Abstract
In order to breed early flowering and highly productive cultivars with long vase life or disease resistance in the carnation (Dianthus caryophyllus L.), genetic variation and photoperiod responses in earliness of flowering were studied in a phytotron experiment using recent standard-type carnation cultivars, interspecific hybrids between the carnation and D. superbus var. longicalycinus and their backcrossing progenies. Our results indicate that there was a large genetic variability in flowering times and photoperiod responses among the tested 11 materials. In ‘Mizuki’ and ‘Rachel’, which were two of the earliest flowering cultivars in the preliminary test using 21 cultivars, the mean number of days to flowering was less than 100 days for long days (LD) treatment, and all tested plants flowered within the experimental period (a 169-day period) for short days (SD) treatment. However, ‘Hitomi’, ‘Karen Rouge’, and ‘Miracle Rouge’ did not flower in all their tested plants within the experimental period for SD treatment. Our results showed that interspecific hybrids between the carnation and D. superbus var. longicalycinus and their backcrossing progenies are facultative long-day plants, which means that they flower faster with LD than with SD treatment. Although the crosses using ‘Rachel’ as the seed parent produced no seed, the crosses using ‘Mizuki’ as the seed parent showed high-cross compatibility and produced many progenies. The F1 seedlings using ‘Mizuki’ as the seed parent showed a very early flowering habit, compared to the F1 seedlings using ‘Le France’ as the seed parent. These results suggest that earliness of flowering in ‘Mizuki’ is heritable.
