A Growth-Promoting Bacteria, Paenibacillus yonginensis DCY84(T) Enhanced Salt Stress Tolerance by Activating Defense-Related Systems in Panax ginseng

Panax ginseng (C.A. Mayer) is a well-known medicinal plant used in traditional medicine in Korea that experiences serious salinity stress related to weather changes or incorrect fertilizer application. In ginseng, the use of Paenibacillus yonginensis DCY84(T) to improve salt stress tolerance has not been thoroughly explored. Therefore, we studied the role of P. yonginensis DCY84(T) under short-term and long-term salinity stress conditions in a controlled environment. In vitro testing of DCY84(T) revealed high indole acetic acid (IAA) production, siderophore formation, phosphate solubilization and anti-bacterial activity. We determined that 10-min dip in 10(10) CFU/ml DCY84(T) was sufficient to protect ginseng against short-term salinity stress (osmotic stress) upon exposure to 300 mM NaCl treatment by enhancing nutrient availability, synthesizing hydrolyzing enzymes and inducing osmolyte production. Upon exposure to salinity stress (oxidative and ionic stress), strain DCY84(T)-primed ginseng seedlings were protected by the induction of defense-related systems such as ion transport, ROS scavenging enzymes, proline content, total sugars, and ABA biosynthetic genes, as well as genes involved in root hair formation. Additionally, ginseng primed with DCY84(T) and exposed to 300 mM NaCl showed the same metabolite profile as control ginseng plants, suggesting that DCY84(T) effectively reduced salt stress. These results indicated that DCY84(T) can be widely used as a microbial inoculant to protect ginseng plants against salinity stress conditions.