目的:植物-真菌共生可能在宿主的个体发育或物候发育过程中经历时间周转,这会影响寄主植物的生态要求。这项研究调查了Prasophyllum(兰科)中Ceratobodiaceae兰花菌根真菌(OMF)群落的时间周转,询问OMF群落是否由于兰花物候或个体发育而受到时间变化的影响。
方法:成虫的根,P.lindleyanum和P.sp.aff.来自澳大利亚的缬草在秋季和春季之间采样。将种子原位播种为“诱饵”,以探索发芽原球茎的菌根联系,将其与同时发生的成年植物的根中的OMF进行比较。培养依赖和独立测序方法用于扩增内部转录间隔区和线粒体大亚基基因座,在系统发育分析中分配给操作分类单元(OTU)的序列。发芽试验用于确定真菌OTU是否为菌根。
结果:OMF的持久性核心与Prasophyllum相关,CeratobasidiaceaeOMF在所有三个物种中占主导地位。物候周转发生在P.lindleyanum和P.sp.aff.Validum,但不是在P.Frenchii,对单个OTU显示特异性。在所有物种中都发生了个体发育周转。然而,物候和个体发育周转通常是由种群中不经常检测到的OTU的存在或不存在驱动的,否则这些OTU对一个或两个显性OTU表现出特异性。异位发芽试验显示,14个测试的OTU中有13个支持其寄主兰花的种子发芽,包括八个未在原球茎中发现的OTU。
结论:了解OMF周转对于保护受威胁的兰花及其菌根伴侣具有实际重要性。然而,对OMF周转进行分类的框架应侧重于对宿主工厂生命周期重要的OTU,我们认为这可能是那些经常被检测到或功能显著的。
OBJECTIVE: Plant-fungus symbioses may experience temporal turnover during the host\'s ontogenetic or phenological development, which can influence the host plant\'s ecological requirements. This study investigates temporal turnover of Ceratobasidiaceae
orchid mycorrhizal fungal (OMF) communities in Prasophyllum (Orchidaceae), asking if OMF communities are subject to temporal change due to
orchid phenology or ontogeny.
METHODS: Roots of adult Prasophyllum frenchii, P. lindleyanum and P. sp. aff. validum from Australia were sampled between autumn and spring. Seed was sown in situ as \'baits\' to explore the mycorrhizal associations of germinating protocorms, which were compared to OMF in roots of co-occurring adult plants. Culture dependent and independent sequencing methods were used to amplify the internal transcribed spacer and mitochondrial large subunit loci, with sequences assigned to Operational Taxonomic Units (OTUs) in phylogenetic analyses. Germination trials were used to determine if fungal OTUs were mycorrhizal.
RESULTS: A persistent core of OMF associated with Prasophyllum, with Ceratobasidiaceae OMF dominant in all three species. Phenological turnover occurred in P. lindleyanum and P. sp. aff. validum, but not in P. frenchii, which displayed specificity to a single OTU. Ontogenetic turnover occurred in all species. However, phenological and ontogenetic turnover was typically driven by the presence or absence of infrequently detected OTUs in populations that otherwise displayed specificity to one or two dominant OTUs. Ex situ germination trials showed 13 of 14 tested OTUs supported seed germination in their host
orchid, including eight OTUs that were not found in protocorms in situ.
CONCLUSIONS: An understanding of OMF turnover can have practical importance for the conservation of threatened orchids and their mycorrhizal partners. However, frameworks for classifying OMF turnover should focus on OTUs important to the life cycle of the host plant, which we suggest are likely to be those that are frequently detected or functionally significant.