Chapter 16 - Enhancing the growth and disease suppression ability of Pseudomonas fluorescens

Abstract

Pseudomonas fluorescens is the habitat of soil, water and plant surface. It is a gram-negative, rod-shaped bacterium. It produces a soluble greenish fluorescent pigment called fluorescein, which secretes under low iron conditions. An eco-friendly approach to the control of plant diseases is an emerging need for agriculture in the twenty‐first century. The beneficial rhizobacteria are coming up as an alternative to chemicals at certain extent. Avenues of biological control are plant growth-promoting rhizobacteria (PGPR), which have found potential in preventing phytopathogens causing diseases in plants. The best-characterized biocontrol PGPR belongs to the bacteria genus Pseudomonas. Fluorescent pseudomonads are most suitable in the application of biological control because of their abundant population in soils and plant root system and their capability to utilize many plant exudates as a nutrient. They can adhere to soil particles and also in rhizoplane, motility, synthesis of antibiotics, and production of hydrolytic enzymes. In addition, it also possesses plant growth-promoting traits such as nitrogen fixation, phosphate solubilization, iron chelation, and phytohormone production. The varied utility of P. fluorescens places them at the top most choice to be exploited as a growth promoter and disease suppressor in the field of agriculture. They are producing the substances viz. antibiotics, siderophores, and a spread of enzymes or by induction of systemic resistance in host plants. These microorganisms also can function as competitors of pathogens for nutrition. Antibiotics is one of the important mechanisms used by the biocontrol agent are identified as pyrrolnitrin, pyoluteorin, phenazine, amphisin, 2,4, diacetylphloroglucinol (DAPG), oomycin A, tensin, tropolone, compound and cyclic lipopeptides. The addition of antagonistic antimicrobial producing bacterial strains, either individually or as a mixture in combination with fungicide, significantly decreased the plant disease stress. The present chapter refers to the occurrence, distribution, mechanism of biocontrol against many diseases of agriculture and horticultural crops.