11.SYNTHETIC PLANT ACTIVATORS FOR CROP DISEASE MANAGEMENT By SREEJA_ S.J.

Abstract

In a resistant cultivar, the defense system of the host is activated properly in time and to a sufficient magnitude necessary to suppress the advancement of the pathogen resulting in decreased or no disease. Whereas in a susceptible cultivar, in spite of the presence of general defense genes, are unable to block the advancement of the pathogen and disease development, since these are activated either late or their magnitude of expression is of a lower amount. However, with the use of certain biotic or abiotic defense inducers even susceptible cultivars can be made resistant by activating their disease defense response system. Plant activators are chemicals that activate the defense genes in plants by providing signals via the signal transduction pathway mediated by salicylic acid. Since plant activators do not have any pesticidal or antibiotic activity, their adverse effects on human health and environment are minimal. In addition, since they do not interact directly with the pathogens, it is unlikely that plant pathogens will develop resistance to these chemicals. Among the plant activators, important ones are acibenzolar-S-methyl, 2, 6-dichloroisonicotinic acid, ?-aminobutyric acid, probenazole, salicylic acid, riboflavin, prohexadione- Ca, potassium phosphonate, harpin and methyl jasmonate. The success of defense inducers for plant disease control depends on our ability to manage their phytotoxicity either by chemical modification of the compound or by modifying their formulation. Since, plant activators would never be able to provide complete protection; they could be more suited as a component of integrated disease management.

KEYWORDS: Plant activators, Systemic acquired resistance, Signal transduction, Induced systemic resistance, Defense response.