Somaclonal variation in 'Red Flash' caladium: morphological, cytological and molecular characterization

Somaclonal variation is a major concern to many applications of plant cell and tissue culture techniques, yet it could be a useful source of variation for plant genetic improvement. High frequencies of somaclonal variants were reported in caladium, but little was known about changes in caladium somaclonal variants at the cellular and molecular levels. Twenty-four somaclonal variants were identified among 'Red Flash' caladium plants regenerated from two types of leaf explants and on two media containing different auxins. Results showed that the type of leaf explants and auxin affected the occurrence of somaclonal variants in 'Red Flash'. The highest percentage of variants (25.0 %) was observed among plants regenerated from mature leaf explants cultured on the media containing 2,4-dichlorophenoxyacetic acid. These somaclonal variants exhibited considerable changes in leaf shape, coloring of the main veins, spots, margins, and leaf size, and could be separated into 10 somaclonal variant groups. Twelve variants contained 1.1-5.4 % less nuclear DNA and appeared to have lost one chromosome. Two variants contained 5.4-9.2 % less nuclear DNA and appeared to have lost two chromosomes. One variant contained 95.0 % more nuclear DNA and 2n = 58 chromosomes. Two SSR markers (CaM1 and CaM103) revealed DNA banding pattern changes in nine variants, including allele loss in eight variants and allele size change in one variant. These results suggested that several cytological and/or molecular causes were involved in the somaclonal variation in 'Red Flash' and chromosome number change was a frequent cause leading to a high frequency of aneuploids and marker allele loss. The CaM1-carrying chromosome seemed to be unstable and prone to loss during tissue culture.