A Virus Latent in Carnation and Potato Plants

Abstract

WHILE studying virus diseases of the carnation (Dianthus caryophyllus L.), three different viruses were readily identified by the symptoms they cause in this plant and in sweet william (Dianthus barbatus L.). Attempts to use serology to identify these viruses at first gave conflicting and confusing results, for specific reactions were sometimes obtained with sap from plants known to be infected with unrelated viruses. This became explicable when it was found that some stocks of symptomless carnations contain an antigen that is transmissible to sweet william by inoculation of sap and by the aphid Myzus persicae. Infected sweet william plants show no symptoms, but the multiplication of the antigen in them can readily be identified by serological tests or by electron microscopy. This antigen has also been transmitted to some other species of plants; however, the only one in which it has caused any symptoms, and so justifies calling it a virus, is sugar beet, the older leaves of which sometimes become yellow.