Plant Cell, Tissue and Organ Culture 21(2): 147-152 (May 1990)
Organogenesis and plant regeneration from immature embryos of Rosa hybrida L.
D. W. Burger, L. Liu, K. W. Zary, C. I. Lee

Abstract

Intact, flowering, rose plants have been regenerated in vitro from excised embryos of crosses between ‘Bridal Pink’ (the maternal parent) and several pollen parents. Explanted embryonic tissues developed into an organogenic callus which formed adventitious shoots after several months only on a modified half-strength Murashige & Skoog medium containing 1.0 µM BA and 0.05 µM NAA. These shoots could be separated, grown individually, rooted in a medium with no BA or NAA, with 1.0 µM IBA, and transplanted to greenhouse media. Embryos ranging in age from 21 to 35 days post-pollination formed organogenic callus that eventually regenerated adventitious shoots. Histological examination of normally-developing embryos showed that well-defined embryonic axes were beginning to develop at approximately 20–25 days postpollination. Analysis of populations of regenerated plants from different crosses showed differences in flower color, growth habit, peduncle length, and petal number. This system may be useful for irradiation-mutation breeding and/or for the development of transgenic rose plants using Agrobacterium tumefaciens.

Abbreviations: BA — 6-benzyladenine; IAA — 3-indoleacetic acid; IBA — 3-indolebutanoic acid; MS — Murashige& Skoog; NAA — α-naphthaleneacetic acid; 2iP-N6-(2-isopentenyl)adenosine

Results and discussion

Immature embryos of rose turned dark-brown within one week of explanting onto culture media. They appeared to be necrotic until cotyledons began to expand after approximately 4-6 weeks. Complete embryo germination was never observed. The cotyledons expanded and developed into a callus mass that was subcultured onto fresh culture medium and adventitious shoots began to form after 5-6 months. Several adventitions shoots were obtained from one original embryo. All four crosses responded similarly to the culture media. Embryos explanted onto solid media and cultured in the light developed organogenic callus. Rose embryos did not respond well to agitated liquid culture or to culture in the dark. The culture protocol developed to induce adventitious shoot formation included a half-strength, solidified, MS medium containing 1.0 M BA and 0.05 M NAA and all culturing was performed in the light.