In order to develop rich new varieties of peony flowers and solve the problems associated with non-synchronised flowering, a study was conducted to investigate pollen viability of fifteen herbaceous peony cultivars. Pollen was stored for more than one year under four storage conditions (4 °C, -4 °C, -20 °C, and -76 °C). In vitro germination and the I2-KI staining method were used to test pollen viability. For all cultivars, pollen stored at -76 °C showed a significantly slower rate of viability reduction when compared to all the other storage conditions. The differential results obtained using different pollen viability assays confirmed that the in vitro germination test showed lower viability compared to I2-KI staining method. The pollen tube length grew longer as storage temperature rose such as 'Hongfeng'. From the present study, it has been proved that the I2-KI staining method is more convenient and reliable than the in vitro germination test. Herbaceous peony pollen can be stored at 4 °C for hand-pollination among cultivars having non-synchronised flowering in a season, and that different storage temperature is suited to different herbaceous peony pollen for more than one year.
Keywords: Cross pollination; Herbaceous peony; I2-KI staining method; In vitro germination; Pollen viability.