Nodulating associations among rhizobia and legumes of the genus Glycine subgenus Glycine

Glycine canescens, G. tabacina, and G. tomentella were used to trap rhizobia from American soils. Rhizobia recovered from these nodules then were compared with isolates from plants that had been naturally nodulated in Australia. All isolates were mucoid and gave alkaline reactions on yeast extract-mannitol medium. Two American isolates from G. tabacina were noticeably stringy. The nodulating abilities of 13 isolates, including four from Australia, were examined. All nodulated Aeschynomene americana, Vigna unguiculata, and Macroptilium atropurpureum. With one exception, each isolate also nodulated all three Glycine spp. Tests with a series of slow-growing reference strains suggest that G. tomentella nodulates more promiscuously than G. tabacina and G. canescens. All three plant species are infected via infection threads produced in short, curled root hairs.