Abstract
The potential of sweet potato to benefit from biological nitrogen fixation has been reported. In this study, culture-independent method based on the direct PCR amplification of nitrogenase gene (nifH) was applied to obtain information on the endophytic nitrogen-fixing bacteria in sweet potato. Genomic DNA and RNA from the leaf, petiole, stem and tuber samples of field-grown sweet potato were extracted. The fragments of nifH gene were amplified with two sets of degenerate primers by nested-PCR. The DNA sequence with high similarity to the nifH gene from Bradyrhizobium japonicum and Paenibacillus azotofixans were found in petiole, Anabaena variabilis, Herbaspirillum seropedicae, A. 7120 and Nostoc commune were found in stem, and Rhizobium leguminosarum and B. japonicum were found in tuber. RT-nested-PCR analysis revealed that the clones homologous to Bradyrhizobium sp. and uncultured N2-fixing bacterium were expressed in stem, and clones homologous to uncultured N2-fixing bacterium was expressed in tuber.
