| Alpine grassland accounts for one-third of total grassland area of China and plays an important role in food security and ecological civilization construction. However, the alpine grassland have been degraded seriously due to overgrazing and climate change, plant disease become an limited factor to alpine grassland productivity. In this research, the soil from light grazing (LG), moderate grazing (MG) and high grazing (HG) were collected separately and then the soil from each grazing intensities were treated as follows:(1) Sterized (without microorganism, NM); (2) Without treatment (AM+Root invading fungi);(2) Sterilized and return the root invading fungi(Root invading fungi); (4) Sterilized and inoculated Glomus intraradices and G versiforme. The dominant plant seeds, Elymus nutans and E. sibiricus from Ma Qu Alpine grassland of Lanzhou University were collected and planted in pots contained above soils at greenhouse, aimed to study the interactions of the two plants and AM fungi and root invading fungi. The main results as follows:(1) Total of 11 AM fungi belong to 3 genera and 13 genera of root invading fungi were isolated and identified from Ma Qu Alpine grassland. The diversity of the two type fungi were decreased with the increasing of the grazing intensity, of which, The diversity of the AM fungi under LG, MG and HG were 11 species belong to 3 genera,10 species belong to 3 genera, and 8 species belong to 2 genera, respectively. Root invading fungi diversity under the three grazing intensity were 12 genera for LG and MG,8 genera for HG.No AM fungi were found infect the plant grown in NM soil and root invading soil. Plant formed AM structure grown in the soil without treatment and inoculated AM fungi and the colonization was increased with the increasing the grazing intensity. E. sibiricus given higher AM colonization than E. nutans in all grazing intensity and soil treatment.(2) Powdery mildew cuased by Blumeria graminis were happened on the E. nutans and E. sibiricus during the plants grown in the greenhouse. The incidence of powdery mildew varied with plants, grazing intensity and soil treatment, of which the mean disease incidence of E. nutans was 87% higher than that of E. sibiricus (51%). Grazing and soil treat have not shown affect on plants resistance to powdery mildew besides AM fungi increased E. nutans resitance to powdery mildew infection significantly.(3) The two plants given highest biomass both in the HG in all soil treatment, and there was no significantly different between LG and MG. The biomass of E. nutans in HG were 14.19% and 13.76% higher than that in LG and MG The biomass of E. sibiricus were 19.66% and 13.76% higher than that in LG and MG. Plants grown in sterized soil given the highest biomass while the soil without any treatment (AM fungi and root invading fungi) had the lowest biomass.(4) AM fungi and root invading fungi increased the photosynthetic rate of E. sibiricus significantly. Plant grown in sterized soil given the lowest photosynthetic rate, which was 44.50%, 40.98% and 50.61% lower than that in AM fungi+ root invading fungi soil, root invading fungi soil and the inoculated soil.(5) Grazing intensity can affect disease resistance related enzyme activity. MG and HG given the higher SOD enzyme activity than that in LG which was 27.32% and 27.10% higher than that in in LG. However, POD enzyme and PPO enzyme were higher in LG, POD enzyme activity were 30.67% and 40.55% higher than that in MG and HG. PPO enzyme activity were 8.31% and 11.09% higher than that in MG and HG. The contents of CAT enzyme activity and MDA were similar among the grazing intensity. |
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