Abstract:

Objective: This study aims to obtain a set of co-cultured wood rot fungi that can efficiently inhibit the growth of Bursaphelenchus xylophilus, so as to provide a theoretical basis for the research and development of a new environmentally friendly treatment way of wood stumps infected by B. xylophilus. Method: Seventeen co-cultured wood rot fungi were used as the object, and the inhibition rates during co-cultivation of white rot fungi (W) and brown rot fungi (B) were measured as preliminary screening criteria, and 15 groups of co-cultured fungi were obtained. The mortality of B. xylophilus in co-cultured fungal cultures was observed and calculated to identify B. xylophilus-inhibiting fungi. Pinus koraiensis and P. massoniana blocks were inoculated into jars with co-cultured fungi, and degradation rates were evaluated after specific periods. The selected optimal co-cultured fungi W5473 (Lenzites betulinus):B80995 (Fomitopsis pinicola) were analyzed via Fourier transform infrared (FTIR) spectroscopy to clarify the wood degradation status of P. koraiensis and P. massoniana. The co-cultured wood rot fungi were used as a microbial agent and applied in woodland trials, and the changes in B. xylophilus populations and stump degradation rates were counted and statistically analyzed to obtain the application effect of the microbial agent in the forest. Result: 1) Among 17 groups of co-cultured wood rot fungi, 2 groups exhibited sustained mutual inhibition throughout the cultivation process. The remaining 15 groups of co-cultured wood rot fungi without mutual inhibition were selected for further testing. 2) Among the 15 groups of co-cultured wood rot fungi obtained from the preliminary screening experiment, 9 groups achieved 100% inhibitory effect on B. xylophilus, and 14 groups caused the mortality rates of B. xylophilus more than 88%. At 30, 60, and 90 days of degradation of P. koraiensis and P. massoniana by co-cultured wood rot fungi, the degradation rate of W5473:B80995 was significantly higher than that of other co-cultured wood rot fungi. Based on the experimental results of the mortality of B. xylophilus and the degradation performance of wood blocks, the fungi W5473:B80995 were selected for the further experiment. 3) The fungi W5473:B80995 degraded P. massoniana more efficiently than P. koraiensis. Lignin degradation was slower than cellulose and hemicellulose. By day 90, hemicellulose degradation was complete, P. massoniana cellulose degradation slowed and stabilized, while P. koraiensis cellulose maintained higher degradation rates. Conclusion: The optimal co-cultured fungi W5473:B80995 have been screened from 17 candidates, and their suppression rate against B. xylophilus reaches 96.7%. At 90 days, the degradation rate of P. koraiensis reaches 37.58%, and of P. massoniana reaches 49.88%, showing strong application potential. The fungi W5473:B80995 have higher degradation efficiency for P. massoniana than for P. koraiensis. The decomposition of cellulose and hemicellulose degradation is concentrated in early-mid phases, while lignin remains recalcitrant. Degradation tends to stabilize in later phases for P. massoniana. After treatment with co-cultured wood rot fungi, B. xylophilus populations and stump mass are significantly reduced in the woodland applications. And B. xylophilus reduction is positively correlated to stump degradation rates.

Key words: co-cultured wood rot fungi, Bursaphelenchus xylophilus, treatment of stumps, degradation rate