Morphological trait evaluation of soybean root systems at an early growth stage using image analysis

Root system traits are important for crop production. This study characterized the soybean root system by analyzing position markers and digi- tal images. Soybean genotypes were grown in a growth pouch, and their root systems were photo - graphed every few days using a digital camera. Im - age analysis was performed to segment the roots and measure root length. Three genotypes widely used to provide reference genomes or as major breeding materials were used for Experiment 1. The root dry weight of ‘Williams 82’ at 13 days after transplant (DAT) did not differ significantly with that of ‘Enrei’. However, the root length of ‘Williams 82’ at 8–11 DAT was significantly smaller, whereas that at 13 DAT was comparable with that of ‘Enrei’. Determining the differences by sampling date and root segment revealed that ‘Williams 82’ developed its root system evenly from the middle and bottom segments at 8 DAT, whereas those of ‘Enrei’ and ‘Peking’ developed unevenly from only the bottom segment. Because the genotypes for Experiment 1 had different seed sizes and extent of root elonga - tion, the genotypes with similar seed sizes were used for Experiment 2. Compared with ‘U 1042-1’, ‘COL/PAK/1989/IBPGR/2326(1)’ showed more elongation in the middle root segment at 8–11 DAT. Image analysis enabled a more in-depth investiga - tion of root system development over time and by root segment.