Antagonistic Potential of Different Species of Trichoderma Against Sclerotinia sclerotiorum

ABSTRACT

The fungus Trichoderma spp., commonly isolated from soil, rhizosphere, and as an endophyte in different plant tissues, displays greater antagonistic potential against different types of pathogens. This study aimed to select isolates of Trichoderma spp. from common bean and soybean fields in Minas Gerais State, Brazil, to evaluate their antagonism against Sclerotinia sclerotiorum. Forty‐eight isolates of Trichoderma spp. (30 rhizospheric, 11 epiphytic, four endophytic, and three from crop debris) were used in this study. Based on the sequencing of ITS, TEF1‐α, and RPB2 regions, these isolates were classified in eight species of Trichoderma as follows: T. harzianum (29 isolates), T. koningiopsis (five isolates), T. hamatum (four isolates), T. atroviride (four isolates), T. asperelloides (two isolates), T. longibrachiatum (two isolates), T. asperellum (one isolate), and T. neokoningii (one isolate). Eight isolates completely inhibited mycelial growth of S. sclerotiorum in the pairing culture test in vitro. Twenty‐four isolates displayed the greatest ability to parasitise sclerotia in soil with efficiency ranging from 79% to 99%. In water‐agar medium, 31 isolates inhibited myceliogenic germination of sclerotia from 78% to 100%, while seven isolates inhibited the carpogenic germination of sclerotia by more than 85%. Eight isolates affected the colonisation of detached leaflets of common bean and soybean plants by hyphae of S. sclerotiorum. The isolates UN34 and IM2 of T. harzianum were the most promising. The isolate UN34 reduced fungal survival and both myceliogenic and carpogenic germinations of sclerotia, while the colonisation of leaflets and stems of common bean and soybean plants by S. sclerotiorum was greatly lower by the IM2 isolate. In conclusion, the isolates of Trichoderma spp. obtained in this study displayed great potential for use for the biocontrol of S. sclerotiorum.