Improved efficiency of crop root system analysis

<p>Root system is an important breeding target because it affects water and nutrient uptake. Improving the root system can enhance important traits such as fertilizer absorption efficiency and drought stress tolerance. However, root collection and measurement in soil are laborious and destructive, making root system not to be a priority target for breeding. This mini-review introduces recent research trends focusing on labor-saving root collection and measurement, and development of nondestructive measurement techniques. In root collection, steel monoliths and a backhoe were used to collect rice (Oryza sativa) roots to save labor. A monolithic study of rice cultivars worldwide quantitatively evaluated the differences in tiller numbers, correlated with root biomass, and crown root diameters among rice subpopulations. In root measurement, a deep learning-based image analysis was used to measure rice roots to save labor. The trench method is a technique to dig trenches next to crops to observe the distribution of crop roots in soil. By analyzing trench images with deep learning, distribution diversity of roots in soil of rice varieties worldwide was evaluated. In nondestructive measurement, image analysis software was developed to analyze X-ray CT (computed tomography) images. Optimal cultivation and imaging conditions were determined, and shape of root system was visualized and quantified from the CT images. As described above, the labor-intensive tasks of root system analysis both indoors and outdoors had been improved in efficiency. Using these techniques, breeding related to root systems is expected to be further promoted.</p>