Development of a method for high-throughput quantitation of soil-surface roots of rice (<i>Oryza sativa</i>) and wild rice (<i>O. glumaepatula</i>) using an overhead scanner

Abstract

SOil-surface Roots (SORs) are roots that elongate over or near the soil surface. They allow plants to escape waterlogging-caused hypoxia and high salinity that are often present in deeper soil. Quantitative evaluation is essential for understanding SOR function and identifying the genes and quantitative trait loci (QTLs) that control it. However, existing methods to evaluate SOR formation are laborious/slow or semiquantitative. Here, we describe a high-throughput quantitative SOR evaluation system that uses an overhead scanner. We evaluated SORs in 56 wild rice (Oryza glumaepatula) introgression lines (ILs) with the genetic background of O. sativa. The method can quantify the SOR area of a plant in less than 90 sec. During the image analysis process, multithreshold segmentation on the scanned images reduced the reflection noise of the digital image and improved the accuracy of the estimation of SORs formation. The root surface areas of SORs of the O. glumaepatula ILs varied widely, which should make them well-suited for identifying SOR-related QTLs. The overhead scanner method has the potential to quantitatively and rapidly evaluate SORs developed on the soil surface.