AUTHOR=Liu Guohua , Liu Xiaoling , Liu Wei , Gao Kangning , Chen Xiaoli , Wang En-Tao , Zhao Zhenjun , Du Wenxiao , Li Yan 

TITLE=Biodiversity and Geographic Distribution of Rhizobia Nodulating With Vigna minima

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.665839

DOI=10.3389/fmicb.2021.665839

ISSN=1664-302X

ABSTRACT=<p><italic>Vigna minima</italic> is a climbing annual plant widely distributed in barren wilderness, grass land, and shrub bush of China and other countries such as Japan. However, the rhizobia nodulating with this plant has never been systematically studied. In order to reveal the biodiversity of nodulating rhizobia symbiosis with <italic>V. minima</italic>, a total of 874 rhizobium isolates were obtained from root nodules of the plant spread in 11 sampling sites of Shandong Peninsula, China, and they were designated as 41 haplotypes in the genus <italic>Bradyrhizobium</italic> based upon <italic>recA</italic> sequence analyses. By multilocus sequence analysis (MLSA) of five housekeeping genes (<italic>dnaK</italic>, <italic>glnII</italic>, <italic>gyrB</italic>, <italic>recA</italic>, and <italic>rpoB</italic>), the 41 strains representing different <italic>recA</italic> haplotypes were classified into nine defined species and nine novel genospecies. <italic>Bradyrhizobium elkanii</italic>, <italic>Bradyrhizobium ferriligni</italic>, and <italic>Bradyrhizobium pachyrhizi</italic> were the predominant and universally distributed groups. The phylogeny of symbiotic genes of <italic>nodC</italic> and <italic>nifH</italic> showed similar topology and phylogenetic relationships, in which all the representative strains were classified into two clades grouped with strains nodulating with <italic>Vigna</italic> spp., demonstrating that <italic>Vigna</italic> spp. shared common nodulating groups in the natural environment. All the representative strains formed nodules with <italic>V. minima</italic> in a nodulation test performed in green house conditions. The correlation between <italic>V. minima</italic> nodulating rhizobia and soil characteristics analyzed by CANOCO indicates that available nitrogen, total nitrogen, and organic carbon in the soil samples were the main factors affecting the distribution of rhizobia isolated in this study. This study systematically uncovered the biodiversity and distribution characteristics of <italic>V. minima</italic> nodulating rhizobia for the first time, which provided novel information for the formation of the corresponding rhizobium community.</p>