Studies On Dark Septate Endophytes (DSE) In Yuanmou Region Of The Hot-dry Yalley

Jinsha River is located in the middle and upper reaches of Yangtze River. Hot-dry valley of Jinsha River, which is distributed mainly in Yunnan and Sichuan province, is formed under the comprehensive actions of geological, landscape, natural and human activities. This special ecosystem is charactered by its high annual temperature and heavy evaporation and its annual evaporation is higher than its annual precipitation. High population density and intensive exploitation in Hot-dry valley of Yunnan have been resulting in most serious soil and water loss, which have already threatened the ecosystems of drainage area of Yangtze River. So, the ecological improvement projects of the middle and upper reaches of Yangtze River have been listed as the key environmental improvement projects by Chinese government, in which the vegetation restoration of hot-dry valley is the most important core project. Dark septate endophytes are a assembly of fungi which widely distribute in soil and may have important ecological functions in natural ecosystems. Their existence has been found in terrestrial ecosystems and aquatic ecosystems. Moreover, they may play an important role in the restoration and biomediation of terrestrial ecosystems.Three habitats, representing cultivated lands (CL), old fields (OF) and never-cultivated fields (NCF), which located in hot-dry valley of Yuanmou, southwest China, were chosen as study sites. Based on the investigation of colonization in plants of three different ecosystems, 39 fungal isolates were obtained from surface sterilized root segments. Taxonomic affinity of the isolates was studied according to morphological observation and phylogenetic analysis of ITS1-5.8S-ITS2 region of rDNA. Inoculation experiments with maize were done with the isolates which are typical strains. Under different drought stress conditions, there are the effects of inoculation of strains on the tolerance of maize. The main results and conclusions of the thesis are:The DSE and AMF colonization of 64 plant species representing native plants, crops and introduced plants in CL, OF and NCF of hot-dry valley of Yuanmou was investigated by alkaline lysising and acid fuchsin staining. It was found that all plants surveyed in the three habitats were infected by DSE. The frequency of AMF in NCF, AL, OF are 86%, 78%, 96%. The results indicate that the plants are highly dependent on DSE and AMF in this hot and arid ecosystem.According to the morphological characters of the isolates on PDA and phylogenetic analysis of ITS regions, 8 isolates, including 77-2, 105-2,108-1 were identified to Cladosporium spp..After maize were inoculated with Cladosporium spp. and, DSE structures were observed in their roots, and no pathogenic symptom appeared in the maize. It has a positive effects to maize on different drought stress conditions. These results suggest that some species of Cladosporium are candidates of DSE.