Screening Low-Cadmium and High-Mineral Nutrient Rapeseed (<i>Brassica napus</i> L.) Cultivars According to the Uptake and Transport Characteristics of Elements

Screening the edible parts of low-cadmium (Cd) and high-nutrient crop cultivars is an effective method for reducing Cd intake and enhancing the absorption of beneficial elements for humans. In a hydroponic experiment with Cd toxicity treatment (5 μmol/L CdCl₂), we analyzed the differences in the absorption and transport characteristics of Cd and mineral nutrients in 30 rapeseed (<i>Brassica napus</i> L.) cultivars during the seedling stage, as well as the correlations between various elements. Firstly, Pearson correlation analysis indicated that Cd content in the shoot parts of 30 rapeseed cultivars was not correlated with the Cd uptake ability of the roots and was obviously positively correlated with the Cd translocation coefficient from root to shoot (r = 0.452 *, <i>p</i> < 0.05). Hierarchical clustering selected 26 cultivars with lower Cd content in the shoots, and correlation analysis of Cd and other nutrient element contents in the shoots of the 26 cultivars revealed significant negative correlations (r = −0.40 *, <i>p</i> < 0.05; r = −0.45 *, <i>p</i> < 0.05) between iron (Fe) and magnesium (Mg) content and Cd content, while potassium (K), calcium (Ca), manganese (Mn), and zinc (Zn) content had no correlation with Cd content. Then, hierarchical clustering screened 19 cultivars with higher dry weight, 4 cultivars with higher K content, 1 cultivar with higher Ca content, 8 cultivars with higher Mn content, and 3 cultivars with higher Zn content. Finally, a Venn diagram identified four superior rapeseed cultivars with lower Cd and higher nutrients in the shoots, namely, OJ114 (lower Cd, higher Mn and K content), BN365 (lower Cd, higher Mn, Fe, and Zn content), BN275 (lower Cd, higher Ca, Zn, Mn, and Fe content), and BN112 (lower Cd, higher K, Mg, Fe, and Mn content).