Isolation, identification and biocontrol effect of Trichoderma antagonistic to Sclerotinia disease of Asarum heterotropoides Fr. Schmidt var. mandshuricum (Maxim) Kitag.

Abstract:

[Background] Sclerotinia disease is one of the main root diseases of Asarum heterotropoides Fr. Schmidt var. mandshuricum (Maxim) Kitag. Trichoderma is extensively used for biocontrol owing to the fungistatic activity. Recently, the control of Sclerotinia asari by Trichoderma has attracted the interest of scholars. [Objective] Trichoderma strains were isolated from the rhizosphere soil of healthy A. heterotropoides Fr. Schmidt var. mandshuricum (Maxim) Kitag. with the dilution-plate method and those antagonistic to S. asari were screened out. [Methods] The inhibition of the isolated strains (plate confrontation method), the volatile and non-volatile strain metabolites, and strain fermentation broth (growth rate method) on S. asari was respectively determined. The malondialdehyde (MDA) content (thiobarbituric acid method), catalase (CAT) activity (ultraviolet absorption method), superoxide dismutase (SOD) activity (nitroblue tetrazolium assay), and peroxidase (POD) activity (guaiacol method) of S. asari treated with the selected Trichoderma were determined. [Results] A total of 14 Trichoderma strains were isolated and identified based on morphological observation and ITS-RPB2 sequence alignment as T. harzianum, T. hamatum, T. koningiopsis, T. atroviride, T. brevicompactum, and T. tomentosum, respectively. The inhibition rates of T. hamatum A26, T. koningiopsis B30, T. hamatum C6, and T. harzianum A17 on S. asari were all above 90%. The volatile metabolites of T. hamatum C6 demonstrated the highest inhibition rate (53.73%±0.07%), and the non-volatile metabolites showed stronger inhibitory effect, particularly those of A17 (inhibition rate: >75%), A26 (inhibition rate: >75%), C6 (inhibition rate: >75%), and B30 (inhibition rate: 100%). Thus, strains A17, A26, B30, and C6 had the strongest control effect and the inhibition rates of the fermentation broth of these 4 Trichoderma strains against S. asari were 56.33%±0.12%, 77.22%±0.06%, 82.28%±0.03%, and 46.20%±0.04%, respectively. After being treated with the non-volatile metabolites of the 4 strains for 7 days, S. asari saw significantly increased MDA content, particularly the S. asari strains treated with the non-volatile metabolites of A26 (MDA content was 7.7 times that of the control). Besides, the antioxidant enzyme activity of S. asari decreased. To be specific, the activity of CAT, SOD, and POD declined by 19.67%-75.84%, 4.71%-68.71%, and 3.57%-67.86%, respectively, as compared with that of the control. [Conclusion] Trichoderma A17, A26, B30, and C6 isolated from the rhizosphere soil of healthy plants of A. heterotropoides Fr. Schmidt var. mandshuricum (Maxim) Kitag. can be used for the biocontrol of S. asari.