Primary Study On Mycorrhizal Fungus Diversity Of Rhododendron Pulchrum

Rhododendron,one of the important appreciative plant groups mainly originated in China, are highly valuable in gardening and florist gardening. Rhododondron mucronatum ,commonly known as Rhododendronspiciferum, grow tall and strong and they are adaptable and highly appreciative. They are widely used in the parks and street lawns of Shanghai. The prime time of their appreciativeness usually occurs one to three years after they are cultured. And they take on varying degrees of decline later on.Ericoid mycorrhizas,ERM,referred to members of family Ericaceae which have a distinctive form of the symbiosis,one of the special types of endotrophic mycorrhiza. ERM mycorrhiza plays important parts in absorbing the nutrition of Ericaceae plant,easing heavy metal pollution, fostering the growth of plants. In order to explore the declining cause of rhododendron and prepare for the basic data for regeneration technique, this study did research on the mycorrhizal infection rates and mycorrhizal fungi diversity of rhododendron culture in Shanghai and beyond and obtained a large amount of ERM fungus resources,which lays a good foundation for the further development and application of mycorrhizal fungi Therefore, the study about the separation, culture and diversity of mycorrhizal fungi is not only necessary, but also has practical implications. Through the study of the shapes and inheritance diversity of isolated mycorrhiza, the paper came to the following conclusions.1. Through the examination of the mycorrhizal infection rates of rhododendron mucronatum mycorrhiza from three districts, it is found that there is little difference between them, with most of them rated as grade-2 infect and with infection rate between 20%-25%, except that in landscape science institute and botanical garden of Shanghai, infection rates exceeds 26%, rated as grade-3 infect. That shows in natural environment, the infection degree of rhododendron mucronatum root is not high, and the mycorrhizal infection rates is to a certain extent influenced by the culturing conditions.2. The author uses Martin medium and MMN nutrient medium as the basis of the separation culture, separates 366 bacterial strain from three distributions and classifies it into 19 categories by combining form classification and ITS-RFLP molecular markers. The analysis of the data shows that rhododendron mucronatum isolated fungus of the three districts are rich in resources and that most of strain type show similarities in different sample lands,over 70% strain type shared by over two sample lands;Meantime, every sample land has its own special type, presenting obvious tendency of difference.3. The DNA of 50 selected bacterial strains were extracted,ITS sequences were obtained for representative isolates from each RFLP type and compared phylogenetically with sequences for known ericoid mycorrhizal endophytes and selected ascomycetes.Most of fungal isolates were also ascomycetes,the sequence similarity is 89%-99%. Among the 19 types of RFLP,9 types(nearly 50%)are closely related to Epacris microphylla root associated fungius;8 types are unclassified ascomycetes;2 types are unknown fungal strains.