PRELIMINARY RESEARCH ON ARBUSCULAR MYCORRHIZAL FUNGI OF DIPTEROCARPACEAE IN XISHUANGBANNA, SOUTHERN YUNNAN

In order to investigate the status of arbuscular mycorrhizae (AM) in tropical dipterocarpaceae forest, rhizospheric soil with roots of seventeen species of dipterocarpaceae plants grown in both native forests and plantations in tropical region Xishuangbanna, Yunnan Province, were sampled to determine their mycorrhizal colonization, spore density, isolation frequency, relative abundance and species richness of AM fungi. The mycorrhizal colonization rate of host plants were measured under a BX50 Olympus Microscope with Automatic Photo Micrographic System (320_640×) after staining with 0.5% acid fuchsin. Spores of AM fungi in aliquots (20 ml) of each soil were isolated by wet_sieving decanting and cane sugar centrifugal method, which were used to identify according to the newest taxonomic system described by Morton and Redecker (2001). Species richness was measured as the number of species compared with the number of individuals in the community. Results showed that most roots collected were colonized by AM fungi, typical arbuscules and vesicles were formed with various colonization rates (up to 40%, grade VIII), and 0_1.86 vesicles per mm root length. Species richness on Parashorea chinensis was the highest (4.31), while Shorea assamica showed the lowest (1.63). Hopea mollissima gave the maximum spore density (7.76), Vatica astrotricha the minimal (3.09). Thirty_two AM fungal species belonging to the genera Acaulospora, Glomus, Paraglomus, Achaeospora and Scutellospora were identified. The frequencies and relative abundances of AM fungi varied. Acaulospora and Glomus were likely the dominant proportion in the rhizospheric soil of dipterocarpus plants in the tropical region. It was suggested that most dipterocarpus plants can form typical AM and there was high species diversity of AM fungi in tropical dipterocarpaceae forest. The functional role of these AM fungi in the physiology of dipterocarpus plants needs further research.