Objective  This study aimed to screen and identify the antagonistic fungi with strong inhibitory effects against Diplodia sapinea, the pathogen of Pinus massoniana shoot blight, to provide a theoretical basis for the biocontrol of P. massoniana shoot blight.

Method Strains of D. sapinea isolated and purified from the phloem of diseased trunks and shoots of P. massoniana in Chongqing and the four fungal antagonistic strains were used as materials. The plate confrontation culture and mycelial growth rate methods were employed to screen for antagonistic fungi against D. sapinea. The antagonistic fungi were identified based on morphology and phylogenetic analysis, and the biocontrol mechanism was preliminarily explored by microscopic observation of hyphal interactions between D. sapinea and the antagonistic fungi.

Result The results of preliminary screening showed that all four fungal antagonistic strains inhibited the growth of D. sapinea, among which strains CXY4103 (Lasiodiplodia sp.) and CGMCC 41126 (Trichoderma sp.) were the most effective. The results of re-screening revealed that the strain CGMCC 41126 had the best inhibitory effect on D. sapinea, with its fermentation filtrate achieving an inhibition rate of 45.17% against the pathogen. Through morphological observation and phylogenetic analysis of the tef1 and rpb2 gene sequences, the strain CGMCC 41126 was identified as Trichoderma paraviridescens. According to the microscopic observation, T. paraviridescens could contact and coil around the mycelia of D. spinea. The antifungal spectrum result indicated that T. paraviridescens had antagonistic effect on Ophiostoma bicolor, O. pseudobicolor, Endoconidiophora fujiensis, E. polonica, Gnomoniopsis daii and G. chinensis.

Conclusion A strain of antagonistic fungus with strong inhibitory effect against D. sapinea, the pathogen of P. massoniana shoot blight, was screened and identified as T. paraviridescens. Its antifungal spectrum is extensive. This study provides a potential antagonistic fungal resource and a theoretical basis for the biocontrol of P. massoniana shoot blight.