Diversity And Composition Of Endophytic Fungi Of The Genus Paphiopedilum And Dendrobium In The Region

Orchidaceae is one of the largest families of vascular plants and is distributed in almost all terrestrial ecosystems.China has abundant orchid resources,about 1388 recorded species,mainly distributed in the tropical and subtropical regions of the south and southwest.However,due to habitat destruction,wild-handed predatory collections and climate change,most orchid plants are in danger of extinction.The seeds of orchids are as fine as dust and no endosperm,and their living stages are wholly or partially dependent on fungi to provide carbon and other essential resources.Previous studies on the interaction between orchids and fungi have focused on the classification and identification of endophytic fungi(including mycorrhizal fungi and non-mycorrhizal fungi),while the studies on endophytic fungi diversity and community composition of adult orchids in different environments are less.In this study,we studied the diversity and composition of endophytic fungi of the genus Paphiopedilum with more endemic species and the genus Dendrobium has many species in the Malhpo area,it provides a theoretical basis for understanding the formation and maintenance mechanisms of orchids diversity in the region.At the same time,the comparative study on the endophytic fungi diversity and composition of Dendrobium species under different artifmcial cultivation conditions provided theoretical support for the ex situ conservation of Dendrobium species.In this study,104 samples from 7 species of Paphiopedilum and 98 samples from 45 species of dendrobium were collected.Orchid fungi specific primers of ITS3 and ITS40F were used as targets,and amplicon sequencing was performed by using the second-generation sequencing technology.The main findings and conclusions are as follows:1.OTU914,OTU1489,OTU908,OTU437,OTU1071 and OTU1548 are common to six wild Paphiopedilum species,belonging to the unknown fungi 1,Malassezia globosa,Alternaria,unknown fungi 2,Malassezia restricta and Malasseziales;and the highest proportion of sequences contained is OTU1071(356532,6.98%).Except that no tulasnellaceae fungi were detected in Paphiopedilum malipoense and Paphiopedilum purpuratum cultivated in the local orchid Conservation Center,the dominant mycorrhizal fungi of all Paphiopedilum were Tulasnellaceae;In all Paphiopedilum species,the dominant non-mycorrhizal fungi are Malasseziaceae.The abundance and diversity of the endophytic fungi of the epiphytic Paphiopedilum villosum are high,and the Physodermataceae fungi are unique.2.The dominant endophytic fungi with Paphiopedilum hirsutissimum and Paphiopedilum dianthum are the same in the sympatric distribution,but some different endophytic fungi are also detected.The endophytic fungi group is quite differentat the family level between P.malipoense and Paphiopedilum micranthum distributed in the same region.At the same time,there are very few OTU numbers between the P.dianthum and the P.hirsutissimum,which are closely grown together in the wild(niche is the same).These results supporthypotheses that the total diversity of fungi present at a location can be divided into subsets of multiple coexisting orchids,and there may be few overlapping between the subsets.Secondly,the abundance of tulasnellaceae in the root base of P.micranthum was significantly higher than that in the limestone gap.Combined with the fact that tulasnellaceae fungi were not detected in P.malipoense distributed in the same region as P.micranthum in the limestone gap,it strongly proved that different Paphiopedilum species have strong selectivity and preference for mycorrhizal fungi.3.Compared with the endophytic fungal community of wild Paphiopedilum henryanum,the abundance of Malasseziaceae and Wallemiaceae was significantly increased in the transplanted P.henryanum,while the Tulasnellaceae,Dothioraceae and Trichosporonaceae were significantly decreased.Interestingly,the down-regulated three types of fungi were not detected in the transplanted P.purpuratum,but the up-regulated two types of fungi were dominant fungi.To some extent,this may suggest that orchids will establish different dominant fungi in different habitats to adapt to the new habitat,and only the original habitat is beneficial to the establishment of Tulasnellaceae symbionts.4.The results of ITS sequencing show that 3251 OTUs were isolated from 98 samples of Dendrobium.Among all the samples,the more frequently occurring fungi were Malasseziaceae,Meruliaceae and Psathyrellaceae fungi.Depending on the sampling location,in addition to the same high frequency of fungi,the frequency of some endophytic fungi varies greatly depending on the sampling location.5.By comparing the endophytic fungi of the same species of Dendrobium grown in different environments,it can be found that the composition of endophytic fungi in Dendrobium species with relatively wide distribution is relatively simple,while the composition of endophytic fungi in Dendrobium species with narrow distribution is more complex.This may be a process of co-evolution of Dendrobium and endophytic fungi,and the distribution of endophytic fungi may limit the distribution of Dendrobium.The conclusions obtained in this paper not only provide a theoretical basis for the recovery of wild Paphiopedilum and Dendrobium populations by mycorrhizal technology,but also have certain guiding significance for further exploring the relationship between community structure and environment of endophytic fungi in Orchidaceae and the ecological function of each fungus.