Genome Size and Chromosome Number Variation among Caladium Species

The genus Caladium is a member of the aroid family, consisting of seven to 17 species that are indigenous to the tropical South and Central America. Cultivated caladium (C. ×hortulanum) has been a major floricultural crop in the United States, especially in the southern and southeastern states. Genetic improvement of cultivated caladium has been primarily through hybridization among existing cultivars. To broaden the genetic base of cultivated caladium and/or to introduce biotic, abiotic stress tolerance traits may necessitate more interspecific hybridizations. Our studies have shown that caladium genome size ranges from 2C = 2.98 pg in C. lindenii to 2C = 9.89 pg in C. ×hortulanum cv. Chang Suek. All cultivated caladium varieties as well C. bicolor and C. schomburgkii have 2n = 2x = 30 chromosomes. The somatic chromosome number of other six caladium species varies from 2n = 2x = 20, 24, and 26 to 2n = 2x = 34 and 38.  This unusual wide-range chromosome number variation seems to be the main contributing factor of the genome size variation among caladium species. These results provide new insights into the relationships among caladium species and shed light on the origin of cultivated caladiums. The available information will be valuable for guiding future interspecific hybridization in caladium.