Objective Isolation of stem rot antagonistic Trichoderma from Anoectochilus roxburghii, providing theoretical basis for the development of biocontrol fungi. in A. roxburghii.

Method Using wild cultivated A.roxburghiias as materials, Trichoderma strains were isolated using tissue isolation method. Morphological characteristics and homology analysis with ITS and rpb2 sequences were conducted for strains classification. Plate confrontation method were used for evaluating different Trichoderma strains resistance to stem rot ability, and the growth promoting effects of different Trichoderma strains were also processed.

Resulsts 3 Trichodermas trains as A21B-1, A21B-2 and A21E were isolated from the A. roxburghii via tissue isolation method. Combined with morphological characterization and ITS and rpb2 sequences homology identification, 3 Trichoderma strains were identified as T. rugulosum, T. koningiopsis and T. longifialidicum, respectively. Confrontation cultured showed that the 3 Trichoderma strains showed strong inhibitory effects on stem rot pathogen Fusarium oxysporum f. sp. opponiarum ASP01, and their inhibition rates reached 75.29%, 73.55% and 60.02%, respectively. The indoor control results showed that A21B-1 strain had a strong inhibitory effect on stem rot, after 15 d inoculation, the disease inhibition rate reached 91.9%, which could be used as a candidate strain for stem rot biological control fungi. The growth promotion experiments showed that Trichoderma strains significantly increased individual plant weight, height, stem diameter, leaf area, and SPAD value in A. roxburghii after 6 months grown. Among the 3 Trichoderma strains, plants innoculated with A21B-2 and A21E showed significant growth promotion effects with individual plant weight increased by 58.6% and 58.9%, leaf area increased by 66.8% and 59.7% compared to the controls, respectively. They could be used as candidate strains for growth promoting in A. roxburghii. At the same time, the application of Trichoderma strains effectively increased the content of polysaccharides and kinsenoside in A. roxburghii, A21B-2 strain showed the best effects, which content of polysaccharides and kinsenoside increased by 89.6% and 11.8% compared to the controls, could be used a candidate strain for promoting the accumulation of medicinal components in A. roxburghii.

Conclusion 3 different strains of Trichoderma have significant effects on inhibiting stem rot disease, promoting growth, and increasing polysaccharide content in A. roxburghii.