Micropropagation of ornamental pineapple (Ananas comosus var. bracteatus) by plantlets etiolation and regeneration.

The market of tropical flowers is expanding, and the marketing of ornamental pineapple inflorescence is also increasing. Etiolated nodal segments are used for micropropagation of several crops. The aim of this work was to evaluate the use of etiolated nodal segments for micropropagation of ornamental pineapple Ananas comosus var. bracteatus. Stems obtained from in vitro subcultured plantlets were inoculated, in medium MS and stored in darkness at 24±1ºC. Four treatments were used: MS without growth regulators; MS + 10mM of naphtalenacetic acid (NAA); MS + 10mM of indolacetic acid (IAA); MS + 10mM of indolbutiric acid (IBA). At the end of 60 days were evaluated: number of etiolated shoots/stem; number of nodes/etiolated shoot; etiolated shoot length, internode length and total number of nodes/stem. There was no difference in the number of etiolated shoots per explant among the evaluated treatments. The medium MS without growth regulators produced greater number of nodes per etiolated shoot and of total number of nodes per explant, differing statistically from the media with IBA and NAA for the first variable and IAA and NAA for the second one. The lowest values for etiolated shoot length and for internode distance were obtained at the medium with NAA, and the other treatments did not differ significantly among themselves. Nodal segments having two nodes obtained from in vitro etiolated stems were placed for 60 days in medium MS without growth regulators to plantlet regeneration. The treatments were: MS without growth regulators; MS + 4,44 mM of 6-benzylaminopurine (BA); MS + 8,88 mM of BA; MS + 13,32 mM of BA. The flasks were incubated under photoperiod of 16 hours, at 24±1ºC. At the end of 30, 45, 60, days were evaluated the number of regenerated plantlets per node. At 30 days, there was no difference in the number of regenerated plantlets/node among the tested treatments. At 45 days, 13,32 mM of BA did promote the highest number of regenerated plantlets, which differed from the medium MS without the addition of this cytokinin. At the 60 days, this same medium did promoted the highest number of plantlets per node, differing statistically from medium MS without growth regulators and from the one supplemented with 4,44 mM of BA.