IN VITRO REGENERATION OF THREE CHRYSANTHEMUM (Dendrathema grandiflora) VARIETIES VIA ORGANOGENESIS AND SOMATIC EMBRYOGENESIS

Chrysanthemum (Dendrathema grandiflora) has a high demand in the Colombian and international cut flower markets. Since commercial production of this ornamental species is strongly affected by fungal diseases such as chrysanthemum white rust (Puccinia horiana), high doses of fungicides are being used posing increased environmental and commercial costs. Assessment of in vitro regeneration systems from leaf discs was a first step in developing a plant genetic transformation protocol to obtain fungi-resistant plants. Leaf discs of White Albatross, Yellow Albatross, and Escapade varieties were established in vitro on MS medium supplemented with NAA (0- 4.83 µM) and BAP (0- 13.32 µM) alone and in combination. Leaf discs were also cultured on MumB medium containing 2,4-D (0- 4.52 µM) for 7, 14, and 21 days prior to their transferral to a 2,4-D free MumB medium. Regenerated shoots were individualized, rooted, and hardened. Results show that MS with 4.83 µM NAA + 4.44 µM BAP and 4.83 µM NAA + 13.32 µM BAP induce organogenesis, and MumB with 2.26 µM 2,4-D induces somatic embryogenesis on all three varieties, with exposition periods to 2,4-D of 14 days for White Albatross and 21 days for Yellow Albatross and Escapade. Shoot development from somatic embryos was observed in the three varieties when cultured on a 2,4-D free MumB medium. Spontaneous rooting was recorded in 85 % of the shoots thus facilitating hardening and successful transfer to soil. Key words: Dendrathema grandiflora, in vitro regeneration, organogenesis, somatic embryogenesis