Isolation and evaluation of growth-promoting endophytic bacteria from Zanthoxylum dissitum Hemsl

The slow growth rate of Zanthoxylum dissitum Hemsl. (Zanthoxylum) is the important factor causing the scarcity of its available wild resource. It has been reported that the plant endophytes can promote the plant growth and the synthesis of secondary metabolitesby by enhancing the efficiency of nutrient absorption by plants and regulating plant hormones. It is important to explore the promoting effects of endophytes on the growth of Zanthoxylum. The application of high-throughput sequencing technology in this study revealed the presence of three phyla, five classes, seven orders, and eleven genera of endophytic bacteria in Zanthoxylum. The most prevalent phyla, classes, orders, and genera were identified respectively as Proteobacteria, Gammaproteobacteria, Burkholderiales, and Pseudomonas. In this study, an endophytic growth-promoting bacterium was isolated and identified as Sphingomonas sp. The results revealed that the bacterium exhibited robust nitrogen fixation, phosphorus solubilization, and effective siderophore production capabilities. The phosphate solubilization index (SI) was found to be (1.266 ± 0.0157). Following a 48-h incubation period in an inorganic phosphorus liquid medium (PKO), the concentration of auxin (IAA) and gibberellin (GA) reached their highest levels, at (138.145 ± 65.111) μg/mL and (805.74 ± 123.86) μg/mL, respectively. Moreover, the study showed that the endophytic bacteria markedly enhanced the germination potential and rate of sorghum seeds, and promoted significantly the growth of the tissue culture seedlings of Zanthoxylum.