Fluorescent pseudomonads: Milestones achieved in the last two decades

Abstract

Environmental concerns have led to the need of sustainable use of natural resources. The conventional agriculture practice caused considerable pollution and unavoidable impacts on soil, water, animal as well as human health. Fluorescent pseudomonads, a group of root-associated bacteria that can colonize the roots of crop plants and produce antifungal metabolites represent a real alternative to the application of chemical fungicides. Fluorescent pseudomonads have been studied for decades for their plant growth-promoting effects through effective suppression of soil borne plant diseases. During root colonization, these bacteria produce antifungal antibiotics that can indirectly suppress fungal pathogens by scavenging iron in the rhizosphere environment through the release of siderophores, elicit induced systemic resistance in the host plant or interfere specifically with fungal pathogenicity factors. Before engaging in these activities, the bacteria go through several regulatory processes at the transcriptional and post-transcriptional levels. Current genomic analyses of rhizosphere competence and biocontrol traits of fluorescent pseudomonads will likely lead to the development of novel tools for effective management of deleterious phytopathogens and a better exploitation of their plant-beneficial properties for sustainable agriculture. This review addresses the main findings on fluorescent pseudomonads for the last two decades. It summarizes and discusses significant aspects of this general topic, including taxonomic status, genetic diversity of fluorescent pseudomonads in India, different mechanisms of biological control and commercial use of fluorescent pseudomonads in agriculture.   Key words: Fluorescent pseudomonads, biological control agent, secondary metabolites, induction of systemic resistance, post-transcriptional regulation.