Natural occurrence of mixploid ginger (Zingiber officinale Rosc.) in China and its morphological variations

•The basic chromosome of Zingiber officinale was x = 11, at least for the Chinese ginger.•The natural occurrence of a 2x-4x mixploid in ginger was found.•Phenotypic alterations occurred in response to changes in ginger ploidy level.•Single finger mass of Z. officinale was used as a key morphological character to distinguish mixploid from diploid.•A simple and convenient method of screening for mixploid in Z. officinale is available.

Ginger (Zingiber officinale Rosc.) is widely used around the world as an important medicinal crop. The extensive geographic variations in Chinese ginger contribute to the many ecotypes and rich diversity among cultivated ginger. Sixty-three ginger varieties representing diverse geographic locations in China were analyzed for ploidy by flow cytometry. Chromosome numbers were counted in actively growing root tips using conventional rapid squash techniques. Our results indicated that 25.4% of the accessions were mixploid with diploid and tetraploid cells, and 74.6% of the accessions were diploid. No solid tetraploid or other polyploidy occurred in nature. The basic chromosome number of ginger in China is x = 11. The natural occurrence of mixploid in ginger may result in a highly effective method for ginger polyploidy breeding. Phenotypic alterations occurred in response to changes in ginger ploidy level. Mixploid ginger was typed as a ‘giant ginger’ with stronger stems, fatter fingers, and bigger rhizomes, fewer shoots, and the diploid was typed as ‘small ginger’ with thinner stems, more shoots, and a smaller single finger and rhizomes. The single finger mass of ginger was the most important key morphological character distinguishing the mixploid from the diploid. Morphological differences in ginger may represent different ploidy levels rather than differing geographical distribution.