Thidiazuron-induced direct organogenesis from immature inflorescence of three date palm cultivars

Background Inflorescence explants of date palm proved to be a promising tool for micropropagation of elite cultivars or rare males and females as organogenesis and somatic embryogenesis could be achieved. These plant materials are abundantly available every year and can be used as cheap and potent explants. Nevertheless, many difficulties could be faced in this protocol according to selection of the spathe size and age, media components, growth regulators, etc. The aim of this study was to determine the influence of various cytokinins on direct organs induction of three date palm cultivars (Selmi, Barhee, and Medjool) from immature inflorescence. An additional objective of this study was to investigate the effect of cytokinins and auxins on growth and development of Medjool cultivar. Results Various combinations of cytokinins were investigated on three date palm inflorescences as N6-(2-isopentenyl) adenine (2iP), kinetin, benzyleadenine (BA), and thidiazuron (N-phenyl-N′-1,2,3-thidiazol-5-yl urea) (TDZ). TDZ alone or in combination with BA proved to be superior for direct organogenesis in all three cultivars so that another combination of TDZ with BA was conducted. Results showed that moderate concentration of BA, with TDZ, gave superior response. Medjool cultivar response surpassed other two cultivars that made the possibility to conduct some growth regulators treatments on its multiplication and regeneration. TDZ at 0.5 + BA at 1.0 mg/l without activated charcoal seemed to enhance multiplication rate. Medium containing 0.5 mg/l of both naphthaleneacetic acid and indole butyric acid in addition to 1.0 mg/l indole acetic acid appeared to be more suitable for rooting stage of Medjool shootlets. Conclusion In this study, we created an innovation sequence of growth regulators included in nutrient media for date palm direct organogenesis from inflorescence. Organogenesis has been accelerated from immature inflorescence explants and developed to healthy plantlets which acclimatized in greenhouse.

In Vitro Induction of Callus and Flowers in Immature Oil Palm Inflorescences

This work aimed to investigate the effects of different combinations of auxin (0, 225 and 450 µM Picloram) and Murashige and Skoog salts (50% and 100% MS salt concentrations, respectively named as ½ MS and MS) in mediate the induction of callus and flowers from immature inflorescences (developmental stages I-9, I-12 and I-15) of the oil palm BRS – Manicoré hybrid. In I-9 inflorescence explants, the rate of callus induction was 17% higher in ½ MS than in MS; while in both I-12 and I-15 inflorescence explants, callus induction was over than 95% regardless of the MS salt concentration. The higher rate of callus induction in I-9 inflorescences was mediated by 450 µM Picloram, while the callus induction rates for either I-12 or I-15 inflorescences were higher than 92% regardless of Picloram concentration. Floral induction was lower in I-9 inflorescence explants (45% floral induction rate) than in both I-12 and I-15 inflorescence explants (floral induction rate higher than 90%). Our results suggest that Picloram (450 µM) and MS salts concentrations (½ MS) led to the highest rates of calluses and flowers induction in younger inflorescence explants (I-9); however, the medium composition is indifferent on callus and flower induction in I-12 and I-15 inflorescences.

In vitro response of date palm (Phoenix dactylifera L.) inflorescence explants to high 2iP and 2,4-D concentrations

One of the major problems related to the implementation of date palm crops in Brazil is propagation. Therefore, the aim of this study was to evaluate the possibility of using tissue culture technique for the in vitro propagation of this species. Hence, the effect of 2iP and 2,4-D on the in vitro response of date palm inflorescence tissues, related to floral bud swelling, callusing, and rhizogenesis, was evaluated. The absence of 2,4-D was more detrimental to the in vitro response of inflorescence bud explants than absence of 2iP. In treatments without addition of 2,4-D to the culture medium, explants did not have swelling, callus or root formation. The treatment containing 150 mg/L 2,4-D in the presence of 1.5 mg/L 2iP initiated explant swelling, and treatments with either 100 mg/L or 150 mg/L 2,4-D, combined with 3.0 mg/L 2iP, were also efficient in stimulating in vitro swelling of inflorescence buds. Rhizogenesis was induced at the highest concentrations of 2,4-D (100 and 150 mg/L), combined with 4.5 mg/L 2iP, and was visually more evident in the treatment containing 150 mg/L 2,4-D + 4.5 mg/L 2iP. These results suggest that even higher concentrations of these two reagents might be efficient in the micropropagation of new existing date palm genotypes in the Submedium São Francisco River Valley.