Cryopreservation of somatic embryos of the herbaceous peony (Paeonia lactiflora Pall.) by air drying

This study was carried out to establish a suitable method for the cryopreservation of somatic embryos of the herbaceous peony. The somatic embryos were obtained from cotyledon and anther cultures on a MS medium supplemented with abscisic acid (ABA) and phenylacetic acid (PAA), respectively. The frequency of somatic embryo formation was the greatest (61%) from the cotyledons cultured on a MS medium supplemented with 1.0 mg l(-1) of ABA. Embryos were also obtained directly from anthers cultured on a MS medium with or without 2.0 mg l(-1) of PAA. For the cryopreservation of peony somatic embryos, the embryos were dried under a stream of sterile air and frozen by immersion in liquid nitrogen. Thawed embryos were germinated into plantlets after placing on a medium containing 0.3 mg l(-1) of gibberellic acid (GA(3)). The frequency of the post-thaw regrowth of cryopreserved somatic embryos was related to their size and desiccation time, the latter ranging from 0 to 2 h. When the somatic embryos were desiccated for 1 h, the frequency of post-thaw regrowth was greater than 66%. The frequency of post-thaw regrowth of the cryopreserved somatic embryos from anthers and cotyledon tissues was generally high when they were 2-3 mm in size. Desiccation may be a suitable method for the cryopreservation of somatic embryos of the herbaceous peony.