Diversity and infectivity of arbuscular mycorrhizal fungi in agricultural soils of the Sichuan Province of mainland China.

Knowledge about the presence and diversity of arbuscular mycorrhizal fungi (AMF) in a specific area is an essential first step for utilizing these fungi in any application. The community composition of AMF in intensively managed agricultural soil in the Sichuan Province of southwest China currently is unknown. In one set of samples, AMF were trapped in pot cultures from 40 fields growing legumes in the Panxi region, southeast Sichuan. In a second set of samples, the MPN method with four-fold dilutions and maize as host was used to estimate infective propagules in soil from another 50 agricultural sites throughout the province. Soil types were heterogeneous and were classified as purple, yellow, paddy and red. Crops at each site were either maize, wheat or sweet orange. From this set of soil, AMF spores were also extracted and identified. Including all ninety soils, thirty glomeromycotan species in Glomus (20 species), Acaulospora (four species), Scutellospora (three species), Ambispora (one species), Archaeospora (one species) and Paraglomus (one species) were identified. Yellow, red and purple soils yielded similar numbers of AMF species, while AMF species diversity was clearly lower in paddy soil. In trap culture soils, the most frequent species were Glomus aggregatum or Glomus intraradices, Glomus claroideum and Glomus etunicatum. The species Acaulospora capsicula, Acaulospora delicata, G. aggregatum (or intraradices), G. claroideum, Glomus epigaeum, G. etunicatum, Glomus luteum, Glomus monosporum, Glomus mosseae and Glomus proliferum were successfully cultured as single-species pot cultures in Plantago lanceolata. The three most frequent species in field soils were G. mosseae, Glomus caledonium and Glomus constrictum. MPN values varied between 17 and 3334 propagules 100 g soil(-1) among the fifty field sites sampled. Regression analysis, including host&soil, log(P) and pH as explanatory variables explained 59% of the variation in log(MPN). The highest MPN estimates were found in purple soil cropped with maize and citrus, 324 and 278 propagules 100 g soil(-1), respectively. The lowest MPN value, 54 propagules 100 g soil(-1), was measured in wheat in purple and yellow soil. Despite intensive agricultural management that can include often repeated tillage, our examination of 90 agricultural sites revealed that soils of the Sichuan region have moderate to high numbers of infective AMF propagules as well as a high AMF species diversity. This opens possibilities for further studies and utilization of AMF in agriculture and horticulture in the Sichuan province, People's Republic of China.