Pollen cryopreservation of Japanese tree peony cultivars

In order to prolong pollen viability, pollen of 23 Japanese tree peony (Paeonia suffruticosa Andr.) cultivars were cryopreserved in liquid nitrogen. In vitro germination of both fresh and cryopreserved pollen was examined by the hanging-drop method. The results showed that the germination rate of fresh pollen varied with cultivars, with the highest value (60.89%) in P. ‘Shimane Chojuraku’ and the smallest (3.49%) in P. ‘Shimadaijin’. At room temperature, pollen viability of most cultivars was lost within 15 days, but cryopreservation prolonged pollen viability for at least two years. After two years, cryopreserved pollen still retained a high germination rate, which was even higher than that of fresh pollen in some cultivars. We conclude that cryopreservation is applicable for long-term preservation of pollen of Japanese tree peony.