| Orchidaceae is one of the most abundant families in the world,with rich species diversity and economic value,and is also one of the most endangered plant groups.Orchidaceae is a typical mycorrhizal plant,almost all orchid plants are symbiotic with fungi,and mycorrhizal symbiosis almost runs through the whole life cycle of orchid plants from seed germination to flowering and fruiting.It is considered to be one of the main factors affecting diversity and spatial distribution of Orchidaceae.Exploring effect of mycorrhizal fungi on the growth,development and distribution of orchids is of great significance for further study of relationship between orchids and fungi,protection of orchid resources,ecological restoration of wild populations and industrial management.In this paper,according to different spatial distribution patterns,widely distributed Orchidaceae(Spiranthes sinensis),Orchidaceae plants with vertical gradient,the same species of Orchidaceae(Bulbophyllum andersonii)at different elevations and the epiphytic Orchidaceae plants coexisting on different host trees in the same habitat were systematically studied by IlluminaMiseq high-throughput sequencing technique;this is to gain a more comprehensive understanding of the correlation between the composition and differentiation of mycorrhizal fungal community and the spatial distribution pattern of Orchidaceae.The main results are as follows:1.In order to explore the mycorrhizal fungal community composition of widely distributed Spiranthes sinensis,according to the spatial order from south to north,samples of 6 populations were collected from 6 plots in China(Beijing,Shanghai,Jiangxi,Guangxi,Yunnan and Gansu),and 5 groups were randomly collected from each population.The results showed that the mycorrhizal fungal community of Spiranthes sinensis produced a total sequence number of 862840,belonging to 1501 OTUs.The total sequence of ascomycetes is 465800,belonging to 752 OTUs.The total sequence of basidiomycetes is 250759,belonging to 267 OTUs.Among them,Ceratobasidiaceae,Tulasnellaceae,Sebacinales,Thelephoraceae,Inocybaceae,Russulaceae and Psathyrellaceae are common mycorrhizal fungi.Basidiomycaceae fungi are the dominant group,with a total of 179233 sequences,accounting for 71.48%of the total basidiomycete sequences.In addition,there were significant differences in mycorrhizal fungal communities of Orchidaceae among different regions(R2=0.37,pseudo-F=2.81,p<0.01).In addition,th ere were significant differences in mycorrhizal fungal communities of Orchidaceae among different regions..At the same time,some of the mycorrhizal fungi were shared(7 OTUs were detected in all samples),and most of the other fungi were differentiated,indicating that wide-distributed orchids can coexist with different kinds of fungi in different regions and different environments.2.In the study of mycorrhizal fungal community composition of orchids with vertical gradient,30 genera and 103 species of orchids were collected from Mount Victoria in Myanmar Natma Taung National Park(NTNP),with an altitude span of 480-3080m.The results showed that the total number of generated sequences was 2992770,belonging to 8774 OTUs.The total sequence of basidiomycetes is 2686323,belonging to 4720 OTUs,accounting for 90%of the total sequence,and the rest are a small number of ascomycetes and unidentified species.Among them,common mycorrhizal fungi have been found.The dominant group was Ceratobasidiaceae,Serendipitaceae and Sebacinaceae,each accounting for about 25%of the sequence of basidiomycetes.With the increase of altitude,the mean pairwise distance(MPD)among OMF decreased linearly(R2=0.233,pseudo-F=30.66,p<0.01),indicating that the OMF groups symbiotic with orchids became more concentrated with the increase of altitude.In the mycorrhizal fungal community of the same Orchidaceae at different altitudes,the total sequence number was 249228,belonging to 654 OTUs,basidiomycetes with a total sequence of 136834,belonging to 164 OTUs,and the rest were ascomycetes and unidentified species.The dominant groups are also Ceratobasidiaceae and Serendipitaceae,accounting for about 50%of the total basidiomycetes.There were significant differences in mycorrhizal fungal communities of the same orchid plants at different elevations(R2=0.260,p-value<0.01),indicating that the environmental differences caused by altitude have an effect on the mycorrhizal fungal communities of the same orchid plants.3,In the study of coexisting epiphytic orchid mycorrhizal fungal community,24 different orchid species were collected from three host trees(Pistacia weinmannifolia)15-20m apart in Xishuangbanna National Forest Park.The total sequence number was 1906704,belonging to 3912 OTUs.The total sequence of basidiomycetes is 1588152,belonging to 1964 OTUs.The rests are ascomycetes and unidentified species.Among the common orchid mycorrhizal fungi,except the dominant Serendipitaceae(45%),Ceratobasidiaceae,Tulasnellaceae,Sebacinales,Thelephoraceae,Inocybaceae have been found.In addition,the mycorrhizal fungal community showed obvious differentiation on three different host trees(treel,2,3)(R2=0.395,p<0.01).The results of further pairwise comparative analysis showed significant differences(tree 1/tree 2:R2=0.225,p-value=0.001;tree 1/tree 3:R2=0.376,p-value=0.001;tree 2/tree 3:R2=0.294,p-value=0.001),and the mycorrhizal fungal communities of the same plant are also significantly different in different host trees.The proportion of shared OTUs is less than 10%,indicating that the niche in the same habitat also affects orchid mycorrhizal fungal community's composition.This paper's study shows the composition differences of orchid mycorrhizal fungal communities in different spatial distribution patterns and some factors causing the differences were clarified.The results of this study provide a theoretical basis for further conservation of medicinal orchid plants and ecological restoration of wild populations. |
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