Isolation, identification, and fermentation condition optimization of two marine Trichoderma strains antagonizing Phytophthora parasitica

Abstract:

[Background] A mangrove forest is a special plant community distributed in the intertidal zone of tropical and sub-tropical regions, where a large number of microorganisms exist in the sediments, serving as potential sources for screening agents for the control of plant diseases. [Objective] To screen fungal strains antagonizing Phytophthora parasitica from the microorganisms isolated from mangrove sediments. [Methods] Fungal strains were isolated from the sediments of Xiamen Wuyuan Bay mangrove wetland and then identified based on the similarity of ITS sequences. The dual culture method was employed to select the Trichoderma strains with high activities of inhibiting P.parasitica. The effects of different fermentation conditions on the sporulation of selected strains were examined. [Results] The fungi isolated from the sediments of Xiamen Wuyuan Bay mangrove wetland belonged to 15 genera of 2 phyla. The inhibitory activities of Trichoderma harzianum M312 and Trichoderma virens M552 against P.parasitica were higher than those of other Trichoderma strains. The two strains (M312 and M552) should be cultured at 25 ℃ and 31 ℃, respectively, pH 7.0, and low salinity for high sporulation. [Conclusion] T. harzianum M312 and T.virens M552 screened from the sediments of Xiamen Wuyuan Bay mangrove wetland could be used as candidate fungi for the biocontrol against tobacco black shank, while the fermentation conditions need to be optimized before commercial application.

Key words:Phytophthora parasitica;mangrove sediment;fungal diversity;Trichoderma;fermentation conditions