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ABSTRACT:The objective of this study was to promote the establishment of an in vitro culture of Brassavola tuberculata, testing different concentrations of naphthalene acetic acid (NAA) and 6-benzylaminopurine (BAP) on multiplication and rooting, evaluating different substrates during acclimatization, as well as the effect of in vitro treatments. After germination, the seedlings of B. tuberculata were subjected to culture on MS medium supplemented with different concentrations of NAA and BAP, and multiplication and rooting were assessed. During acclimatization, different substrates were tested: S1, Plantmax® and vermiculite (1: 1); S2, Plantmax® and grit (1: 1); and S3, dust fern. Also the effect of the in vitro culture treatments was evaluated: T1, control; T5, (2.5 µM NAA +5 µM BAP); and T7, (5 µM NAA + 0 µM BAP). The favorable balance of cytokinins promoted by treatment T5 yielded the largest number of shoots and leaves in B. tuberculata. The greatest length of leaves and roots, and highest root number were observed in the treatment T7, favored by the presence of auxin. This treatment had a positive effect with respect to plant acclimatization: T7 associated with substrate S1 provided the most suitable conditions for acclimatization of seedlings of B. tuberculata, providing greater number and length of leaves, and high survival rate.

Jatropha curcas L. has been considered one of the most promising alternatives for biofuel production and, thus, a relevant economic crop. In this context, in vitro tissue culture techniques such as organogenesis and embryogenesis have been conducted for mass clonal propagation of elite J. curcas lines. However, despite advancements, in vitro induction of polyploids has not yet been related for this crop. In this sense, the present study attempted to induce polyploidy in plantlets generated from shoot tips of J. curcas 'Gonçalo' (2n = 29 = 22 chromosomes, 2C = 0.85 pg). For this purpose, some criteria were adopted for selection of the most adequate colchicine treatment: (a) survival rate of the explants, and (b) number of tetraploid and (c) mixoploid plantlets. Tetraploid and mixoploid plantlets were obtained from different treatments, with 0.5 mM colchicine for 96 h being the most efficient. The plantlets were recovered and clonally propagated in tissue culture medium supplemented with indole-3-acetic acid and 6-benzylaminopurine. These results show that the tissue culture procedures were adequate for induction, propagation and recovery of tetraploid and mixoploid plantlets. Moreover, DNA ploidy level screening by flow cytometry was a practical and rapid strategy for selection of diploid, mixoploid and tetraploid plantlets. The tissue culture system presented here represents a reliable methodology for in vitro polyploid induction of this and other elite lines of J. curcas.

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