Effects of Cultivar Type and Node Position on Cadmium Accumulation Characteristics of Ratoon Rice

The ratoon rice planting area is gradually expanding, and decreasing Cadmium (Cd) accumulation in ratoon rice is important for food safety and human health. In this study, conventional indica rice (HHZ, Huanghuazhan), three-line indica–japonica hybrid rice (YY-4149, Yongyou 4149), and two-line indica hybrid rice (LY-121, Liangyou 121) were compared regarding ratoon rice yield and Cd uptake, transport, and accumulation. The distribution of Cd at different nodes in the ratoon crop was also examined. The rank-order of the Cd contents in each part (root, stem, leaf, stubble, and spike) of the main and ratoon crops of the tested cultivars was HHZ > LY-121 > YY-4149. The rank-order of the Cd content in each plant part at different nodes in the ratoon crop was HHZ > LY-121 > YY-4149. The Cd content in each plant part increased as the node position (i.e., according to the germination position of regenerated seedlings, the nodes are divided into the second, third, and fourth or fifth node from the top in stubble) was lowered. The redundancy analysis indicated that the low-node brown rice Cd content had the largest effect on the total brown rice Cd content in the ratoon crop. Accordingly, indica–japonica hybrid cultivars should be selected for the production of ratoon rice in mildly Cd-polluted areas, and the height of the main crop stubble should be maximized during harvest.