SUGARCANE ROOT SYSTEMS: DEVELOPING A TOOLKIT OF METHODS TO UNDERSTAND WHAT'S GOING ON BELOW GROUND

ROOT SYSTEMS ARE essential for crop productivity due to their role in nutrient and water uptake, stool anchorage, ratoon vigour and interaction with soil microbes. Unfortunately the opaque and solid nature of the soil has always been a major limitation for the study of root systems and this is complicated in sugarcane by the size of the plant and the length of the growing season. We have developed a toolkit of reliable methods that enable analysis of large numbers of root samples necessary to overcome the variability due to root system plasticity. Features of the whole root system, including root system opening angle and length of the projected structure, define different soil exploration strategies. Root structural features such as total length, surface area, and size classes can be used to discriminate between varieties and treatments. At the microscopic level, root anatomy contributes functional information. These methods have been applied to root systems from pot and field- grown plants to demonstrate their utility for sugarcane and to reveal new information. Key findings include a strong relationship overall between above-ground biomass and root system size across a large set of genotypes. Results highlighted the importance of fine roots, with 61% of the root system measuring < 0.25 mm in diameter. No changes in the root structure, including the proportion of fine roots, were detected in YCS-affected plants. The methods described here for analysis of root systems will find broad application in the sugar industry, including variety selection and as a diagnostic assay for field root health.