Isolation of Nitrogen-Fixing Bacteria from Water Yam (Dioscorea alata L.)

Abstract

The results of our previous experiment showed that water yam (Dioscorea alata L.) was able to grow under low fertility soil conditions without nitrogen fertilization. Moreover, changing δ¹⁵N values suggested that nitrogen is absorbed from the air. The objective of this study, therefor, was to confirm and identify the nitrogen-fixing bacteria in water yam plants. The nitrogen fixation ability of isolated bacteria was measured using the acetylene reduction assay in semi-solid nitrogen free medium. Phylogenetic analysis of 16S rRNA gene sequences revealed nine genera in the stems and roots. These isolates were shown to be related to genus Bacillus, Cohnella, Rhizobium, Kosakonia, Azospirillum, Pantoea, Dyella, Enterobacter, and Ralstonia. This is the first result that NFB were isolated from water yam plant cultivated under low soil fertility condition at Miyako Island, Japan.