Evaluation of Trichoderma isolates as biocontrol measure against Claviceps purpurea

Abstract

AbstractClaviceps purpurea causes ergot, a floral disease of major cereal crops, such as winter rye and winter triticale. The dark sclerotia formed by C. purpurea contain numerous toxic ergot alkaloids, which pose a major health risk for humans and animals when ingested. The countermeasures against ergot infection are currently limited to intensive tillage, seed cleaning, crop rotation or integration of optical sorting machines to remove ergot from cereals before processing. However, these practices confer only a minor protective effect and are highly energy-demanding. Thus, more effective and sustainable plant protection measures to combat ergot infections in cereals are needed. The application of Trichoderma spp. as biological control agent has already proven successful against a wide range of phytopathogenic fungi. However, there is only minor scientific evidence about its protective capacity against C. purpurea in cereal crops. In our study, we therefore investigated the antagonistic potential of several Trichoderma isolates against C. purpurea and their ability to confer protection against ergot infection. In initial in vitro tests and confrontation assays, we quantified and compared the production of iron-chelating compounds and hydrolytic enzymes as well as the antagonistic activity against C. purpurea sclerotia and mycelial cultures. Several strains showed high antifungal capacity and growth inhibitory effects towards C. purpurea. Selected Trichoderma strains were then tested for their potential to protect rye (Secale cereale) plants from ergot infection within a greenhouse trial. Rhizosphere-inoculated plants displayed a decreased disease severity compared to plants that had been sprayed with Trichoderma spores above-ground. Gene expression analysis by reverse transcription quantitative PCR also indicated the induction of systemic defense reactions. Overall, our data suggest that individual Trichoderma isolates possess a high antagonistic potential towards C. purpurea, which could be effective by direct mycoparasitism and by inducing systemic plant resistance, and therefore provide important guidance towards the development of Trichoderma treatments of cereals as biocontrol measure against ergot. Graphical abstract