Abstract
Somatic embryogenesis is an efficient method for the production of target cells for soybean genetic transformation. However, this method still offers low percentages of plant regeneration, and perhaps is related to the maturation process and high morphological abnormalities of the matured embryos. This study aimed to identify a maturation medium that could contribute to the outcome of more efficient plant regeneration results. Embryogenic clusters, derived from cotyledons of immature seeds of the soybean cultivars Bragg and IAS5, were used as starting material for embryos development. Different maturation media were tested by using 6% maltose, 3% sucrose or 6% sucrose, combined with or without 25 g L-1 of the osmotic regulator polyethylene glycol (PEG-8000). The histodifferentiated embryos were quantified and classified in morphological types. Percentages of converted embryos were analyzed. Cultivar Bragg resulted in higher matured embryo quantities, but lower percentages were obtained for the conversion in comparison to cultivar IAS5. While the addition of PEG did not affect the number of embryos converted into plants, 6% sucrose enhanced the conversion percent significantly.
Highlights
Soybean crops are outstanding in the Brazilian agronomical scenery, and for this reason there is a special interest in genetic improvement programs by genetic transformation
The objective of this work was to investigate whether supplementation of the maturation medium with sucrose and Polyethylene glycol (PEG) would improve maturation and conversion frequencies of soybean somatic embryos
The data obtained for the three parameters studied, PEG, carbon sources and cultivars, were analyzed independently
Summary
Soybean crops are outstanding in the Brazilian agronomical scenery, and for this reason there is a special interest in genetic improvement programs by genetic transformation. An important prerequisite is the establishment of an in vitro culture capable of producing highly responsive tissues. First reported in soybean by Christianson et al (1983), is one of the most efficient methods to obtain regenerated plants, either on semi-solid media (Droste et al, 2002) or in liquid suspension cultures (Finer & Nagasawa, 1988; Droste et al, 2001). While a considerable number of protocols describe successfully the induction and proliferation of somatic embryos, the maturation and germination stages remain a goal, due to the low frequency of embryos converted into plants (Droste et al, 2001).
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