ABSTRACT
ABSTRACT Plant growth-promoting rhizobacteria (PGPR) are rhizosphere-colonizing bacteria that improve plant growth and development through various mechanisms such as improvement of plant nutrition, protection of plants from various pathogens, induction of plant host-defense mechanisms, and others. In agricultural production systems, plant pathogens-particularly fungi, bacteria, viruses, and mycoplasmas-cause severe economic losses. Traditionally, plant diseases are managed by synthetic chemicals that escalate the cost of production and contaminate the environment with their toxic residues. Therefore, alternative methods for the control of plant pathogens have become vital. Among the many available disease-control strategies, the use of microbes is considered to be green and eco-friendly. Although the bio-control of plant pathogens was initiated in the 1920s, the rst commercial bacterial biocontrol agent (Agrobacterium radiabacter 84) was not introduced until the early
14.1 Introduction .......................................................................................................................... 274 14.2 Plant Pathogenic Bacteria ..................................................................................................... 275 14.3 PGPR and Their Mechanisms of Biocontrol ........................................................................ 275
14.3.1 Antagonistic Activity ................................................................................................ 275 14.3.2 Siderophore Production ............................................................................................ 279 14.3.3 Hydrogen Cyanide Production ..................................................................................280 14.3.4 Detoxication of Pathogen Virulence Factors ..........................................................280 14.3.5 Induced Systemic Resistance ....................................................................................280
