| Arbuscular mycorrhizal (AM) fungi exist ubiquitously in most soil types. They can increase host plant fitness by acquiring soil resources. It is therefore important to determine which measures can be taken to manipulate arbuscular mycorrhizal activities and to apply AM fungi effectively in agriculture. It is well established that functions of AM fungi are subject to the degree of compatibility between fungi and host plant and to the adaptation of AM fungi to edaphic conditions. Thus, in accordance with the INCO-DEV Project requirements, the present study investigated three main aspects of AM fungal isolates screened from northern, central and southern China. Firstly, adaptation and symbiotic efficiency were studied in three major Chinese soil types (Beijing Cinnamon soil, Hubei Brunisolic soil and Guangdong Red soil) in terms of host yield, P uptake and root colonization under glasshouse conditions. Secondly, the responses of effective AM fungi in Beijing Cinnamon soil to severance of extraradical hyphae or different soil P regimes were measured. Thirdly, the performance of selected highly efficient AM isolates and commercial inocula from France in Cinnamon soil was investigated under field conditions in terms of sweet potato yield and quality.All isolates colonized maize and sweet potato in all three soils studied, but their performance in enhancing host yield and P uptake differed significantly. Most isolates colonized and were more effective in soil collected from the region from which they were isolated, but Glomus etunicatum (BEG165) and Glomus geosporaum (BEG151) on Guangdong Red soil and Glomus constrictum (HAU-01) on Hubei Brunisolic soil showed no positive effects on host yield or P uptake. The effectiveness of Glomus mosseae (BEG 167) changed on all three soils when in association with sweet potato instead of maize.Soil ecological adaptation of the isolates was evaluated in terms of extraradical fungal biomass and root colonization. Glomus etunicatum (BEG 168) and Glomus intraradices (BEG 141) were wide-ranging ecotypes, and their fungal biomass was recovered from three soils. Fungal biomass of BEG 168 and BEG151 was collected from two soils. Glomus etunicatum (HAU-E4) and Glomus claroideum (BEG 150) produced fungal biomass on one soil type only, and can therefore be defined as narrow-range ecotypes. Among these isolates BEG168, BEG167, BEG151, HAU-E4 and BEG141 were highly efficient in Beijing Cinnamon soil, and BEG168, BEG167, BEG151, HAU-E4 functioned efficiently in Hubei Brunisolic soil, while only BEG 168, BEG141 and BEG 150 were effective in Guangdong Red soil. The functional efficiency of isolates was related to hyphal P contribution and their P translocation ratio from roots to shoots. The shift in adaptation and symbiotic efficiency of isolates in all three soils was not always consistent. BEG 167, for example, adapted well to all three soils, but had no effect on maize yield or P uptake in Hubei Brunisolic soil. It actually produced negative effects on maize yield and P uptake in Guangdong Red soil. The specific fine root length of maize was significantly correlated with root colonization in association with AM fungal isolates.The application of KH2PO4, Na-phytate and lecithin to the rhizosphere altered the yield and P uptake of maize inoculated with BEG 167 and G. versifrome, but there was no effect on intraradical orextraradical fungal growth. Fertilization with lecithin was more effective than KH2PO4 when maize were inoculated with G. versiforme, while lecithin was less effective than KH2PO4 when maize were inoculated with BEG 167. Maize inoculated with G. versiforme utilized more Na-phytate than maize inoculated with BEG 167.The growth and function of isolates were altered when different P forms and levels were applied to the hyphosphere, while root colonization was unaffected. This indicates that AM fungal growth and function were regulated by soil heterogeneous factors. Four isolates differed in response to P treatments. Fungal biomass of HAU-E4 and BEG 141 changed...
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