Gibberellins and indole-3-acetic acid producing rhizospheric bacterium Leifsonia xyli SE134 mitigates the adverse effects of copper-mediated stress on tomato.

Beneficial bacterialiving in the rhizosphere pose several implications on plant growth promotion and are highly desirable for sustainable agriculture. In the current study, we explored the ameliorative capacity ofLeifsonia xyliSE134, a plant growth-promoting rhizobacteria (PGPR), against copper (Cu) stress on tomato grown under elevated Cu levels of 50 and 100 mM. Initially,L. xyliSE134 modulated innate gibberellins (GAs) and indole-3-acetic acid (IAA) metabolism in response to elevated Cu toxicity. The IAA contents increased, whereas that of bioactive GAs decreased in relation to Cu concentration gradient in the broth media. Furthermore, exposure to elevated Cu caused detrimental effects on the physiological attributes as revealed by attenuated shoot length, root length, stem diameter, shoot dry weight, root dry weight, and chlorophyll content in non-inoculated tomatoes as compared toL. xyliSE134 inoculated plants. The growth rescuing effect ofL. xyliSE134 may be attributed to the modulation of endogenous amino acids contents in plants, such as glutamic acid, threonine, phenylalanine, glycine, proline, and arginine. Moreover,L. xyliSE134 inoculation stimulated total polyphenol and flavonoid content, reduced super oxide dismutase activity, strongly inhibited Cu, and increased phosphorus and iron content in plants grown under elevated Cu stress. In the absence of Cu toxicity,L. xyliSE134 significantly enhanced amino acid content, improved total flavonoids, and increased phosphorus content, thus resulting in higher plant growth. [ABSTRACT FROM PUBLISHER]