Morphological and rDNA fluorescence in situ hybridization analyses of chrysanthemum cultivars from Korea

Chrysanthemum is a globally important crop associated with a variety of ornamental products including cut flowers, potted plants, and garden varieties, and high demand for such products has facilitated the development of higher-performing varieties that better meet customer and market requirements. However, chrysanthemum breeding is challenging owing to its complex genetic background and limited knowledge of its genetics and ploidy. To provide more information for breeding material identification in chrysanthemum, we performed both morphological and cytogenetic analysis of 11 chrysanthemum cultivars from Korea. Morphological evaluation of the 11 cultivars revealed that cultivar ‘Green Diamond’ had the tallest plants, ‘Orange Pangpang’ produced the longest cauline leaves, ‘Woonbaek’ had the broadest inflorescences, and ‘Snow Pop’ produced the highest number of ligulate flowers. Cytogenetic investigation suggested that seven of the cultivars (63.6%) were hexaploid (2n = 6× = 54), and the remaining four cultivars (36.4%) were hexaploid-based aneuploids. The cultivars also differed in total chromosome length and in the number 18S rDNA signals, which were located at terminal sites of the short arms. However, all 11 cultivars possessed three pairs of 5S rDNA loci, and those signals were located at interstitial locations of the long arms. These findings will be useful for breeding stock selection, cultivar identification, global communication of new cultivars, and germplasm enhancement.