Abstract
ABSTRACT Oil palm is economically important as a crop with high oil production. Indirect somatic embryogenesis in oil palm requires a long time for callus induction and plant formation, and it is important to study the embryogenic potential of calli and the mechanisms of somatic embryogenesis. The aim of this study was to test different growth regulators and spermine in induction of embryogenic calli in root explants of oil palm (Elaeis guineensis Jacq). Apex root explants of approximately 0.5 cm were isolated from plants cultivated in vitro and inoculated in Y3 culture medium in the following treatments: A - without growth regulators; B - 1 mg.L-1 picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid); C - 1 mg.L-1 picloram and 2 mg.L-1 2ip (2-isopentenyladenine); D - 2 mg.L-1 2ip; E - 1 mg.L-1 picloram and 2 mg.L-1 BAP (6-benzylaminopurine); F - 2 mg.L-1 BAP; and G - 14.5 mg.L-1 spermine. After six months of culturing, the calli induced in the treatments were analyzed by light microscopy. The calli induced in the treatments with 1 mg.L-1picloram (B) and treatment with 14.5 mg.L-1spermine (G) exhibited embryogenic characteristics, small and isodiametric cells, forming agglomerates, besides a large amount of starch. Calli of the best treatment (Y3 com 1 mg.L-1 de picloram) were inoculated in Y3 culture medium without addition of growth regulators. After eight months, calli were once more analyzed under light microscopy. All the treatments showed callus formation, except for treatments D and A. Calli of treatment B exhibited cells with embryogenic characteristics that developed somatic embryos.
Highlights
Oil palm stands out among oilseeds through the large quantity and good quality of oil produced by its bunches in comparison with other oilseeds, for example, soybean, which produces approximately 400 kg per hectare, whereas oil palm produces approximately 6,000 kg per hectare, with low production cost (Agrianual, 2012)
Indirect somatic embryogenesis in oil palm requires a long time for callus induction and plant formation, and it is important to study the embryogenic potential of calli and the mechanisms of somatic embryogenesis
Callus formation in roots explants was observed in all the culture media supplemented with growth regulators, except for culture medium D, supplemented with 2 mg.L-1 of 2iP
Summary
Oil palm stands out among oilseeds through the large quantity and good quality of oil produced by its bunches in comparison with other oilseeds, for example, soybean, which produces approximately 400 kg per hectare, whereas oil palm produces approximately 6,000 kg per hectare, with low production cost (Agrianual, 2012). Due to wide use of oil palm, it is important to expand crop area; seedlings are scarce on a commercial scale because of limitation of having a single apical meristem per plant, which makes propagation by conventional methods such as cuttings impossible. An alternative for seedling production on a commercial scale that is becoming more prominent for palm species is tissue culture through somatic embryogenesis. During the somatic embryogenesis process, growth regulators are necessary for dedifferentiation during callus formation and differentiation for formation of somatic embryos. Picloram stands out among these growth regulators used to callus induction in palm (Steinmacher et al, 2007; Moura et al, 2008; Pádua et al, 2013; Mazri et al, 2018). The association of auxins with cytokines an favor callus formation, as observed in Paspalum vaginatum Flüggé (Neibaur and Altpeter, 2008) and Elaeis guineensis Jacq (Silva et al, 2009; Balzon, 2013)
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