Comparing RSD screening methods for sugarcane and the real costs of diagnosis

Ratoon stunting disease (RSD) is caused by the bacterium Leifsonia xyli subsp. xyli. The disease causes significant yield losses in sugarcane crops (Saccharum hybrids) throughout the world. Three diagnostic techniques for detecting RSD in fields in the Herbert sugarcane region were assessed in 2022: qPCR on leaf sheath biopsy samples (LSB-qPCR); qPCR on expressed xylem sap; and phase-contrast microscopy (PCM) on expressed xylem sap. The LSB-qPCR leaf sheath biopsy is taken from the lowest green leaf sheath of the plant. Differences among techniques were compared for confirmation of the presence or lack of RSD detected, the time required to collect and process samples, the fee to undertake the sampling, safety considerations and transport costs. Differences were identified among the three sampling methods concerning RSD detection, costs associated with sample collection, processing, and some safety related issues. LSB-qPCR was the most efficient and cost-effective diagnostic platform for RSD.