| The microorganisms that cause asymptomatic infections in living plant tissues have been called endophytes.They formed complicated symbiotic relationship during the long process of co-evolution.According to the archaeological discovery,endophytes have existed in the plant before 400 million years ago,which makes people to think that endophytes may have played an important role in the process of plants transition from aquatic environment to terrestrial environment as well as in the process of evolution from lower plant species to higher species.However,there is little researches on it until now.Dawei Mountain,which located in Yunnan Province,Southwest China,is the only and the most comprehensive region which has humid rainforests and the tropical mountain forests perpendicular band series in mainland China and it has never been attacked by "the quaternary glacier" in the geological history,so it can provide research materials with the historical continuity.For this reason,14 plant species[Bryophyte(Mnium sp.,Marchantia polymorpha,Polytrichum commune,Hylocomium splendens),Pteridophyte(Plagiogyria maxima,Alsophila costularis,Diacalpe aspidioides,Coniogramme petelotii,Asplenium normale),Spermatophyte(Taiwania cryptomerioides,Cunninghamia lanceolata,Embelia polypodioides,Vernonia saligna,Rhododendron irroratum)]were collected from Dawei Mountain and their endophytic fungi were isolated,and fungal endophytic diversity between plants in different evolutional degree were compared.The results are as follows:(1)A total of 3526 culturable endophytic fungi were isolated from 2640 segments of 14 plant species,and the colonization rate,isolation rate and the Shannon Indices ranged from 93.75%to 100%,1.01 to 1.95 and 1.74 to 3.22,respectively.The results indicated that the endophytic fungi diversity in this region is very high.(2)There is no significant difference in fungal endophytic isolation rate between photosynthesis tissues and rhizoid tissues of bryophytes,however,it showed significant difference among roots,stems and leaves of pteridophytes.It suggested that the richness of endophytic fungi changed with the improvement of the plant and tissue differentiation.(3)Based on morphological characteristics and 18S rDNA sequence analyses,all of the isolates were identified to 68 taxa,of which Xylaria sp.and Collectotrichurn sp.were the dominant genera.In addition,they displayed some specificity or preferences in the individual and tissue level.(4)The Shannon Indices of 14 plant species ranged from 0.409 to 0.756,indicating that fungal endophytes community of plants in Dawei Mountain are similar in a certain extent.Moreover,we found that the Shannon Indices of plants having closer evolutional degree is higher than that of plants having further evolutional degree,and the isolation rate of some fungal endophytic taxa(Penicillium sp.,Trichoderma sp.,etc.)were lowered and others(Phomopsis sp.,Nigrospora oryzae,etc.)were increased with plants' evolution.(5)We found that the intraspecific genetic diversity of the dominant endophytic fungi-Xylaria was very rich through 18S r DNA analysis.Moreover,it was found that the group A only was isolated from spermatophytes,which suggested that some endophytic fungi only associated with the host plants in a certain evolutional degree.However,to verify this,more work need to do in the future. |
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