Trichoderma species for biocontrol of soil-borne plant pathogens of pasture species

Soil-borne plant pathogens such as Rhizoctonia solani (Kuhn), Pythium ultimum (Trow) and Sclerotinia trifoliorum (Eriks) can reduce grass and forage legume establishment. The potential for biocontrol of these pathogens by Trichoderma fungi was evaluated. Following dual culture assays, nine Trichoderma isolates (five of Trichoderma atroviride and one each of Trichoderma hamatum, Trichoderma koningiopsis, Trichoderma viride and Trichoderma virens) were chosen for assessment in pot experiments. In the presence of R. solani, perennial ryegrass (Lolium perenne L.) emergence was increased by 60-150% by two isolates of T. atroviride and by 35-212% by the isolate of T. virens, with the increase depending on growing medium and amount of pathogen inoculum. Red clover (Trifolium pratense L.) emergence in the presence of S. trifoliorum was significantly increased by two T. atroviride isolates and the T. hamatum isolate. In the presence of P. ultimum, white clover (Trifolium repens L.) emergence was increased by 25-42% by one isolate of T. atroviride and the T. hamatum isolate. However, for all three pasture species, some Trichoderma isolates reduced seedling emergence. Seedling growth (shoot and root fresh weight/plant) of the three pasture species was significantly increased by one or more T. atroviride isolates. On the basis of these results for both disease reduction and growth promotion, four T. atroviride isolates were selected for field assessment as biocontrol agents of soil-borne pathogens of pasture species.