The role of endophytic salt-tolerant Franconibacter Sp. YSD YN2 in Cyperus esculentus L. Var sativus: impacts on plant growth and mechanisms of salt tolerance.

BACKGROUND CYPERUS ESCULENTUS

L. var. sativus (chufa) is a perennial plant known for its nutrient-rich underground tubers and aboveground leaves, which offer significant food and health advantages worldwide. Despite its benefits, salt stress hinders plant growth, thus limiting both yield and quality. While the positive effects of plant growth-promoting endophytes (PGPEs) on plant growth have been established, their particular influence on chufa under salt stress has yet to be investigated. This research focused on examining the principal physiological and metabolic responses of chufa following inoculation with the PGPE Franconibacter sp. YSD YN2 at varying NaCl concentrations.

RESULTS

YSD YN2 exhibited significant salt resistance, robust colonization of plant compartments, and various characteristics (indole-3-acetic acid (IAA) (0.90-14.74 µg/mL), phosphate (P) (0.00-20.00 µg/mL), potassium (K) solubility (1.00-2.50), and exopolysaccharides (EPSs) (0.80-28.09 mg/mL)) under different NaCl concentrations, underscoring its capacity to enhance plant development and recuperation under salt stress. YSD YN2 inoculation significantly enhanced plant growth across different NaCl concentrations, including improvements in shoot height (13.33-26.67%), shoot weight (48.91-115.38%), root length (7.84-13.17%), root weight (39.43-63.06%), relative water content (1.78-10.80%), and the number of tillers (50.00-183.50%). Inoculation with YSD YN2 resulted in increased total chlorophyll contents (25.30-83.57%), improved efficiency of antioxidant enzymes such as peroxidase (POD) (13.81-35.48 fold), superoxide dismutase (SOD) (10.67-13.34%), and catalase (CAT) (25.00-78.95%), diminished malondialdehyde (MDA) accumulation (14.10-31.19%), and increased proline accumulation (11.37-19.64%) in chufa. Additionally, inoculation with YSD YN2 led to a reduction in internal Na accumulation and an increase in K and Ca absorption.

CONCLUSION

YSD YN2 may serve as a valuable PGPE for improving plant development, photosynthetic pigmentation, oxidative processes, and osmotic control substances, controlling ion absorption, and reducing the harmful impacts of high-salinity chufa.