Abstract:

To screen out the effective method and the optimal scheme for determining pollen viability of Dahlia, as well as to understand the pollen viability of Dahlia cultivars, four methods were used to detect the pollen viability of Dahlia cultivars. On this basis, single factor experiment and orthogonal design experiment were adopted to optimize the culture conditions and medium components of Dahlia pollen germination in vitro, and then the pollen viability of different cultivars was further detected and compared. The results show that TTC staining method could not make pollen coloration, I₂-KI staining and sporopollen staining could not effectively distinguish the active and inactive pollen, while in vitro germination culture method is an effective method to determine the pollen viability of Dahlia, which could accurately and intuitively reflect the test results. The pollen germination rate is the highest when the pH is 6.0, the cultivation temperature is 25℃ and the cultivation time is 2.5 h. The effects of medium components on the pollen germination in vitro for Dahlia are as following: PEG> sucrose> boric acid. The best combination is A₃B₄C₂ formulated with 25 g/L PEG 4000, 60 g/L sucrose and 50 mg/L boric acid, and the highest pollen germination rate is up to 62.1%. The pollen viability of 22 Dahlia cultivars is detected using the optimal scheme obtained above, the pollen germination rate is 11.75%-78.72%, and the pollen germination rate of different cultivars varies greatly. The pollen germination rate of ‘Orchid Princess’ is the lowest while that of ‘Pocher’ is the highest. The pollen viability of Dahlia cultivars is rich in diversity. Among the 22 Dahlia cultivars tested in this study, 14 cultivars are fertile and could be used as male parent when crossing, and eight cultivars are semi-sterile or low sterile, which are more suitable for female parent.

Key words: Dahlia, pollen viability, in vitro germination, cultivation condition, medium components