海南濒危树种保育圃白木香与降香黄檀幼苗根部真菌谱系与生态型多样性比较

Comparison of phylogenetic diversity and ecological types of root-associated fungi on Aquilaria sinensis and Dalbergia odorifera seedlings in an endangered plant restoration nursery of Hainan Island

摘要:

【背景】根部真菌是影响植物幼苗存活、定植和生长的重要因子之一，但是苗圃培育的幼苗根部真菌物种组成与生态学特性尚不清楚。【目的】研究苗圃培育的白木香(Aquilaria sinensis)与降香黄檀(Dalbergia odorifera)幼苗根部真菌群落谱系与生态型多样性，以及宿主植物对根部真菌群落结构的影响。【方法】采集幼苗根尖样品提取基因组DNA，用真菌通用引物与丛枝菌根真菌(AMF)特异性引物扩增真菌rDNA-ITS区，经克隆、测序、序列分析鉴定真菌。通过基于核酸与Metadata数据关联分析的FUNGuild软件，划分根部真菌的营养型和共位群。采用非公制多维尺度分析法(NMDS)研究幼苗根部真菌群落物种组成差异与宿主植物物种及形态指标的关系。【结果】白木香与降香黄檀幼苗根部真菌物种丰富，达51个OTU；谱系多样性较高，涉及毛霉菌门(Mucoromycota，51%)、子囊菌门(Ascomycota，43%)以及担子菌门(Basidiomycota，6%)。这些根部真菌涉及不同的营养型与共位群，包括共生型真菌29种，频度较高的如Glomeromycetes sp. 2、Rhizophagus irregularis等，二者均属于AMF共位群；腐生营养型真菌5种，如Talaromyces pinophilus、Rhizopycnis vagum等；病原型真菌2种，是Mycoleptodiscus sp.和Fusarium phaseoli；还有15种其生态类型不确定。NMDS分析结果表明，宿主植物物种、株高、地径、叶面积对根部真菌群落物种组成的影响不显著。然而，株高对AMF群落的物种组成有较弱的影响。【结论】本苗圃条件下，土壤中本土性根部真菌繁殖体较为充足，白木香与降香黄檀幼苗根部真菌群落谱系多样性较高，多种营养型与共位群的根部真菌共存；此外，采用真菌通用引物对ITS1F/ITS4研究根部真菌群落物种多样性时，AMF多样性可能会被极度低估。

Abstract:

[Background] Root-associated fungi (RAF) are essential for seedling survival, establishment and growth. However, little is known about the identity and ecological characteristics of RAFnaturally established on seedling roots. [Objective] To reveal phylogenetic diversities and ecological types of RAF naturally established on nursery grown seedling of Aquilaria sinensis and Dalbergia odorifera and to evaluate the host effects on RAF community structuring. [Methods] root samples were collected to extract DNA, from which fungal ITS region was amplified, cloned and sequenced by using both universal and specific fungal primer pairs. Phylogenetic placements of fungi were inferred by ITS sequence analysis. The putative trophic modes and guilds of RAF were assigned by functional analysis with the FUNGuild software. Effects of plant species, height, basal diameter and leaf area on root-associated fungal species composition were determined by non-metric multidimensional scaling (NMDS) analysis. [Results] A. sinensis and D. odorifera seedlings grown in nurseries were naturally colonized by a highly diverse suite of RAF, including Mucoromycota (51%), Ascomycota (43%) and Basidiomycota (6%). These RAF can be assigned to multiple trophic modes and guilds including symbiotroph (29 species) representing by Glomeromycetes sp. 2, Rhizophagus irregularis, and saprotroph (5 species) representing by Talaromyces pinophilus and Rhizopycnis vagum. In addition, two fungal species, Mycoleptodiscus sp. and Fusarium phaseoli were assigned to pathotroph, while ecological characteristics of 15 species are unclear. NMDS analysis indicated that the effects of host plant species, plant height, basal diameter and leaf area of seedling on root-associated fungi were not significant. However weak effect of plant height was found in Arbuscular mycorrhiza fungi fungal community. [Conclusion] The RAF inoculum is high in culture media of this nursery that seedlings were associated with phylogenetically distant and multiple trophic modes and guilds of fungi. Diversity of AMF might be underrepresented when universal primers such as ITS1F/ITS4 were applied to investigate the diversity of RAF community.