Abstract: In this study, fifty Clonostachys rosea strains derived from soils in different regions of Xizang were selected to screening efficient biocontrol strains. Their mycoparasitic abilities to Sclerotinia sclerotiorum sclerotia and control efficacies against Sclerotinia diseases on detached leaves of three kinds of vegetables were conducted, by which a highly-efficient C. rosea strain XRBL-1-1 was obtained. The parasitism level of XRBL-1-1 strain on sclerotia reached grade 4, and lesion areas on lettuce, Chinese cabbage, and oilseed lettuce leaves reduced to 50.7%, 64.1%, and 63.0%, respectively. In greenhouse, the control efficacy of 67.43% to Sclerotinia rot was achieved when the lettuce seedlings were sprayed with XRBL-1-1 fermentation broth at a concentration of 1×10⁷ spores/mL. When combined with a half-dose of the chemical fungicide Dimetachlone, the control efficacy was 82.31%, which was not significantly different compared with the chemical pesticide used alone. After application of the biocontrol fungus, the leaf area, chlorophyll content and biomass of lettuce increased by 65.9%, 175.0%, and 57.2%, respectively. Furthermore, C. rosea was able to induce plant resistance as well; the activities of catalase(CAT), peroxidase(POD), and superoxide dismutase(SOD) significantly increased, while malondialdehyde(MDA) content remarkably decreased in lettuce leaves(P<0.05). This research provides a theoretical basis for the green control of crop Sclerotinia diseases and lays a foundation for the development and application of highly-efficient C. rosea biocontrol products.

Key words: Clonostachys rosea, mycoparasitism, Sclerotinia sclerotiorum, Sclerotinia rot of vegetables, Growth-promoting effect