to control. Results obtained from this research can demonstrate the importance of biocontrol agents against different plant pathogens since it might have a specific antagonist-pathogen relation.