Innovative approaches to identifying the cause of chlorotic streak and new management strategies: final report 2013/357

Abstract

Chlorotic streak is one of the major diseases in the Australian sugar industry. The disease occurs in areas of high rainfall and poorly drained fields and is a limitation to productivity, particularly during seasons that are wetter than average. The cause of the disease was unknown for 87 years before being identified through a combination of modern molecular techniques, particularly Next Generation Sequencing, and traditional pathology and microscopy. The causal agent is a novel biflagellated cercozoan and Phytocercomonas venanatans has been assigned as the tentative name. It is the first plant pathogenic cercozoan able to systemically infect higher plants and also the first to be successfully grown in axenic culture on common microbiological media. The ability to culture the organism opens the way to developing innovative methods of control. Until now, there has been no reliable method to screen varieties for resistance to chlorotic streak due to the difficulty of setting up replicated screening trials with controlled infection. The project assessed both field-based and glasshouse-based screening. Using the cultured organism as inoculum was considered the most promising way of delivering a rapid resistance screening method. Other outcomes include improved diagnostic screening methods to assist Productivity Services staff, an understanding of epidemiology and a better understanding of the biology of the causal agent.