Stable chromosome number in horticultural cultivars of Farfugium japonicum (Asteraceae), with descriptions of their morphological characteristics

Abstract

A total of 111 horticultural cultivars of Farfugium japonicum were studied cytologically and described morphologically for the first time. All 111 cultivars with various unusual morphologies, such as dwarf, rumpled leaves, etc., had 2n=60 chromosomes, which was the same number as in wild plants. Only one individual obtained by tissue culture of the cultivar ‘Yukibeni-botan’ had exceptional chromosome number with 2n=59. In 14 cultivars with 2n=60 chromosomes examined, no abnormal chromosome behavior was observed through the microsporogenesis, and at the meiotic metaphase I, 30 bivalents were observed. Among the flowered 96 individuals in 95 cultivars, seven individuals had no pollen grains, and those having atrophied head, such as “SHISHI” and “KURUMA”, showed relatively low pollen stainabilities, 48.3 and 23.4% in average, respectively, whereas the other cultivars had high stainability (91.3% in average). The 2n=59 somaclonal variant of the cultivar ‘Yukibeni-botan’ showed the lowest stainability (0.3%). These results indicate that horticultural cultivars of F. japonicum are stable diploids from the cytogenetical viewpoint, and that the morphological diversity in the cultivars should not be ascribed to the numerical changes of chromosomes but must have been caused by mutation of gene(s) responsible for morphogenesis.