Antarctic rhizobacteria improve salt tolerance and physiological performance of the Antarctic vascular plants

The two native Antarctic vascular plants, Deschampsia antarctica and Colobanthus quitensis, are mostly restricted to coastal habitats where they are often exposed to sea spray with high levels of salinity. Most of the studies regarding the ability of C. quitensis and D. antarctica to cope with abiotic stress have been focused on their physiological adaptations to tolerate cold stress, but little is known about their tolerance to salinity. We investigated whether rhizospheric bacteria associated to D. antarctica and C. quitensis improve the ability of Antarctic plants to tolerate salt stress. Salt tolerance was assayed in rhizospheric bacteria, and also their effects on the ecophysiological performance (photochemical efficiency of PSII, growth, and survival) of both plants were assessed under salt stress. A total of eight bacterial rhizospheric strains capable of growing at 4 °C were isolated. The strains isolated from D. antarctica showed higher levels of salt tolerance than those strains isolated from C. quitensis. The ecophysiological performance of C. quitensis and D. antarctica was significantly increased when plants were inoculated with rhizospheric bacteria. Our results suggest that rhizospheric bacteria improve the ability of both plants to tolerate salinity stress with positive effects on the adaptation and survival of vascular plants to current conditions in Antarctic ecosystem.