Comparative study of the antibacterial effects of wound secretions of different cultivars of Chinese fir

Background. The bark of Chinese fir (Cunninghamia lanceolata), the largest afforestation tree species in the forest areas of southern China, is susceptible to injuries and bites from small animals. The population of small animals has recently increased owing to improvements in the ecological environment across various forested areas, thus increasing the incidence of injuries in the bark of Chinese fir. Following such injuries, the bark secretes light yellow or milky white secretions, the function of which remains unclear. The present study aimed to reveal the antibacterial effect of exudates of different Chinese fir cultivars on five bacterial species. Methods. The research involved three-year-old plantations of Taxus chinensis var. koraiensis and Yangkou3 and three-year-old container plantations of Taxus chinensis var. pendula, Yang 061, and Yang 020. The antibacterial effects of exudates were analyzed using the filter paper diffusion method. The minimum inhibitory concentration for each secretion and the bacterial inhibition zone were determined. Results. The exudates of the different Chinese fir bark exhibited notable antibacterial effects on Bacillus subtilis, Salmonella paratyphi B, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. However, the extent of these antibacterial effects varied among the different Chinese fir cultivars, as the minimum inhibitory concentrations (MICs) of the exudates against the five bacterial species varied. The mean MIC of Pseudomonas aeruginosa was lower potency, whereas that of Escherichia coli was the lowest. Notably, the antibacterial efficacy of the exudates was mainly influenced by the composition of the secretions rather than the number of secretions, with organic acid compounds and terpenoids potentially contributing to the antibacterial effects against E. coli and Bacillus subtilis, respectively. Conclusion. This study demonstrates the antibacterial effect of wound secretion of different Chinese fir cultivars, highlighting their varying efficacy on different bacterial species. Moreover, the antibacterial ability of the exudates of the strains was mainly determined by the composition of the wound secretions, and there was no noticeable relationship with the number of wound secretions. The results of this study offers a theoretical basis for screen Chinese fir cultivars with high-disease-resistant.