Polyploidization reduces the probability of selecting progenies with high root pithiness and yield potential in radish (Raphanus sativus L.)

Polyploidization affects various plant organs and is widely used in plant breeding programs. This study was conducted to develop a simple and efficient method to generate tetraploid F₂ populations and to investigate the polyploidy effect on the root quality and yield in radish (Raphanus sativus L.) by comparing diploid and tetraploid F₂ populations. Seeds of a F₁ cultivar were immersed in colchicine solution of 0.05, 0.10, 0.50, 1.00 and 2.00% to select the most efficient concentration. Treatment durations were tested for the concentration by immersing seeds for 1, 3, 6 and 12 hours. The ploidy level of colchicine-treated plants was determined using stomata size, flow cytometry and chromosome counts. The diploid and induced tetraploid F₁ plants were self-fertilized to produce F₂ seeds and both diploid and tetraploid F₂ populations were grown in field condition. Immersing radish seeds in 1.00% colchicine solution for an hour was the most efficient in producing tetraploid plants. The leaf weight and number, and root weight and width, on average, were significantly lower in tetraploid than diploid F₂ population. However, root pithiness was significantly lower in tetraploid than diploid F₂ population and most of tetraploid plants had the lowest pithiness scale with some outliers. These results suggest that tetraploid populations from colchicine-treated F₁ cultivars can be useful materials for radish breeding programs by significantly reducing the chances for selecting lines with high root pithiness.