Secondary Metabolites of Pseudomonas aurantiaca and Their Role in Plant Growth Promotion

Abstract

t Most of the fl uorescent pseudomonads isolated from plant rhizosphere promote plant growth by direct and indirect mechanisms. These bacteria produce phytohormones and promote plant growth directly. In addition, they produce sec ondary metabolites which inhibit the growth of pathogenic bacteria and fungi and promote plant growth indirectly. Among fl uorescent pseudomonads, Pseudomonas aurantiaca , a subspecies of Pseudomonas chlororaphis , is known to produce anti biotics with antifungal activity. Strains of P . aurantiaca have been isolated from sugarcane, soya bean, canola, soil, and municipal sludge in different parts of the world including North America, Europe, and Asia. These strains are reported to produce IAA, HCN, siderophores, phenazines, cyclic lipopeptides, pyoverdin, and quorum-sensing signaling compounds. Most of these strains have shown antifungal activity against several pathogenic strains of Fusarium , Pythium , Colletotrichum , Rhizoctonia , and Sclerotium sp. One of these P . aurantiaca strain SR1 has been proven as a plant growth promoter for several crops. In this manuscript, a review of all reported strains of P . aurantiaca and their growth-promoting abilities is presented. The main focus is on secondary metabolites and mechanism used by these meta bolites to promote plant growth, with a suggestion that this bacteria can be used as a biofertilizer and a biocontrol agent in the near future.