Enhancing the growth performance of Sesbania cannabina using Ensifer alkalisoli and biochar under salt stress

Sesbania cannabina is a leguminous salt-tolerant plant that has been effectively used in saline-alkaline land restoration, and forms symbiotic interactions with various rhizobia to form nodules. Ensifer alkalisoli YIC4027, a rhizobium, was screened from S. cannabina root nodules and has significant host specificity. However, the mechanism underlying the symbiotic salt tolerance of S. cannabina -YIC4027, and strategies to enhance this tolerance remain poorly understood. In this study, the mechanism underlying the effect of YIC4027 on the salt tolerance of S. cannabina and the effect of straw biochar on the symbiotic nodulation of S. cannabina-YIC4027 under salt stress were analyzed using a vermiculite pot test. The results indicated that inoculation with YIC4027 markedly increased the biomass, chlorophyll content, photosynthetic rate, superoxide dismutase (SOD) activity and catalase (CAT) activity of S. cannabina under salt stress, while there was no obvious change in glutathione (GSH) or proline (PRO) content. The nitrogen supply and salt concentration are important regulators of YIC4027 nodulation. Salt stress reduced the nodulation efficiency of YIC4027 by 66.67%, and straw biochar application resulted in a 5-fold increase in nodulation efficiency of YIC4027. The present results further suggest that the combination of YIC4027 and straw biochar is an effective biological method for enhancing the effectiveness of S. cannabina in saline-alkali soil improvement.