Studies On The Anatomical Characteristic And Endophytic Fungi Diversity Of The Wild Plants With Extremely Small Populations Rhododendron Protistum Var, Giganteum

Big tree rhododendron, Rhododendron protistum var. giganteum (Forrest) D. F. Chamberlain, belongs to the family Ericaceae and subgenus Hymenanthes. This species is one of the tallest and most ancient rhododendron tree. It exhibits a very limited distribution, with only two populations found in the Gaoligong Mountains of Northwestern Yunnan Province in China. In addition, only approximately1,400individuals have been found. Considering its special habitat and extremely limited distribution, big tree rhododendron has been listed as a key species into the Conservation Program for Wild Plants with Extremely Small Population in China (2012-2015Operational Plan) in China. However, none researches on the anatomical characteristics and endophytic fungi diversity of this species was reported. Thus, in this research, we focused on the anatomy of roots, stems and leaf from the species by paraffin section as well as the microscopic characteristics of leaf epidermis between its related species. And also the endophytic fungi were directly isolated from the roots and identified both by colonial morphology and ITS sequencing, then their diversity and difference from the different population were analyzed. This paper is aimed to study the above basic biological characteristics of the species to provide scientific basis for its population protection, artificial breeding and population recovery. The major results and conclusions are given below:1The anatomy of roots, stems and leaf of Rhododendron protistum var. giganteum n were observed with paraffin section. The results showed that the secondary structures of its root are consist of periderm, phloem and xylem. And its stem’s primary structure consists of epidermis, cortex, phloem, cambium (obscure), xylem and pith. The anatomical structure of leaves showed that the leaf blades were typical dorsiventral leaf. It contains four parts:upper epidermis, lower epidermis, palisade tissue, spongy tissue. The upper epidermis is with thick cuticle and1-2layers of obviously wall thickened cell were under it. Also the stomata only distributed in lower epidermis, and densely covered with brown hairs on the lower epidermis, the ratio of palisade tissue to spongy tissue is about1. So it indicates that this species is a plant of toleranting hardy and drought. The characteristics of foliar trichome and seeds were observed under scanning electron microscopy.The resuts showed its foliar trichome consists of two different types. And the seeds are very tiny, obviously different between the back and the front side, the hilum side is flat and chalaza side is round, both sides with dense membranous wings.2The culturable endophytic fungi were isolated from two populations of great Rhododendron by the Martin medium, and identification of the fungi was according to morphology of the colony and hypha. The results showed that:287strains of endophytic fungi were isolated from400roots,153strains from DHT population can be classified into14kinds and only1strain and2strains were indentified at species (Cryptosporiopsis ericae) and genus level respectively by morpholoy, while the134stains from CZH population into11kinds and only the strain CZH-4was identified as Cryptosporiopsis ericae.3In this research, we analysised diversity of287stains of endophytic fungi by ITS sequencing. The results show that those stains were identified to17taxa,11were identified to species level and2to order level. Similar degree is very low, only three species, Cryptosporiopsis ericae, Ilyonectria radicicola and I. cyclaminicola, were both isolated from two population, C. ericae was the dominant species with dominance index35.95%from DHT and29.85%from CZH. Isolate rate, diversity index and richness index of DHT were higher than CZH, and the evenness index was contrary. These results indicated that diversity of endophytic fungi of big tree Rhododendron is different from different habitats, and had different characteristics of diversity.4Based on the above, the results show that:(1) the anatomical characteristics and special habitats of big tree Rhododendron show consistent adaptability, it suggests that we should strengthen the protection of the population, and give more attention to its the protection of the habitats;(2) The results of abundant endophytic fungi were isolated from the species show that its growth and fungi had close relationship. The method of vaccinateing superiority strains will provide a new thought for breakthroughing the bottleneck of growthing slowly, and easily death in the process of artificial cultivation.