Table_4_Characterizing the Ectomycorrhizal Fungal Community of Whitebark Pine in Interior British Columbia: Mature Trees, Natural Regeneration and Planted Seedlings.DOCX

Whitebark pine (Pinus albicaulis Engelm.; WBP) is an endangered subalpine tree species and requires associations with ectomycorrhizal fungi (ECMF) for survival and growth. Despite this obligate dependence, there are gaps in the identification of ECMF that associate with WBP. In addition, ECMF rarely feature in assessments of recovery actions and little is known about the relationship between ECMF and the insects and pathogens affecting WBP. We used next-generation sequencing to characterize ECMF occurring in soil and mycorrhizal root tip samples from naturally occurring mature WBP trees and seedlings as well as planted WBP seedlings in the Columbia Mountains of Interior British Columbia, Canada. ECMF data was paired with data on tree age, tree health and soil conditions. Thirty-three species and twenty-one genera of ECMF were identified with medium or high confidence from mycorrhizal root tip samples. Major groups were: generalist ascomycetes [Cenococcum, Meliniomyces (=Hyaloscypha)], Atheliales (Piloderma, Amphinema, Tylospora), non-ascomycetous generalists (e.g., Amphinema), associates of high-elevation conifers (species of Cortinarius, Russula) and Suilloids (Suillus, Rhizopogon). Differences in WBP ECMF with other, drier and southerly regions that have been studied previously, were consistent with a distinct forest type and an endemism hypothesis. Soil at the planting site and planted seedlings hosted a reduced ECMF community or were non-ectomycorrhizal, which can be explained by site factors and is expected to affect seedling survival. ECMF composition on mature trees was correlated with tree health, which may have implications for WBPs resistance to pathogens and signals that ECMF are affected by the decline of their host. Understanding the ecology of WBP ECMF and their relationship with tree performance is essential for WBP recovery efforts.

白皮松（Pinus albicaulis Engelm.；简称WBP）是一种濒危的亚高山乔木树种，其存活与生长均需与外生菌根真菌（ectomycorrhizal fungi，ECMF）形成共生关联。尽管存在这种绝对的共生依赖，但目前学界对与WBP共生的ECMF的鉴定仍存在诸多空白。此外，在WBP的恢复措施评估中，ECMF极少被纳入考量范畴，且学界对ECMF与危害WBP的昆虫及病原菌之间的关联也知之甚少。本研究采用下一代测序技术（next-generation sequencing），对加拿大不列颠哥伦比亚省内陆哥伦比亚山脉地区的天然成熟WBP植株、天然实生苗以及人工定植的WBP实生苗的土壤与菌根根尖样本中的ECMF进行了表征分析，并将ECMF检测数据与植株树龄、健康状况及土壤环境数据进行了关联分析。研究从菌根根尖样本中以中高置信度鉴定出21个属、33种ECMF，主要类群包括：广谱子囊菌类[空团菌属（Cenococcum）、梅里尼霉属（Meliniomyces，=透明盘菌属Hyaloscypha）]、阿太菌目（Atheliales，含皮尔蒙特霉属Piloderma、双担菌属Amphinema、卷头霉属Tylospora）、非子囊菌广谱类群（如双担菌属Amphinema）、高海拔针叶树共生类群（丝膜菌属Cortinarius、红菇属Russula物种）以及乳牛肝菌类群（Suilloids，含乳牛肝菌属Suillus、须腹菌属Rhizopogon）。此前研究的其他较干燥、更南部区域的WBP相关ECMF与本研究结果存在差异，这与独特森林类型的特征及特有性假说相符。定植点土壤及人工定植实生苗的ECMF群落丰度较低，甚至完全不形成外生菌根，该现象可由立地因子予以解释，且预计会对实生苗的存活产生不利影响。成熟植株的ECMF组成与植株健康状况显著相关，这可能对WBP的病原菌抗性具有重要意义，同时提示ECMF会受到宿主植株衰退的影响。明确WBP相关ECMF的生态学特征及其与植株生长状况的关联，对于WBP的恢复工作至关重要。