Mycorrhizal fungi effects on nutrient composition and yield of soybean seeds

Nutrient composition and yield of soybean [Glycine max (L.) Merr] seeds are heritable traits affected by environmental factors. This study determined the effects of arbuscular-mycorrhizal (AM) fungi on seed protein, lipid, and phosphorus (P) composition and yield in soybean grown under a high nitrogen (N) regime. Plants were grown in pot cultures without AM fungi in P-fertilized (+P) or unfertilized (-P) soil, or in -P soil inoculated with one of the AM fungi Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe (Gm), Glomus etunicatum Becker and Gerd.(Ge), or Gigaspora rosea Nicol. and Schenck (Gr). Seed yields of +AM plants, as a group, were halfway between those of the +P and -P plants. Seed size was highest in Gm plants. Differences in protein concentrations between Ge and Gr and the other treatments were highly significant. Seed P and protein concentrations were not significantly correlated (p=0.162), but a highly significant (r=-0.949) negative correlation between seed P and lipid concentrations was observed. Phosphorus concentration was highest and that of lipids lowest in +AM plants. Seed yield and nutrient composition were independent of the intensity of root colonization. The seed protein/lipid ratio was highly correlated with seed P concentration and was significantly higher for +AM plants, as a group, than for both +P and -P -AM plants. Differences in seed dry weight, size, seed/stem ratio, P content, and protein concentration among +AM plants showed mycorrhiza-specific host responses. These responses suggest that AM fungi can modify soybean seed development and chemical composition.