The Endophytic Symbiont—Pseudomonas aeruginosa Stimulates the Antioxidant Activity and Growth of Achyranthes aspera L.

Abstract

A plant growth promoting bacterial endophyte designated as AL2-14B isolated from the leaves of <i>Achyranthes aspera</i> L. was identified as <i>Pseudomonas aeruginosa</i> based on its phenotypic and physiological features, and 16S rRNA gene sequence analysis. AL2-14B had plant growth stimulating attributes including siderophore and indole acetic acid release, inorganic phosphate solubilization, along with nitrogenase, ammonification, and protease activities. It also exhibited antifungal property against <i>Rhizoctonia solani</i>. The plantlets grown in germ-free condition were inoculated with AL2-14B and studied for the colonization of endophyte. Significant increase in population of AL2-14B between 3rd and 5th days after inoculation was recorded. The treatment of plants with endophytic <i>P. aeruginosa</i> AL2-14B increased nitrogen, phosphorus, potassium (NPK) contents in plant by 3.8, 12.59, and 19.15%, respectively. Significant enhancement of shoot and root length, dry leaf, dry shoot and dry root weight, and leaf surface area as compared to control (<i>P</i> < 0.05) was recorded in AL2-14B inoculated plants. The antioxidant activities increased in plants grown in germ-free conditions and inoculated with AL2-14B. The present study emphasizes on the role of diazotrophic endophyte <i>P. aeruginosa</i> AL2-14B in stimulating growth of <i>A. aspera</i> L. and improvement of its medicinal properties. Significant increase in growth and antioxidant content of <i>P. aeruginosa</i> AL2-14B treated plants suggests the possibility of an economical and eco-friendly mean of achieving antioxidants rich, healthier <i>A. aspera</i> plants.