Breeding for Long Vase Life in Dahlia (Dahlia variabilis) Cut Flowers

抄録

Flower vase life is one of the most important traits for ornamental plants. The vase life of cut dahlia (Dahlia variabilis) flowers is very short, and genetic improvement of this trait is desirable. We started a breeding research program in 2014 to improve the vase life of dahlia flowers using conventional cross-breeding techniques. We found large significant differences in flower vase life among 24 dahlia cultivars: Nine cultivars had long vase life (e.g., ‘Syukuhai’, ‘Rinka’, and ‘Micchan’); eight had normal vase life (e.g., ‘Kamakura’, ‘Agitate’, and ‘Benifusya’); and seven had short vase life (e.g., ‘Gin-Ei’, ‘Port Light Pair Beauty’, and ‘Yumesuiren’). We used 22 cultivars as initial breeding materials, repeatedly crossed them, and selected promising offspring with long vase life for three generations from 2014 to 2018. Two cycles of selection and crossing led to a 1.7-day increase in vase life (population mean) from the first to the third generation, clearly showing that this approach can extend the vase life of dahlia flowers. The mean vase life of ‘Kamakura’, a leading white dahlia cultivar in Japan, was 5.0–6.2 days in distilled water, 6.0–6.8 days in an isothiazolinic antibacterial agent CMIT/MIT solution (5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one) and 6.0–7.6 days in a GLA solution (10 g·L⁻¹ glucose, 0.5 ml·L⁻¹ CMIT/MIT, and 50 mg·L⁻¹ aluminum sulfate), whereas in six finally selected lines it was 6.2–12.0 days in distilled water, 6.6–10.2 days in CMIT/MIT solution, and 9.4–13.6 days in GLA solution (1.4–2.1 times that in ‘Kamakura’). In particular, the selected second-generation line 606-46 showed a stably longer vase life than ‘Kamakura’. ‘Micchan’, which has a long vase life, was a common progenitor used for breeding of parental lines in cross combinations with long vase life in the second generation and all cross combinations in the third generation. The final six selected lines with long vase life were all progeny of ‘Micchan’. Our results strongly suggest that ‘Micchan’ has genes related to long flower vase life, and that the trait is heritable.