Indole-3-Acetic Acid and 1-Aminocyclopropane-1-Carboxylate Deaminase: Bacterial Traits Required in Rhizosphere, Rhizoplane and/or Endophytic Competence by Beneficial Bacteria

Abstract

Majority of plants harbor a diverse community of bacteria, which can positively affect host plant growth. Plant-associated bacteria have various plant growth-promoting (PGP) traits. Rhizobacteria are PGP bacteria within rhizosphere that can enhance plant growth by a wide variety of mechanisms like production of phytohormones, siderophore, 1-aminocyclopropane-1-carboxylate (ACC) deaminase and volatile organic compounds, phosphate solubilization, biological nitrogen fixation, rhizosphere engineering, quorum sensing signal interference and inhibition of biofilm formation, exhibiting antifungal activity, induction of systemic resistance, promoting beneficial plant–microbe symbioses and interference with pathogen toxin production. In recent years, interest in the use of plant growth-promoting rhizobacteria (PGPRs) to promote plant growth has increased. The use of PGPRs has steadily increased in agriculture and offers an attractive alternative to replace chemical fertilizers, pesticides and supplements. To act as PGPRs, any bacteria should be able to colonize and survive in the rhizosphere of plants. A competent colonization is essential for PGP effects produced by the bacteria and the important first step in the interaction of bacteria with plants. The purpose of this review was to give an overview on the most important PGP traits involved in plant more colonization. It seems that PGP traits of production of IAA and ACC deaminase may be required for endophytic and rhizosphere competence by PGPRs. In addition, this review indicates that the selected bacterial isolates based on their IAA and ACC deaminase-producing traits have the potential for more colonization of plants. Such bacteria may be used for a sustainable crop management under field conditions. Bacterial IAA together with ACC deaminase increase root surface area and length, and thereby provide the plant to have greater access to soil nutrients under different environmental conditions including stress situations. Therefore, proper screening of PGPRs can be useful for future agricultural applications, providing higher production yields, reduced input costs and negative environmental impact due to the use of chemical fertilizers.