Capturing Sugarcane Root System Complexity and Diversity for an Improved Productivity

Sugarcane is a tall perennial grass which is propagated vegetatively from nodal buds and harvested and allowed to regrow over multiple years. The size of the plant as well as the length of the cropping season create challenges for experiments in controlled environments. Consequently root growth remained poorly understood, including the extent of variation between genotypes, the response to environmental constraints, the functional role and turnover of the different root types during the crop cycle, and particularly between seasons.

We developed an analysis framework to study sugarcane root systems at different levels, from root anatomy for traits related to carbon economy, to root morphological traits and root system architecture. Using plants grown in a controlled environment, we first used these methods to screen for sugarcane root system diversity in a collection of Australian varieties and then applied them to study the impact of reduced tillering and nitrogen limitation on root systems. From these studies we identified diversity in root traits that can be selected to obtain varieties better adapted to highly compacted soil, a major issue in sugarcane cultivation.

In order to translate our research findings into field research, we then developed a fast, specific and efficient method for the quantification of live sugarcane root mass in soil samples. This tool was calibrated using a range of Australian and international sugarcane varieties. As a proof of concept, this method was used to investigate the fate of the root system after harvest prior to regrowth of the ratoon crop. There we demonstrated that, two weeks after harvest, the roots from the previous crop were still viable. This raises the question of the role that the former root system plays in the performance of the following crop in this perennial, and demonstrates how this test can be used to provide new insights.