Shoot tips of in vitro grown plantlets of Rosa multiflora were cryopreserved using an encapsulation/dehydration procedure. The influence of sucrose and silica gel pretreatments on pre- and post-freeze shoot growth were examined. Shoot tips recovered from liquid nitrogen only grew after 24h pretreatment in medium containing 0.5 M sucrose, followed by 2 h drying with silica gel and rapid freezing.

An investigation was undertaken on the storage characteristics of pollen collected from two English rose cultivars. A rapid decline in viability was observed in pollen stored at +4° C and −20° C, whereas the viability of pollen, stored at ultra-low temperature (−196° C), remained constant. Cryopreserved pollen was shown to retain its ability for fertilisation. The effects of the stage of flower development and anther dehiscence were assessed on both pre-and post-cryopreservation viabilities. Successful long-term storage of pollen will facilitate hybridisation of rose species and cultivars that do not flower synchronously.

The expression of cytoplasmic male sterility (CMS) in Petunia is governed by the nuclear genome and a single plasmagene(S), believed to be located in mitochondria. In the absence of nuclear restorer genes, the S Plasmon causes breakdown of microsporogenesis at meiosis. Fertility is restored if a sufficient number of multiple alleles (mfr) are present; when some alleles are present, the abortion of pollen will occur at different stages (Izhar, 1984).