A streak through history: Solving the riddle of chlorotic streak disease of sugarcane

Abstract

AbstractUntil recently, the identity of the pathogen of chlorotic streak disease (CSD) was one of the most enduring mysteries of sugarcane pathology. The mystery continued when the causal agent was revealed as a member of a large group of free‐living eukaryotic microbes that had not previously been associated with any plant diseases. CSD has impacted worldwide sugarcane production since at least the 1920s when it was first noticed simultaneously in Java, Australia and Hawaii. Readily identified by irregular, yellow to creamy‐white chlorotic streaks on the leaves, the identity of the pathogen remained unknown for 90 years. CSD negatively affects germination speed, ratooning, stalk numbers and stalk weight, and later causes stunting of crop growth, leading to major losses in sugar production. Prior to the discovery of the pathogen, CSD was found to be waterborne and spread by infected vegetative propagation material. As such it is particularly damaging in poorly drained soils and areas subject to high rainfall. In severe cases it can lead to crop death. The implementation of successful CSD management strategies has been limited by the lack of knowledge surrounding the nature of this disease. However, these strategies are likely to be augmented with the recent identification of the causal agent, a novel cercozoan described as Phytocercomonas venanatans. This review provides insight into the history, causal agent and potential future developments of CSD management strategies.