Influence of the plant growth promoting Rhizobium panacihumi on aluminum resistance in Panax ginseng

Abstract

Background: Panax ginseng is an important crop in Asian countries given its pharmaceutical uses. It is usually harvested after 4–6 years of cultivation. However, various abiotic stresses have led to its quality reduction. One of the stress causes is high content of heavy metal in ginseng cultivation area. Plant growth–promoting rhizobacteria (PGPR) can play a role in healthy growth of plants. It has been considered as a new trend for supporting the growth of many crops in heavy metal occupied areas, such as Aluminum (Al). Methods: In vitro screening of the plant growth promoting activities of five tested strains were detected. Surface-disinfected 2-year-old ginseng seedlings were dipping in Rhizobium panacihumi DCY116T suspensions for 15 min and cultured in pots for investigating Al resistance of P. ginseng. The harvesting was carried out 10 days after Al treatment. We then examined H2O2, proline, total soluble sugar, and total phenolic contents. We also checked the expressions of related genes (PgCAT, PgAPX, and PgP5CS) of reactive oxygen species scavenging response and pyrroline-5-carboxylate synthetase by reverse transcription polymerase chain reaction (RT-PCR) method. Results: Among five tested strains isolated from ginseng-cultivated soil, R. panacihumi DCY116T was chosen as the potential PGPR candidate for further study. Ginseng seedlings treated with R. panacihumi DCY116T produced higher biomass, proline, total phenolic, total soluble sugar contents, and related gene expressions but decreased H2O2 level than nonbacterized Al-stressed seedlings. Conclusion: R. panacihumi DCY116T can be used as potential PGPR and “plant strengthener” for future cultivation of ginseng or other crops/plants that are grown in regions with heavy metal exposure.

Keywords

• Aluminum resistance
• Aluminum stress
• Panax ginseng
• Plant growth–promoting rhizobacteria
• Rhizobium panacihumi