Objective Elaeocarpus spp. stem blight is a newly discovered branch disease on Elaeocarpus spp. caused by Pseudocryphonectria elaeocarpicola in recent years. At present, there is limited research on this disease and there is still a lack of effective prevention and control measures. This study aims to isolate and screen for effective biocontrol strains from wastewater samples at the distillery's discharge outlet that antagonize P. elaeocarpicola by using dilution separation method, and to clarify taxonomic status, and biological characteristics of the antagonistic strain, and to provide reference for further utilization of this strain as a biocontrol agent.

Method The inhibitory effect of antagonistic strains on P. elaeocarpicola was studied using plate two-point confrontation method. Based on morphology and ITS-rpb2-tef1 sequence analysis, the taxonomic status of the strains was determined. The growth rate method was used to determine the optimal growth medium, carbon source, nitrogen source, inorganic salt, temperature, pH value of biological characteristics of the strain.

Result Two antagonistic fungal strains P45-1 and P45-2 were selected by confrontation in vitro from 8 strains isolated from wastewater samples. After the secondary screening, the strain P45-1 showed the better antifungal efficacy, with the inhibition rates of 67.25% against P. elaeocarpicola. The volatile metabolites of the strain P45-1 have no inhibitory effect on P. elaeocarpicola, the inhibition rate of the fermentation broth of the strain P45-1 against P. elaeocarpicola was 52.58%. The strain P45-1 was identified as Trichoderma virens based on morphological characteristics and rpb2-tef1 sequence analysis. There existed significant differences among media for this fungal growth, the optimal growth medium was MEA. The optimal carbon was mannitol. The optimal nitrogen source was L-asparagine. The optimal inorganic salt were KNO₃ and no inorganic salt. The optimal temperature was 25℃, and the hypha was inhibited significantly when the temperature fell below 20℃ or rose above 35℃. This fungus also tolerated very wide range of pH, and grew well under pH 4.0 to 7.0. The optimal pH was 5.0.

Conclusion T. virens P45-1 isolated from wastewater samples at the distillery's discharge outlet can be used for the biocontrol of P. elaeocarpicola. The experimental results of biological characteristics of the strain P45-1 clarified the optimal conditions for mycelial growth.