| Arbuscular mycorrhizal Fungi belongs to Glomale of Zygomycete, Zygomycota. It is a kind of obligate parasitic fungi, which can form mutual symbiosis with most of nature plant root. Researches on Arbuscular mycorrhizal fungi have always been key point. AMF infection can promote growth of various plants. Many studies have proved that vesicles and dendritic cells of Arbuscular mycorrhizal fungi hyphae formed in the root cells can improve rhizosphere microenvironment, nutrient absorption and water metabolism of host plants, protect the plant roots and promote the growth of overground and underground part. In addition, mycorrhiza is helpful to enhancing plant resistance, increasing economic yield.Azotobacters widely exist in soil ecosystem. Typical symbiotic nitrogen fixations forming between rhizobia and leguminous plants like clover effectively improve the nitrogen level of leguminous plants. Meanwhile, clover is a kind of mycorrhizal plants, which can be infected by a variety of arbuscular mycorrhizal fungi. So, leguminous plants infected with both Rhizobia and AMF will achieve double symbiosis. They can interact each other on root nodule and mycorrhiza formation, nitrogen fixation improvement, mutual specific recognition and so on. This dual symbiosis and microecological structure play an important role in agricultural production. By means of the hyphal link connection, dual symbiosis effect is conducted to the host plant root, solving the key problems, for instance, low organic matter and fertility of soil, low utilization rate of fertilizer and high production cost in orchard ecosystem.Pear is one of the most important cultivating fruits in China. In order to adjust the varietal structure of pear industry, the cultivation of the south early-maturing pears is vigorously promoted. South early-maturing pears in southern district are cultivated mainly in the mountainous area, facing some environmental stress like shallow soil, deficience of nutrients and high temperature and drought. Using leguminous plant as materials of sod cultivation and taking double symbiosis as the breakthrough point. This paper study the effects of AMF inoculation on the Rhizobia activity and nitrogen fixation effects, and growth of pear seedlings, soil nutrient and soil microbial community structure variation under double symbiosis mode. Then the test also indicated most conducive kind of the arbuscular mycorrhizal, which is effective to high quality pear production. There was few related reports in this research field.Using the crested pear seedlings grafted on P.Pashia as experiment materials, we intercropped clover symbiosing with Rhizobia and different AMF under the pot condition to study the interaction effect among clover, Rhizobia and AMF, the change of soil microorganism environment and physiological metabolism of pear. seven treatments were respectively carried out: clover intercropping; single inoculated with Glomus etunicatum(GE), Glomus intraradices(GI), and Glomus mosseae(GM); clover intercropping and inoculated with Glomus etunicatum(GE), Glomus intraradices(GI), and Glomus mosseae(GM); blank control treatment. There were 5 pots each treatment plot, repeated three times, 120 pots in all were disposed by random teams. The main results were as follows:(1). Clover can be infected by GM, GI and GE three kinds of arbuscular mycorrhizal fungi, and the infection rates were all more than 69%, of which infection rate of GM was 71.5%. At the same time clover can be infected by rhizobium and achieved dual symbiosis relationship.(2). The nodules amount and survival rate of clover and rhizosphere nitrogenize activity were significantly increased inoculated with AMF. Nodules amount and nitrogen fixation activity were associated variation of mycorrhizal infection rate, which showed that AMF inoculation significantly promoted the growth of rhizobium and improved the nitrogenase activity to 1.45 μmol(C2H4)·g-1·h-1. The research results also indicated that mycorrhiza infection rate of clover roots inoculated with both rhizobium and AMF was higher than that inoculated with AMF, inoculation of rhizobium also significantly improved the AMF infection activity.(3). Sod-culture with white clover infected by AMF, in this culture system, the hyphae bridge formed in rhizosphere accelerated the absorption and transport of mineral nutrition and moisture of the pear roots, which promoting the pear seedlings growth and development. Under sod-culture, pear inoculated with three AMF significantly increased the maximum lateral root length, new root amounts, root volume and root/shoot ratio. Plant height, stem diameter and leaf area of pear seedlings were significantly improved at the same time. Compared comprehensively, sod-culture combined inoculated with GM showed up the best effect, respectively increased 43.32%, 58.38%, 48.66% than the contral treatment.(4). Inoculation of AMF significantly promoted the growth and development of P.Pashia root mainly in expanding the absorbent scope of the root system, increasing the fibrous root amounts, enhancing the root activity and increasing the content of root soluble sugar and protein. The results discovered that mycorrhiza remarkably accolated the absorption of leaf mineral elements N, P, K, S, Zn, Fe, Ca and Mg. improved the soil enzyme activity and nutrient utilization. Under the condition of sod-culture, P.Pashia inoculated with AMF further effectively increased the content of organic matter, organic carbon, total N, P, K, and available N, P, K in soil.(5). On the basis of improving nutrition metabolism, inoculated with AMF notably increased the chlorophyll a and chlorophyll b content of pear leaf, especially under the condition of sod-culture. In the same treatment, net photosynthetic rate, stomatal conductance, and transpiration rate, intercellular CO2 concentration of pear leaf were observably higher than that of no inoculation.(6). Intercropping mode in pear orchard can improve the rhizosphere microflora. The number of bacteria, actinomyces and nitrogen-fixing bacteria were increased after inoculation of AMF, the number of fungi was the highest in the control treatment. The effect sod-culture for soil improvement was significantly better when inoculated with GM or GI compared with other treatments. Thereinto, sod-culture and inoculated with GM was 39.26% higher than the contral treatment.(7). In most of the treatments, soil organic matter, total N, P, K, available N, P, K showed significant or extremely significant correlation to soil microorganism, and the correlation coefficient between azotobacter and available N was 0.952. The content of soil organic matter, total N, P, K, available N, P, K presented different degrees of positive correlation with soil enzyme activity of urease, and the correlation coefficient between urease and available P was 0.979. Between the amounts of bacteria, actinomyces and azotobacter and soil enzyme activity of urease, protease, phosphatase, invertase were characterized by highly significant positive correlation, and the correlation coefficient between urease and azotobacter was 0.934. While, fungi amount was significantly negatively related to soil enzyme activity. |
PDF Full Text Request