natural-products-in-plant-pest-management

Control of Virus Diseases of Plants 153activity after 48 h of its application in N. glutinosa. Thus, VIA production in ahost is time specific but a general phenomenon. Properties of VIA producedin C. tetragonoloba after application of B. spectabilis leaf extract has been studiedby Verma and Dwivedi (1984). The VIA could be precipitated by ammoniumsulfate and hydrolysed by trypsin but not by ribonulease indicatingthat it was a protein rather than a nucleic acid. The VIA induced by Pseuderanthemumbicolor in C. tetragonoloba was also proteinaceous with a molecularweight of 15 kDa (Khan and Verma et al., 1990). The production of VIA wassensitive to actinomycin D (Verma and Dwivedi, 1984). The mobile signalproduced VIA in the entire plant system. It appears that the putative messengerbecomes active soon after induction and starts producing VIA, reachesa maximal concentration and then starts to decline.Commonly associated with systemic acquired resistance induced bypathogens is the systemic synthesis of several families of serologically distinctlow molecular weight pathogenesis-related (PR) proteins. The localizationand timing of some PR proteins suggested their possible involvement inacquired resistance against viruses. However, definite proof that the inductionof PR proteins causes the acquired resistance has not been given. Plobnerand Leiser (1990) did not find the production of PR proteins during systemicresistance induced by carnation extract in Xanthi-nc tobacco plants. Absenceof PR proteins during induction of SAR by botanicals suggests that anotherbiochemical chain of reaction, other than one operating in pathogen / chemicalinduced SAR, might be operating during botanical induced systemicresistance against virus infection in plants.Durrant et al. (2004) reported that SAR is a mechanism of induced defencethat confers long-lasting protection against a broad spectrum of microorganisms.SAR requires the signal molecule salicylic acid (SA) and is associatedwith accumulation of PR proteins, which are thought to contribute toresistance.Hansen (1989), while reviewing antiviral chemicals for plant diseasecontrol, gave the following characteristics of an ideal antiviral compoundthat will serve all purposes for virus disease management in crops:●●●●Soluble in water or non-phytotoxic solvents.Effective against at least some agriculturally important viruses atnon-phytotoxic concentrations.Easily taken up by plants and distributed throughout the system.Non-toxic by itself and in its catabolic forms to humans, plants andwildlife.Botanical resistance inducers can be classified as ideal virussuppressingagents, as they have all the characteristics of an ideal antiviralcompound. The resistance-inducing proteins from Boerhaavia diffusa andClerodendrum aculeatum can be applied directly by spraying on systemichosts, for management of some commonly occurring virus diseases undergreenhouse conditions or field conditions. The agricultural role of endogenousantiviral substances of plant origin has been reviewed by Vermaet al. (1995).