Somatic Embryogenesis and Somatic Embryo Germination of Camellia Azalea × Camellia Japonica ‘Maiden of Great Promise'

Camellia azalea Wei. is a rare and distinct species of the genus Camellia.  This plant is unique in that it blooms nearly every month of the year.  Although this is a highly desirable trait this species is also native to zone 10 and highly difficult to propagate.  Additionally, when attempting to hybridize with this species, seed rarely forms.  When seeds are produced, they are often under developed and nonviable when sown in vivo.  Underdeveloped seeds were collected from mature fruit from the cross C. azalea × C. japonica ‘Maiden of Great Promise’.  Seeds were cultured on MS media containing 10 mg·L^-1 6-benzylaminopurine (BAP), which triggered the production of primary and secondary somatic embryos.  Secondary somatic embryos were cultured on MS media, with 1 mg·L^-1 indol-3-butyric acid and four treatments consisting of 1 mg·L^-1 BAP, 1 mg·L^-1 BAP plus 1 mg·L^-1 GA₃ (GA), 1 mg·L^-1 GA, and no additional hormones (control).  All cultures were placed in a growth chamber under constant light and a temperature of 23 °C.  Each explant was evaluated for number of secondary somatic embryos formed, number of germinated somatic embryos, and maximum width of the culture.  At 12 weeks, the size of cultures in tubes that contained BAP and GA were significantly larger than cultures with just GA or with no added hormone.  The average number of somatic embryos per tube increased to 5.9 for culture on media that contained only BAP, 4.3 for cultures with BAP plus GA and 3.0 - 3.1 for all other cultures.  Explants treated with BAP plus GA had the highest number and percentage of germinated embryos 4, 8 and 12 weeks after culture and the number of germinated embryos were significantly higher than all other treatments at 12 weeks. Results indicate that neither BAP nor GA is required for secondary somatic embryogenesis or germination of somatic embryos, which occurred with all treatments.  The presence of BAP at 1 mg·L^-1 can increase the rate of explant growth, the number of secondary somatic embryos formed and the number of germinating somatic embryos.  Embryo explants cultured on media with BAP plus GA produced the highest number and percentage of germinated embryos, GA alone did not have a significant effect on somatic embryo production or germination but does seem to have a synergistic or additive effect with BAP.