Diversity and efficacy of arbuscular mycorrhizal (AM) fungi isolated from soils of soybean fields.

摘要

A field survey evaluated the population composition of AM fungal species in Clarion (a well drained fine-loamy, mixed, mesic Typic Hapludoll) and Webster (a poorly drained fine-loamy, mixed, mesic Typic Endoaquoll) soils of four Iowa soybean (Glycine max, L.) fields. Spores from six species of Glomus and from the genera Acaulospora, Gigaspora , and Paragomus were found in the original field soils. G. claroideum, G. etunicatum, G. mosseae, G. viscosum, and Paraglomus occultum-like spores were prevalent in both Clarion and Webster soils of all four fields. Minor species included G. geosporum and G. intraradices. Trap cultures led to detection of several additional AM fungal species, including G. clarum, G. constrictum, G. fasciculatum, and Entrophospora infrequens.; The selectivity of four soybean cultivars, BSR201, Iowa2052, Mandarin, and Peking, for AM fungi was assessed in pots inoculated with composite soil samples from Clarion and Webster soils. A total of 12 morphotypes of AM fungal species were identified. Pots of Iowa2052 soybean cultivar harbored all 12 AM fungal species. Spores of E. infrequens were found uniquely in Iowa2052 pots. Peking had only 8 different types of AM fungi. G. claroideum produced a high proportion of the spore population in pots of BSR201 (up to 75%), but this species was low in Peking (2 to 12%) when the inocula were derived from Webster soils.; Soybean cultivars BSR201, Iowa2052, and Peking inoculated with five strains of G. claroideum, two strains of G. etunicatum, and one strain of G. mosseae obtained from Clarion and Webster soils of two Iowa fields produced significantly higher shoot dry weights and seed numbers per pot than those that were nonmycorrhizal. The efficacy of the isolates on the growth of inoculated 10-wk-old plants depended on both the host cultivar and the infecting AM fungal strain. Isolates of G. claroideum and G. etunicatum originally from Clarion soils typically increased shoot dry weight more than did the isolates of either G. etunicatum or G. mosseae from Webster soil. Isolates of G. claroideum and G. etunicatum generated higher dry weight in Peking plants than in the plants of the other two cultivars.