Novel finding of Paulownia fortunei endophytic rhizobia in China

Previous research has mainly focused on breeding, timber supply, and
physiological-biochemical characteristics of Paulownia fortunei. However,
there has been limited attention given to its endophytic rhizobia and its
potential benefits for plant growth due to a lack of knowledge about the
existence of root nodules. In this study, we extracted 9
bacterial strains from the root nodules after occasionally discovering the
nodular-like structure in uncultivated 3-year P. fortunei roots and then
sequenced the 16S rDNA and nifA sequencing to conduct the bacterial strain
identifications. We then determined the carbon use capability and
nitrogenase activity of the bacterial strains. The result of 16S rDNA
sequencing indicated that the endophytic rhizobia belongs to the genus
Agrobacterium, Rhizobium, Herbaspirillum, and Burkholderia. The results of
nifA sequencing indicated that the nifA gene was sequenced in strain PG-3,
PG-5, PG-6, PG-7, PG-8, rather than in strain PG-1, PG-2, and PG-4.
Besides, the nitrogenase activity of strain PG-9 was significantly higher
than other bacterial strains. RDA results indicated that
fructose, glucose, and sucrose were significantly related to the plant
height, diameter, and biomass rather than other carbon sources and
nitrogenase activity. Our research revealed that the majority of bacterial
strains isolated from P. fortunei exhibited a broad carbon utilization
pathway and have the potential to promote plant growth after
re-Inoculation. This study aims to investigate the phylogeny of endophytic
rhizobia in P. fortunei, and expand the range of non-legume hosts studied
for future research on biological N fixation.