Inhibitory effects of certain plant extracts on the incidence of cowpea mosaic
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Date
1990
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Department of Plant Pathology, College of Agriculture, Vellayani
Abstract
The inhibitory effect of certain plant extracts on the incidence of cowpea mosaic was studied.
Preliminary screening of non-host plants for antiviral property against cowpea mosaic virus revealed that extracts of sixteen plants viz. Adenocalyma allicea, Azadirachta indica, Boerhaavia diffusa, Bougainvillea spectabilis, Calotropis gigantean, Clerodendron inflortunatum, Curcuma longa, Eupatorium odoratum, Ferrula indica, Mirabilis jalapa, Moringa Olifera, Phyllanthus niruri, Polyalthia longifolia, solanum indicum, Thespesia populnea and Vitex negundo inhibited the production of local lesions on the leaves of Chenopodium amaranticolor indicating that these extracts possessed antiviral property.
The extracts of A. Indica, B. diffusa, B. spectabilis, C. gigantean, C. infortunatum, C. longa, M. jalapa, P. niruri, S. indicum, and V. negundo caused 100 per cent inhibition of the production of local lesions on C. amaranticolor even at five per cent concentration. The inhibitory effect of the plant extracts was found to be less pronounced when tested on the primary leaves of cowpea seedlings.
Pre - inoculation application of plant extracts was found to be more effective than post-inoculation application in checking the incidence of cowpea mosaic. In insect transmission studies with Aphis craccivora cent per cent inhibition of disease incidence was obtained with the extracts of A. indicum, C. infortunatum, P. niruri and V. negundo.
Studies on the effect of plant extracts on the acquisition and transmission of cowpea mosaic virus by A. craccivora revealed that the extract of P. niruri caused 100 per cent reduction over control.
Maximum inhibition of disease development was obtained in plants inoculated with cowpea mosaic virus upto two days after the application of extracts of A. indica, P. niruri, V. negundo and C. infortunatum.
Extracts of V. negundo and A. indica caused considerable reduction in the survival of A. craccivora on cowpea.
The present studies indicated that, the extract of C. infortunatum had some systemic effect against cowpea mosaic virus.
Repeated application of plant extracts on cowpea plants revealed that V. negundo had the maximum inhibitory effect on symptom development, in both sap and insect transmission trials.
Height and weight of plants, number and weight of pods and root nodules of cowpea plants treated with plant extracts were found to be more than that of the control.
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170310