Ecological roles of arbuscular mycorrhizal fungi in two wild legume plants

Two wild legume plants, Glycine soja and Cassia mimosoides var. nomame, and a cultivated plant, soybean (Glycine max), were employed for a study of triple symbiosis with an inoculum of Scutellispora heterogama harvested from natural soils and an inoculum of their own rhizobial cells. The dry weight, colonization of arbuscular mycorrhizal fungus, nodule formation and N2-fixation activity were estimated as the parameters of triple symbiosis. The two wild legume plants showed greater growth with colonization of arbuscular mycorrhizae than with nodulation, whereas the cultivated legume showed more nodulation than colonization of arbuscular mycorrhizae. Moreover, S. heterogama appeared to stimulate the triple symbiosis for the wild legume plants. The results suggested that spores of S. heterogama are important in disturbed soils in Korea.