Fungal Genetic Aspects Of Plateau Alpine Meadow Soil Affected By Seasonal Snow Cover In The Northwestern Sichuan

In order to prove up the effect of thickness variation of seasonal snow cover on diversity of soil fungi. In this study, subalpine meadow soil samples treated with different thickness of artificial snow cover and different quantity of additional litter in Songpan (3400metres high), the Western Sichuan plateau, were collected. By using both culture and uncultured fungi research method, the soil fungal community structure and genetic diversity has been systematically studied. The results are as the follows.(1) The genetic diversity of cultured fungi in tested soil was very abundent. From the9soil samples taken in January and May,30and23fungal strains were obtained by pour plate method. RAPD,18S rDNA PCR-RFLP and ITS sequence analysis of representative strains were determined to reveal the fungi diversity and phylogeny.The result of RAPD showed that30fungi strains in the January soil samples formed9groups at83%similarity level. By contrast,10groups were formed in the May soil samples, which illustrated that the genetic diversity of culturable fungi in the soil was highlighted.18S rDNA PCR-RFLP analysis indicated that there was very diverse among the cultured fungi, and7genetic groups in January soil samples and11genetic groups in May soil samples were formed at the level of85%similarity, respectively.Based on the results of18S rDNA PCR-RFLP analysis, eighteen representative fungal strains were selected to do the ITS sequence analysis, and the phylogenic tree was constructed. The results suggested that these fungal strains were mainly attributed to12genus, including Neurospora, Lecythophora, Fusarium, Aspergillus, Mucor, Monodicty, Verticillium, Sporothrix schenckii, Cladosporium, Penicillium, Mortierellas and Mycorrhizal fungi. In the soil samples collected in January, strains of genus Cladosporium and Morlierella were the predominant communities; however, in the soil samples collected in January, genus Cladosporium only existed in one soil sample (No.5-6), and the predominant species was genus Mortierella.(2)The community structure and fungi diversity analysis of uncultured fungi has also been done. PCR-DGGE amplification was determined the uncultured fungi in the subalpine meadow soil. In the amplification test, the total DNA was selected as a template, and PCR-DGGE was done. The results showed that the diversity of uncultured fungi was existed among the different treatments. The Patrick abundance index of tested soil was between12and23in January, but ranged from4to20in May. Furthermore,15representative bands were selected from the DGGE profile and coloned, the sequence was analyzed and phylogenetic tree was constructed. The results indicated that most of the fungi were unculturable, only band F7belonged to genus Candida, and was culturable fungi.(3) The mycorrhizal fungi diversity analysis for tested soil. According to Nested PCR-DGGE technique, the NS31/Glol of (arbuscular mycorrhizal) AM fungi is adopted DGGE analysis and the more clear and brightsome bands are recorded in the image of DGGE. The diversity index indicated that1-6(26) sample had the maximum Patrick abundance index and the1-1(15) had the minimum Patrick abundance index. According to PCR-DGGE image,19specific bands are selected to take colone and DNA sequence test. Phylogenetic analysis result shown that14bands are mcorrhizal fungi which attached to rhizoclosmatium and acaulospora, and other bands belong to ascomycetes and basidiomycete. The research reveales that arbuscular mycorrhizal (AM) fungus is mainly attributed to rhizoclosmatium and acaulospora under the seasonal snow cover in this area.(4) The present study indicates that the thickness of seasonal snow cover has notable positive correlation and organic material accession has no significant influency on the soil cultured fungi diversity. The result of PCR-DGGE for uncultured fungi showed that the thickness of seasonal snow cover was the major influence factor, and the influence of litter quantity added was not obvious for fungi diversity. However, mycorrhizal fungi abundance index was affected by both the thickness of seasonal snow cover and litter quantity added. As the thickness of seasonal snow cover and organic material rising, the abundance index had a tendency to grow.