Growth stimulation of subterranean clover with vesicular arbuscular mycorrhizas

Abstract

The growth of subterranean clover inoculated with two types of vesicular arbuscular endophytes was compared with that of uninoculated plants at five levels of applied superphosphate in a high phosphatefixing soil. Plants were grown in both untreated soil and soil steamed to eliminate the natural population of mycorrhizal fungi. Marked increases in the growth and phosphorus content of plants inoculated with a fungus isolated in Western Australia were apparent at intermediate levels of superphosphate in both soils. This fungus, which resembles Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, was more efficient at increasing growth and phosphorus content of subterranean clover than Glomus fasciculatus (Thaxter) Gerd. & Trappe. The greater growth response of plants inoculated with the fungus resembling G. mosseae was associated with a greater amount of mycorrhizal roots. Responses in nodulation closely paralleled responses in growth. Non-mycorrhizal plants produced more dry matter at a given phosphorus concentration in tops than did mycorrhizal plants.