SugarPATH: a handheld device for advancing sugarcane disease diagnostics

Broadacre cropping is plagued by a multitude of pathogenic organisms that require vigilant surveillance and monitoring to inform management practices and reduce the severity of impact on productivity and yield. Despite the tremendous efforts in developing elaborate systems towards on-farm biosecurity and best management practice, plant pathogens still cause significant yield reductions in the Australian sugarcane industry, partly due to the lack of early, rapid and low-cost pathogen detection methods. Sugarcane pathogens that remain latent for a long period of time or diseases that lack apparent symptoms are particularly problematic. Early and rapid pathogen diagnosis, together with an understanding of disease severity, is critical for the prevention of disease spread as well as for devising an effective management strategy. While bench-based tests for diagnosis of these diseases are routinely performed in centralised laboratories, on-farm diagnostic tools are lacking. Most critically, current laboratory tests usually take weeks to provide results to growers. No rapid test is available for early detection of major sugarcane diseases such as leaf scald and ratoon stunting disease in potentially infected crops. Thus, there remains a need for simple to use, low cost, fast, accurate and specific diagnostics methods. We have developed a novel handheld device: SugarPATH, for the detection of two major sugarcane diseases, leaf scald disease and ratoon stunting disease (RSD). The device comprises an Arduino microcontroller to govern its two central working units: (i) sample processing, and (ii) detection. The sample processing unit contains a microcentrifuge tube-like homemade microreactor for extracting DNA from sugarcane xylem sap extracts. The detection unit employs an RGB sensor for in-situ target (i.e., DNA) detection. The device can detect Leifsonia xyli subsp. xyli (Lxx) and Xanthomonas albilineans (X. albilineans) in samples collected from RSD and leaf scald disease screening trials, respectively. The SugarPATH device is semi-automated, simple to use, low-cost and provides rapid analysis. It takes only 20 minutes to complete a test and can be used in-field for DNA-based diagnosis of sugarcane diseases without needing specialist pathologists. The potential for application of the SugarPATH device across the sugarcane growing sector is obvious.