Diversity And Community Structure Of Root-associated Fungi Of Five Rhododendron Species

Plant in genus Rhododendron,being among the top ten traditional flowers of China,are repputated worldwide for its ornamental values in landscaping.In natural ecosystem,root of Ericaceae plants and soil fungi form mutualistic symbionts called ericoid mycorrhiza(ERM),which may have profound ecological significances for seedling establishment and community succession.Fully investigating diversity of root associated fungal community of Rhododendron plants in natural habitat will be helpful for a better understanding of ecological characteristic of mycorrhizal fungi,and for screening of fungal species or strains combinations which may pottentially effective in nursary stock cultivation and plant introduction.Information on diversity of root associated fungi community is also essential for the conservations of Rhododendron communtiy,as well as the root associated fungal community.To investigate fungal community structure associated with roots of Rhododendron plant species(i.e.,R.moulmainense?R.hainanense?R.simsii?R.cavaleriei?R.mariesii)habiting mountain areas of Diaoluo,Jianfeng and Bawangling of Hainan Island and Damingshan of Guangxi,ITS regions of fungi were amplified,cloned,sequenced and analyized.Preferences of fungi to Rhododendron plant speci es were tested by using Fisher's Exact Test.The effect of host identity and study sites on fungal community structuring were explored by using constraind ordination analysis.The results are as follows:(1)A total of 368 fungal OTUs(species)were detected in hair roots of 129 Rhododendron plant individuals.Of these fungi,233 species belong to Ascomycota,including Leotiomycetes(87),Sordariomycetes(58),Eurotiomycetes(34),Dothideomycetes(34),Pezizomycetes(2),Archaeorhizomycetes(1),Orbiliomycetes(1)and 16 unknown species;128 species belong to Basidiomycota,containing Agaricomycetes(123),Tremellomycetes(1),Atractiellomycetes(1),Cystobasidiomycetes(1)and 2 unknown species;In addition,4 and 2 species show close affinity to Zygomycota and Glomeromycota,1 species belong to Mucoromycotina,respectively.(Fungal groups of Helotiales(75 species)and Sebacinales(32)dominated in the root associated fungal community of Rhododendron forest in Hainan Island and Guangxi,China.(2)Estimated richness of fungi is 463(by Bootstrap estimator),which is much higher than the observed richness(368).Diversity of root associated fungi are every high,as indicated by Shannon-Weiner diversity index ranging from 3.94 to 4.65 for R.mariesii and R.moulmainense,respectively;and Simpson diversity index ranging from 0.986 to 0.966 for R.hainanense and R.cavaleriei,respectively.Shannon-Weiner's diversity index per varied from site to site ranging from 4.41 to 3.29 for Jianfeng mountains and Bawang mountains respectively.However,the observed Simpson's diversity index varied slightly among sites(0.984 to 0.961).(3)Some common fungal species showed strong host preference.Specifically,Sebacinaceae sp11 prefered to associate with R.cavaleriei(Fisher's Exact Test),Sordariomycetes sp15 prefered to associate with R.mariesii,Sebacinaceae sp8,Oidiodendron maius,Hyaloscyphaceae sp7 prefered to associate with R.hainanense,Sebacina sp6 refered to associate with R.moulmainense,and Mycena spl prefered to associated with R.simsii.Plant identity and study sites have significant effect on the compositional difference of fungal community,that each factor explained?10%variances in fungal species composition(Redundancy analysis).This finding suggested that other biotic and abiotic factors,which may potentially play key role in shaping root associated fungal community,are remain to be identified,yet.