Mycorrhizal fungi effects on nutrient composition and yield of soybean seeds

Abstract

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.