natural-products-in-plant-pest-management

162 H.N. Verma and V.K. BaranwalVerma and Awasthi (1980) reported that the synthesis of VIA is inhibitedif AMD is applied soon after extract treatment. The VIA synthesized is neithervirus specific nor host specific. Extracts containing VIA when incubated withthe virus reduced their infectivity. VIAs from a few hosts have been characterized.The VIA synthesized in the leaves of N. glutinosa, treated with B.diffusa root extract reduced infectivity of TMV on N. glutinosa, Datura stramoniumand D. metel (Verma and Awasthi, 1980). It was, however, less effectivein inhibiting TRSV and GMV on C. amaranticolor. The VIA production wasmaximum after 24 h treatment with the extract. The VIA has a proteinaceousnature (Verma and Awasthi, 1980). VIA synthesized in C. tetragonoloba plantsfollowing treatment with B. spectabilis leaf extract prevented infection oftobamoviruses in seven hypersensitive hosts (Verma and Dwivedi, 1984) andits production was maximum after 48 h treatment. The VIA showed characteristicsof a protein (Verma and Dwivedi, 1984). VIA produced in the samehost upon treatment with Pseuderanthemum bicolor extract completely preventedinfection of SHRV, TMV, CGMMV, and PVX on C. tetragonoloba, D.stramonium, C. amaranticolor and G. globosa, respectively (Khan and Verma,1990).VIA and the antiviral state are induced concomitantly with the systemicresistance induction in host plants, following treatment with certain plantextracts. VIA is an inducible gene product like AVF, IVR and PR proteins. Thephytoproteins occurring in the root / leaf extracts of Boerhaavia diffusa, Clerodendrumaculeatum, Clerodendrum inerme and B. spectabilis etc. possess strongsystemic-resistance-inducing properties (Verma and Prasad, 1992).Clerodendrum aculeatum and Boerhaavia diffusa, the two potentantiviral plantsClerodendrum and Boerhaavia are economically important plants becausemany of their species possess medicinal properties. Almost every part ofthese plants is credited with some medicinal properties and is employed intraditional Indian system of natural therapy.Virus inhibitors from Boerhaavia diffusa and Clerodendrum aculeatuminhibit several plant viruses. These inhibitors modify the susceptibility ofhost plants towards virus infection. The roots of B. diffusa are a rich source ofa basic protein, which has been used for inducing systemic resistance inmany susceptible crops against commonly occurring viruses (Verma andAwasthi, 1979, 1980; Verma et al., 1979; Awasthi et al., 1984, 1985, 1989; Vermaet al., 1995, 1999). This protein or antiviral agent was active against sphericaland tubular viruses in hypersensitive hosts such as Datura metel, Nicotianatabacum var Ky-58, N. glutinosa / TMV, Cyamopsis tetragonoloba / SHRV, Vignasinensis / SHRV, and systemic hosts such as Nicotiana tabacum c.v NP-31 / TMV,Crotolaria juncea / SHRV, N.glutinosa / TRSV, when applied a few hours (17–24h) before virus inoculation or when tested after mixing with virus inoculum(Verma and Awasthi, 1979; Awasthi et al., 1984). The inhibitor is a basic glycoprotein(70–80% protein, 8–13% carbohydrate) with a molecular weight of