Fast and efficient root phenotyping of wheat cybrids using an optimized root-pulling force protocol under Tottori sandy field conditions

Improving root system architecture (RSA) requires rapid and practical field-based phenotyping methods. We established a simple vertical root-pulling force (RPF) protocol for characterizing wheat cybrids under the Tottori sandy field conditions. RPF ranged from 1.47–20.61 kg in mature plants and 0.58–6.79 kg in immature plants. The optimized protocol enabled measurements at approximately 5 s per plant and over 1000 plants within 24 working hours for four concurrent operators, while allowing recovery of most of the visible root system with little visible breakage. The cybrids showed substantial variation in RSA-related traits. RPF was most reliable at maturity, with repeatability of 0.83 and significant associations with root area, root biomass, and root-adhering soil mass. In immature plants, RPF repeatability was lower (0.13) and the line effect was not significant ( p = 0.052). The optimized RPF protocol provides a rapid initial screening approach for mature wheat under the uniform sandy field conditions evaluated. RPF does not directly measure complete root system architecture, and root breakage or incomplete recovery cannot be excluded. Projected 2D root area and other measurements of extracted roots should therefore be interpreted as characteristics of the recovered root fraction. Selected lines can subsequently be examined using more detailed root-phenotyping methods when additional architectural information is required.