Effects of crossing and selection for seven generations based on flower vase life in carnations (Dianthus caryophyllus L.), and the relationship between ethylene production and flower vase life in the breeding lines

Flower vase life of cut ornamental flowers, including carnations, is important in determining their quality and consumer preference for cut flowers. Therefore, we repeatedly crossed and selected promising offspring with long vase life for seven generations, from 1992 to 2008, in order to improve the vase life of carnation (Dianthus caryophyllus L.) flowers using conventional cross-breeding techniques. We investigated flower vase life, ethylene production at natural senescence, ethylene production after ethylene treatment (autocatalytic ethylene biosynthesis), response time to ethylene treatment (ethylene sensitivity), and flower diameter in six carnation cultivars used for initial breeding materials and a total of 123 selected lines from the first to seventh generations. Our results indicate that there was a large genetic variability in the five traits. Significant negative correlations were observed between flower vase life and ethylene production at natural senescence (r = -0.88**), between flower vase life and ethylene production after ethylene treatment (r = -0.90**), and between flower vase life and flower diameter (r = -0.92**). However, there was no correlation between flower vase life and ethylene sensitivity. Thus, the long vase life of selected carnation lines was strongly associated with a decrease in their ethylene production. Our results indicate that variation in flower vase life is not due to differences in ethylene sensitivity, but due to differences in ethylene production. Although flower size is an important floricultural trait for commercial production, crossing and selection for flower vase life resulted in a considerable reduction in flower diameter. The course of mean flower vase life over generations showed that selection was effectively made in the first to sixth generations. Repeatability for the flower vase life was roughly constant (0.3 to 0.4) in the first to sixth generations, but decreased to 0.12 in the seventh generation, suggesting a decrease in genetic variation in the seventh generation.