Genetic diversity and promotion plant growth of culturable endophytic diazotrophs associated with seashore paspalum cultivars

Turfgrass lawns demand high inputs of nitrogen (N) to maintain attractive and functional landscapes. Endophytic diazotrophs have a high potential to increase N in the host plant and promote growth by biological N fixation. The aim of this study was to identify the genetic diversity of culturable putative diazotrophs associated with seashore paspalum (Paspalum vaginatum Swartz) cultivars in southern China. A total of 78 isolates were collected from the roots, stems and leaves of healthy plants. A phylogenetic analysis showed that all the isolates were classified into 10 species from nine genera. The dominant genera were Bacillus, followed by Curtobacterium and Stenotrophomonas. The population of diazotrophs in the roots was more diverse than that in the stems and leaves. The 10 representative strains were found to be positive for nitrogenase activity and amplification of the nifH gene, and nine strains could solubilise inorganic phosphate. In addition, two isolates of bacteria, Bacillus pumilus and Lysinibacillus macrolides, were selected to evaluate the promotion of plant growth by inoculation. Ryegrass and rice plants inoculated with bacteria displayed significantly greater root and shoot biomass than un-inoculated plants. It is crucial to further explore their potential roles in the biology of these plants.