Abstract
Phenotypic variation and correlations among root traits form the basis for selecting and breeding soybean varieties with efficient access to water and nutrients and better adaptation to abiotic stresses. Therefore, it is important to develop a simple and consistent system to study root traits in soybean. In this study, we adopted the semi-hydroponic system to investigate the variability in root morphological traits of 171 soybean genotypes popularized in the Yangtze and Huaihe River regions, eastern China. Highly diverse phenotypes were observed: shoot height (18.7–86.7 cm per plant with a median of 52.3 cm); total root length (208–1663 cm per plant with a median of 885 cm); and root mass (dry weight) (19.4–251 mg per plant with a median of 124 mg). Both total root length and root mass exhibited significant positive correlation with shoot mass (p ≤ 0.05), indicating their relationship with plant growth and adaptation strategies. The nine selected traits contributed to one of the two principal components (eigenvalues > 1), accounting for 78.9% of the total genotypic variation. Agglomerative hierarchical clustering analysis separated the 171 genotypes into five major groups based on these root traits. Three selected genotypes with contrasting root systems were validated in soil-filled rhizoboxes (1.5 m deep) until maturity. Consistent ranking of the genotypes in some important root traits at various growth stages between the two experiments indicates the reliability of the semi-hydroponic system in phenotyping root trait variability at the early growth stage in soybean germplasms.
Highlights
The nine root traits reflected the pattern of root distribution and development
Group 5 contained three genotypes with a large root system. These results demonstrate that genotypes from the same root size were not always clustered into the same or closer group(s)
Soybean selection and breeding programs mainly focus on aboveground traits and yield, with the impact on root traits often ignored [27,41]
Summary
Merr.) is an important leguminous crop that is used for human food, animal feed, biofuel production, and many other products due to its high protein and edible oil content [1]. Soybean is native to China and is the fourth largest crop after rice (Oryza sativa L.), wheat (Triticum aestivum L.), and corn (Zea mays L.) of the world. It is grown on an estimated 6% of the world’s arable land [1,2]. In China, the region between the Yangtze and Huaihe Rivers is among the major soybean-producing area [2]
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