Genome Size and Chromosome Number Variation Among Caladium Species and Somaclonal Variants

Cultivated caladium (Caladium ×hortulanum) is an ornamental aroid; its genetic improvement has been primarily through hybridization of existing cultivars and breeding lines. Recently there is a strong interest in interspecific hybridization and somaclonal variation for caladium breeding. Our studies have shown that caladium genome sizes vary from 2.98 pg/2C to 9.89 pg/2C and chromosome numbers vary from 2n = 18 to 2n = 38 among species accessions. Genome size and chromosome number data support the species status of C. marmoratum, C. picturatum, and C. steudneriifolium that were previously merged into C. bicolor and the species status of C. clavatum and C. praetermissum. Ten caladium species seem to fall into four cytotype groups based on genome size and chromosome number. Genome sizes and chromosome numbers in Caladium correlate poorly, suggesting that chromosome fusions and DNA losses might have occurred in the evolution of the species that contributed to the development of cultivated caladium. Numerous types of somaclonal variation have been observed in caladium plants regenerated from tissue culture. Chromosome losses or additions seem to be a major cause of caladium somaclonal variations.