Induction of Systemic Resistance in Crop Plants Against Plant Pathogens by Plant Growth-Promoting Actinomycetes
Plants possess the ability to acquire and express an enhanced defense mechanism against pathogen attack after being treated with biocontrol agents or chemical stimulant. The role of induced systemic resistance by biocontrol agents against pathogen coloniz
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Induction of Systemic Resistance in Crop Plants Against Plant Pathogens by Plant Growth-Promoting Actinomycetes G. Senthilraja
Abstract
Plants possess the ability to acquire and express an enhanced defense mechanism against pathogen attack after being treated with biocontrol agents or chemical stimulant. The role of induced systemic resistance by biocontrol agents against pathogen colonization has been revealed in several crop plants. Actinomycetes are one of the most promising sources of biocontrol agents at present gaining increased attention in the field of biological control. The secondary metabolites produced by actinomycetes play a vital role in plant growth promotion as well as suppression of pathogen growth and development in host plant. In this chapter, traits involved in plant growth-promoting actinomycetes (PGPA)-mediated induced systemic resistance (ISR) will be discussed. Keywords
Induced systemic resistance • Actinomycetes • Endophytes • Biological control • Plant pathogens
12.1
Introduction
Plant disease management is done mainly by means of chemicals. Various chemical pesticides have been reported to be effective against a wide range of pathogens but not considered as long-term solution because of concerns about health and environmental hazards, expensiveness, residue persistence, G. Senthilraja (*) Centre of Excellence in Millets, Tamil Nadu Agricultural University, Athiyandal, Tiruvannamalai 606 603, Tamil Nadu, India e-mail: [email protected]
pest resurgence, and elimination of natural enemies. Therefore, the need for alternative method of control of plant diseases has become vital. The development of biological control for plant diseases is accepted as a durable and eco-friendly alternative for agrochemicals. Beneficial microorganisms either bacteria or fungi that survive in the plant rhizosphere region exhibit direct and/or indirect mechanism as plant growth promoters and biocontrol agents. Direct mechanisms include making the availability of phosphorus for plant uptake, nitrogen fixation, production of siderophores and plant growth hormones such as auxins, cytokinins,
# Springer Science+Business Media Singapore 2016 G. Subramaniam et al. (eds.), Plant Growth Promoting Actinobacteria, DOI 10.1007/978-981-10-0707-1_12
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and gibberellins, and lowering plant ethylene levels using 1-aminocyclopropane-1-carboxylate (ACC) deaminase that accumulated during biotic and abiotic stresses (Glick 1995; Mayak et al. 2004). Indirect mechanisms include the production of antibiotics, viz., 2,4-diacetylphloroglucinol (DAPG), phenazine, pyoluteorin, and pyrrolnitrin against pathogens, reduction of iron availability to phytopathogens in the rhizosphere, synthesis of cell wall-lysing enzymes, competition with harmful microbes for space in the rhizosphere region, and induction of systemic resistance (Ramamoorthy et al. 2001). Among several other modes of actions, induced resistance is one of the promising mechanisms by which the beneficial microbes including endophytes restrict the pathogen g
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