ABSTRACT

Fungal symbionts occur in all plant tissues, and many aid their host plants with critical functions, including nutrient acquisition, defense against pathogens, and tolerance of abiotic stress. “Core” taxa in the plant mycobiome, defined as fungi present across individuals, populations, or time, may be particularly crucial to plant survival during the challenging seedling stage. However, studies on core seed fungi are limited to individual sampling sites, raising the question of whether core taxa exist across large geographic scales. We addressed this question using both culture-based and culture-free techniques to identify the fungi found in individual seeds collected from nine provenances across the range of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii), a foundation tree species in the Pacific Northwest and a globally important timber crop that is propagated commercially by seed. Two key findings emerged: (i) Seed mycobiome composition differed among seed provenances. (ii) Despite variation in the seed mycobiome, we detected four core members, none of which is a known pathogen of Douglas-fir: Trichoderma spp., Hormonema macrosporum, Mucor plumbeus, and Talaromyces rugulosus. Our results support the concept of a core seed microbiome, yet additional work is needed to determine the functional consequences of core taxa for seedling germination, growth, survival, and competition.

摘要

真菌共生体存在于所有植物组织中，许多真菌共生体帮助宿主植物发挥关键功能，包括获取养分、防御病原体和耐受非生物胁迫。植物真菌群中的“核心”分类群，定义为存在于个体、种群或时间中的真菌，在具有挑战性的幼苗阶段可能对植物生存特别重要。然而，对核心种子真菌的研究仅限于单个采样点，提出了核心分类群是否存在于大地理范围内的问题。我们使用基于培养和非培养技术来识别从沿海花旗松 ( Pseudotsuga menziesii var. menziesii)，太平洋西北部的基础树种和全球重要的木材作物，通过种子进行商业繁殖。出现了两个关键发现：（i）种子来源之间的种子微生物组组成不同。(ii) 尽管种子菌群存在差异，但我们检测到四个核心成员，其中没有一个是道格拉斯冷杉的已知病原体：木霉属、大孢子菌、毛毛霉和Talaromyces rugulosus。我们的结果支持核心种子微生物组的概念，但还需要更多的工作来确定核心分类群对幼苗萌发、生长、生存和竞争的功能影响。