The nature of the causal agent of white leaf disease of sugarcane

Abstract

The general failure of grafting techniques with sugarcane, as with other monocotyledons, has prevented their use to test for the transmissibility of the agent responsible for white leaf disease. Sugarcane with white leaf can be cured by heat treatment, and a technique was developed to exploit this finding in a manner which demonstrated the movement of the causal agent from diseased to healthy tissue and thus accomplished an objective for which graftage is used in many other plant virus investigations. The technique also provided evidence for the replication of the causal agent. The length of the incubation period following heat treatment varied directly as the severity of the treatment and suggests that those plants showing symptoms after a long incubation period could be explained by assuming that the disease principle undergoes a quantitative change until finally it becomes sufficiently concentrated to cause the white leaf symptoms. This increase in the amount of the disease principle is believed to be the result of multiplication. In the absence of any detectable pathogenic microscopic organism in or on the tissues of any part of the affected stalk at various stages, the evidence indicates that the causal agent of white leaf disease of sugarcane is a virus.