Plant–bacteria interaction under saline stress: The Tabebuia aurea–Methylobacterium system

Abstract

Tabebuia aurea is a tree with anti-inflammatory, analgesic, and anti-ophitic properties in traditional medicine. Also, it is a timber resource and an ornamental plant. In previous experiments, we could not carry out in vitro micropropagation of T. aurea free of an endophytic bacterium (named TA1). Moreover, we observed that TA1 association was necessary to proliferate T. aurea in vitro culture. It has been described that some of these kinds of microorganisms can promote plant growth and alleviate harmful effects of abiotic stress like salinity by producing a wide range of compounds such as phytohormones, enzymes, and by improving nutrient acquisition, among others. This work aimed first to isolate and characterize the TA1 strain and then evaluate the effect of saline stress, induced by NaCl and Na2SO4, on growth parameters during in vitro rooting of the T. aurea - TA1 system. The TA1 strain was identified as Methylobacterium and exhibited plant growth-promoting bacteria (PGPB) traits, such as nitrogen fixation and phosphate solubilization, and indole compound production, such as IAA (indoleacetic acid). The inhibitory concentration of 50 % rooted plants (IC50) was further reduced by the sulfate (SO4−2) anion than by the chloride (Cl−) anion. m sp. Although increased NaCl and Na2SO4 concentrations reduced the rooting percentage, the growth parameters, and the biometric parameters index in the Tabebuia aurea - Methylobacterium system, this system proved to be tolerant to Na+ considered highly saline or sodium-saline concentrations.