Department of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB, T6G 2G2, Canada.
Department of Forest and Conservation Sciences, University of British Columbia, 3219-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
Appl Microbiol Biotechnol. 2023 May;107(10):3341-3352. doi: 10.1007/s00253-023-12499-z. Epub 2023 Apr 5.
The mountain pine beetle (MPB) has infested over 16 million hectares of pine forests in western Canada, killing over 50% of mature lodgepole pine, Pinus contorta, in British Columbia alone. There are few tools available to manage irruptive bark beetle populations and to mitigate tree mortality. Beauveria bassiana is an entomopathogenic fungus that causes mortality to several bark beetle species. However, the potential for B. bassiana as a biocontrol agent against pine beetle populations is unknown. We selected three strains of B. bassiana from several culture collections and evaluated their conidial stability under cold storage, in planta (greenhouse, and pine bolts) and in natura (forest stand, pine bolts, and live pines) conditions. The stability assays showed that all fungal strains maintained a minimum effective conidial yield through the assay durations (3-12 weeks). In addition, we adapted a biphasic liquid-solid fermentation approach for the large-scale production of conidial biomass, yielding up to a 100-fold increase in production. In greenhouse virulence assays, the mean lethal time of MPBs was reduced to 3-4 days upon treatment with B. bassiana, where high B. bassiana-associated mycosis was also observed. Furthermore, the application of B. bassiana formulation substantially affected the gallery network of MPBs in bolts in the field, resulting in shorter larval galleries and significantly reduced offspring production. Indeed, high titer treatments reduced the mean larvae per gallery to virtually zero. Together these results demonstrate that B. bassiana may be a viable biocontrol tool to reduce mountain pine beetle populations in pine forests in western Canada. KEY POINTS: • Three B. bassiana strains identified to be stable at various test conditions. • Large-scale conidial biomass production using liquid-solid biphasic fermentation. • Reproductive success of D. ponderosae significantly reduced by B. bassiana formulation.
山松甲虫（MPB）已经侵袭了加拿大西部超过 1600 万公顷的松林，仅在不列颠哥伦比亚省就导致超过 50%的成熟黑云杉（Pinus contorta）死亡。目前几乎没有工具可以用来管理突发性树皮甲虫种群和减轻树木死亡率。球孢白僵菌是一种昆虫病原真菌，可导致几种树皮甲虫物种死亡。然而，球孢白僵菌作为一种针对松甲虫种群的生物防治剂的潜力尚不清楚。我们从几个培养物中选择了三种球孢白僵菌菌株，并评估了它们在冷藏、植物体内（温室和松钉）和自然条件下（森林林分、松钉和活松树）的分生孢子稳定性。稳定性测定表明，所有真菌菌株在测定持续时间内（3-12 周）都保持了最低有效分生孢子产量。此外，我们还采用了两相液体-固体发酵方法来大规模生产分生孢子生物量，产量最高可增加 100 倍。在温室毒力测定中，松墨天牛的平均致死时间在接种球孢白僵菌后缩短至 3-4 天，同时也观察到高球孢白僵菌相关真菌病。此外，球孢白僵菌制剂的应用显著影响了现场松钉中的 MPB 坑道网络，导致幼虫坑道变短，后代产量显著降低。事实上，高滴度处理将每个坑道中的幼虫平均数量降低到几乎为零。这些结果表明，球孢白僵菌可能是一种可行的生物防治工具，可以减少加拿大西部松林中山地松甲虫的数量。要点：• 三种球孢白僵菌菌株在各种测试条件下被鉴定为稳定。• 使用液体-固体两相发酵大规模生产分生孢子生物量。• 球孢白僵菌制剂显著降低了白松墨天牛的繁殖成功率。
