Growth Characteristics And Diversity Of Arbuscular Mycorrhizal Fungi Associated With A Desert Plant Artemisia Ordosica

Arbuscular mycorrhizal (AM) fungi is the largest and most important member of the soil microflora, which have the capacity form a symbiotic association with approximately 80% of terrestrial plant species. AM fungi have many beneficial physiologies and the ecology effects to the plant growth. It also plays an important role in the evolution and distribution of host plant, such as maintain of biological diversity. In semi-arid inland desert habitats where are water shortages, evapotranspiration severe, nutrient poor, desert plant symbiosis with AM fungi is one of the important measures. By now, the culture of AM fungi had been widely studied, but pure fungal cultures remain a big challenge. They could not be industrial producted by fermention like Ectomycorrhizas. Research and development of AM fungal biotechnology antimicrobial remains to be further studied. The in vitro culture is the key. The spore germation is the primary factor in vitro culture of AM fungi. The hyphal growth is the prerequisite for the formation of AM fungi infection. So in vitro spore germation and hyphal growth of AM fungi are affected by a variety of factors including: species charcteristics, age of spore and self-inhibition, internal factors and external factors, such as pH, culture temperature, water-agar, incubation period and culture cycle.We sampled, in April 2007, the following 4 representative sites in the Mu Us Sandland and Tengger Desert regions: Yulin Psammophyte Garden (Yulin), Yanchi Desert Shrub Garden (Yanchi), Ordos Sandland Ecological Research Station (Research Station) and Shapotou Desert Research and Experiment Station (Shapotou). We collected soil samples from the rhizosphere of Artemisia ordosica. We elucidated the diversity of AM fungi and did the in vitro culture to optimize the factors on spore germination and hyphal growth. The results of thesis researchs provide the scientific basis and germ plasm resource for the applications of AM biotechnology in vegetation restoration and ecology reconstruction of desert. Main research results were as follows:(1) Twtenty eight AM fungi of 4 genera were separated in the experiment. Of these, 16 species belonged to Glomus, 7 to Acaulospora, 4 to Scutellospore and 1 to Diversispora. Glomus and Acaulospora were dominant genera at the four sampling sites. Scutellospore was common genera in Yulin, Yanchi and Research Station. There was only 1 species of Diversispora in Research Station(2) G. reticulatum and A.bireticulata were common species and G. mosseae was the dominant species at the four sampling sites. G. deserticola was common genera in the Mu Us Sandland. G. fasciculatumm was common genera in Yulin and Yanchi. A. excauata was common genera in Yanchi and Research Station. G. multicaule was common genera in Shapotou.(3) Several factors that influence germination of arbuscular mycorrhizal (AMF) spores and hyphal growth were optimized by L₁₆(4⁵) multifactor orthogonal experiment and the best level of spore germination were determined. The results showed that the best technical conditions are as following: 8of pH, 10 g/L of water agar, 10 days of culture cycle, 20 days of aging storage, 28℃of culture temperature.(4) In all other treatments, no obvious differences were detected among spore germination rates, all reaching about 40 % when were not added root exudates. Hyphal growth significantly varied with different treatments. Number of hyphal branches and length of germ hyphae were both higher on the lupin and ryegrass treatments than on WA medium.(5) Maximum germ tube growth occurred when 10 mgL^-1 root exudates was used, whereas 100 mgL^-1 root exudates depressed germ tube growth. The result obviously shows that root exudates can improve the hyphal growth, compared with WA.