THE INHIBITORY ACTIVITY OF EXTRACT OF CAPSICUM FRUTESCENS ON PLANT VIRUS INFECTIONS

Abstract

The expressed juice from Capsicum frutescens L. contains a substance that markedly decreases the formation of local and primary lesions by certain viruses on cowpea and Chenopodium hybridum L. and to a lesser extent on Nicotiana tabacum vars. Harrow Velvet and Samsun, and Physalis peruviana L. The extent to which pepper juice decreases the numbers of lesions is independent of the virus concerned and depends only on the species to which inoculations are made. Pepper juice inhibits the production of local lesions when it is applied with the virus inoculum, or to the upper and lower leaf surfaces before inoculation; but, if applied to leaf surfaces a few minutes after inoculation, pepper juice does not appreciably decrease production of lesions. Thus, it would seem that the effect of the inhibitive agent is to prevent infection by, rather than increase of, the virus. The application of the pepper extract at some distance from the point of virus inoculation also inhibits lesion formation on cowpea and Chenopodium. As judged by the reduction of lesions on cowpea, pepper extract displays about the same degree of inhibition as that of spinach, this being much greater than that of cucumber. The inhibitive component of pepper juice is thermolabile, it resists aging and drying in vitro, and does not pass through a cellophane membrane. Such characteristics indicate its protein nature. The protein component of pepper juice precipitated either by 95% ethanol or by ammonium sulphate is inhibitively active, but is less so than the raw juice.