Abstract:[Background] Phytophthora capsici is a devastating soil-borne disease. Currently, it is mainly controlled by chemical fungicides, easily leading to environmental pollution and food contamination problems. [Objective] The aim is to isolate effective strains that can antagonize Phytophthora capsici. [Methods] Isolated strains were identified by the sequencing similarity of the internal transcribed spacer regions of rDNA and morphological characteristics. The antagonistic activity of the isolated strains was detected by the dual culture test. After treated with the extract from the isolated strains, malondialdehyde concentration, cellulase, β-glucosidase, and the polygalacturonase activity in Phytophthora capsaici were analyzed by the colorimetric method. [Results] All 11 isolated strains inhibited Phytophthora capsici growth. The isolated strains belonged to Trichoderma virens, Trichoderma harzianum, Trichoderma hamatum and Trichoderma asperellum species. Four strains (T. virens, T. harzianum, T. hamatum and T. virens) showed higher inhibition rates, which were 92.68%, 92.68%, 90.24% and 95.12%, respectively. After treated with the extract from the four isolated strains, the MDA concentration and the cellulase activity in P. capsici hyphae were significantly increased while the β-GC and PG activities were significantly decreased. The highest activity of chitinase was up to 0.831 U/mL with 0.783 U/mL more than that in control group. On the contrary, both of β-GC and PG activities were significantly decreased in the treated groups, in which the reduction rates ranged from 12.28% to 64.91% and 7.2% to 15.5%. [Conclusion] Four isolated Trichoderma spp. inhibited Phytophthora capsici growth by destroying its mycelial cytoderm structure, decreasing the activity of pathogenic factors and increasing the lipid peroxidation. This study provided a theoretical and technology support for resistant the Pepper Phytophthora blight.
