effects of aqueous extracts and total protein content from different plant species on the inhibition of tobacco mosaic virus infection

This study examined the inhibitory properties of aqueous extract and total protein of four plant species: carnation (dianthus caryophyllus), indian privet (clerodendrum inerme), prickly pear cactus (opuntia stricta), and periwinkle (catharanthus roseus) against tobacco mosaic virus (tmv). the aqueous extract and total protein from carnation, indian privet, and cactus significantly reduced tmv infection in the local lesion host, nicotiana glutinosa. conversely, the periwinkle extract did not demonstrate a significant inhibitory effect on tmv. results showed that the inhibitory effects of carnation and indian privet were more effective than those of the cactus extract. the inhibitory effects of the plant extracts applied on the n. glutinosa leaves diminished after washing with water. bioassay tests using total protein from carnation, indian privet, and cactus indicated that the inhibitory effects of these proteins were comparable to those of their respective aqueous extracts. thus, it can be inferred that the inhibitory agents present in these plants are proteins. the findings from both the aqueous extracts and the proteins extracted from carnation, indian privet, and cactus suggest that the inhibitory effects of these substances are localized and not systemic, being confined to the leaves that were treated either simultaneously or prior to the virus inoculation. when n. tabacum (var. turkish), a systemic host, was inoculated with tmv mixed with these plant extracts, there was no evidence of inhibition or a reduction in the incubation period. therefore, using these extracts to manage tmv infections in its main systemic hosts may be ineffective.