Red-fleshed radishes (RFRs) are economically important root vegetable in the Brassicaceae family that contain high concentrations of radish-red pigment in their fleshy root. However, the yield of the fleshy root is limited and germplasm resources for radish improvement are lacking. Genome doubling is an effective and efficient breeding tool for the rapid creation of new germplasm resources. Therefore, we aimed to induce tetraploidy in RFRs to improve pigment production. RFR seeds were immersed in aqueous colchicine (0, 0.01, 0.05, 0.10, 0.15, and 0.20% (w/v)) for 24 h followed by cultivation at 25℃ for 7 days, and those with uniform and distinctly swelled and short hypocotyls were selected as putative tetraploids. The putative tetraploids were identified by flow cytometry, and then we further examined the morphological and cytological characteristics of the diploid and tetraploid plants and measured gene expression via reverse transcription quantitative PCR. The results indicated that the most suitable concentration of colchicine (0.05% (w/v)) could induce tetraploidy in RFRs, with a tetraploid-induction rate as high as 34.50%. In addition, tetraploids exhibited a “gigantism” effect in both morphological and cytological traits, including swelled hypocotyls, thicker cotyledons, larger stoma, wider and longer leaves, taller plants, larger flowers, increased pollen size, larger seed pods and seeds, and a larger taproot. Moreover, compared with diploid plants, the pigment content and yield of pigment per plant of tetraploid plants were increased by 65.11% and 216.82%, respectively. Therefore, we present a simple and efficient method for tetraploid induction via soaking radish seeds in 0.05% (w/v) colchicine for 24 h. The results showed that tetraploid plants not only exhibited obvious “gigantism” effects but also significantly enhanced accumulation of anthocyanins, and represent a practical breeding material for improving pigment yield in RFRs.

红肉萝卜 (RFR) 是十字花科中经济上重要的根茎类蔬菜，其肉质根中含有高浓度的萝卜红色素。但肉质根产量有限，缺乏萝卜改良种质资源。基因组加倍是快速创造新种质资源的有效且高效的育种工具。因此，我们的目标是在 RFR 中诱导四倍体，以提高色素产量。将 RFR 种子浸入秋水仙碱（0、0.01、0.05、0.10、0.15 和 0.20% (w/v)）水溶液中 24 h，然后在 25℃下培养 7 天，那些具有均匀、明显肿胀和短下胚轴的种子被选为推定的四倍体。通过流式细胞术鉴定推定的四倍体，然后我们进一步检查了二倍体和四倍体植物的形态学和细胞学特征，并通过逆转录定量 PCR 测量了基因表达。结果表明，秋水仙碱最适宜浓度(0.05% (w/v))可诱导RFRs四倍体，四倍体诱导率高达34.50%。此外，四倍体在形态学和细胞学特征上都表现出“巨人症”效应，包括下胚轴肿胀、子叶更厚、气孔更大、叶子更宽更长、植株更高、花朵更大、花粉更大、种子荚和种子更大，以及更大的主根。此外，与二倍体植物相比，四倍体植物的色素含量和单株色素产量分别增加了65.11%和216.82%。所以，我们提出了一种简单有效的四倍体诱导方法，通过将萝卜种子浸泡在 0.05% (w/v) 秋水仙碱中 24 小时。结果表明，四倍体植物不仅表现出明显的“巨人化”效应，而且显着增强了花青素的积累，是提高RFRs色素产量的实用育种材料。