The micropropagation of chrysanthemums via axillary shoot proliferation and highly efficient plant regeneration by somatic embryogenesis
Protocols for axillary shoot proliferation and somatic embryogenesis were developed for Dendranthema × grandiflora (Ramat.) Kitamura cv. Palisade White. Shoot tips were cultured on a modified Murashige and Skoog (MS) media supplemented with benzyl aminopurine (BA) and gibberellic acid (GA3) or BA, kinetin (Kin) and indole-3-acetic acid (IAA). The auxins indole -3-butyric acid (IBA) and IAA were used to induce rooting. Direct somatic embryogenesis was induced from leaf, internode’s stem and for the first time for chrysanthemums from petiole explants. Modified MS medium supplemented with 1 mg/L naphthalene acetic acid (NAA) or 2,4- dichlorophenoxyacetic acid (2,4-D), 0.1 mg/L BA, 200 mg/L casein hydrosylate (CH) and 290 mg/L proline was used for induction. Proliferation rate of 3.2 new microshoots per one inoculated was achieved when BA (0.1 mg/L) was used in combination with GA3 (0.5 mg/L). The number of roots per shoot was higher using IBA (0.5 mg/L), but IAA (2 mg/L) promoted longer roots. A high percentage of embryogenesis was induced by both combinations of plant growth regulators (PGRs). Leaf explants were most responsive, demonstrating the highest percentage of embryogenesis (97.9%), followed by petiole and internode’s stem explants (56.3 and 35.1%, respectively). The number of somatic embryos per embryogenic explant was also the highest on leaf explants; however, the best conversion rate (53.8%) of somatic embryos to plantlets was observed from petiole explants. For this reason, petiole explants are the most suitable type of explants for plant regeneration of chrysanthemum cv. Palisade White through somatic embryogenesis.
Key words: Chrysanthemum, Dendranthema × grandiflora (Ramat.) Kitamura cv. Palisade White, micropropagation, direct somatic embryogenesis, explant type.