Sugarcane root systems for increased productivity; development and application of a root health assay : final report 2015/002

Abstract

A better understanding of the sugarcane root system has the potential to improve productivity and overcome soil constraints. By adapting the digital methods that have been developed in other crops, we have developed a toolkit of reliable methods that enable analysis of large numbers of root samples. These methods have been used to provide a baseline understanding of the range and variation of root parameters for sugarcane, including root/shoot ratios, root opening angle, root length, proportion of fine roots, branching density, average diameter and diameter in each size class. We found a consistently high proportion of fine roots, but there was genetic variation for many other key traits amongst current commercial lines. Importantly, there were no significant reductions in root system size or quality in modern varieties compared to older varieties. The methods and baseline were then applied to test the response to stresses encountered in Australian growing environments. When comparing plants with or without YCS symptoms, we found no differences in root system structure, despite significant reductions in shoot mass. Limiting growth by removal of tillers or by restricting nitrogen availability identified plasticity in specific root traits that enabled the plants to adapt to the restrictions. Root system distribution by depth, and relative allocation of resources to the root system showed adaptations to stress while root angle appeared to be stable. With the new methods and knowledge of trait plasticity, we can now start to test which traits provide a benefit in various agronomic situations and develop an integrated understanding of root health which can be used to monitor soil health and promote the adoption of better agronomic practices.