Abstract
The study aims to compare the efficiency of previously used liquid media for coffee, evaluating NAA concentrations in liquid medium and proline in semi-solid medium in the regeneration of somatic embryos and asses concentrations of BA and IAA in the maturation of embryos in temporary immersion bioreactors. For the regeneration of globular embryos from embryogenic aggregates and calli, we tested five concentrations (0.00, 0.25, 0.50, 1.00 and 2.00 mg L-1) of NAA in liquid medium and five concentrations (0.0, 0.5, 1.0, 2.0 and 4.0 g L-1) of proline in semisolid medium. The multiplication of embryogenic aggregates was highest in culture medium MM, reaching a density 7.5 times greater than that of the initial density. NAA promoted a linear increase in embryo regeneration. The medium containing 2.0 mg L-1 BA and 0.0 mg L-1 IAA yielded the highest percentage of large cotyledonary embryos.
Highlights
The vegetative propagation of coffee (Coffea arabica L.) via somatic embryogenesis facilitates the rapid evaluation of F1 hybrids and segregating genotypes in genetic breeding programs, allowing clonal varieties to be developed in only 10 years (Caixeta et al 2008, Salgado et al 2014)
Large-scale multiplication via somatic embryogenesis has been used for the dissemination of F1 hybrids with high levels of heterosis in Central America (Bertrand et al 2011) and is becoming a reality in Mexico (Etienne et al 2013) and Brazil (Carvalho et al 2013), in part due to advances in the use of temporary immersion bioreactors for the production of pregerminated embryos (Ducos et al 2007b)
It should be noted that the concentration of 2,4-D in the MM medium was not appreciably higher than that in the T3 medium, 0.50 and 0.45 mg L-1, respectively, because high concentrations of 2,4-D have been associated with somaclonal variation in coffee plants regenerated from tissue cultures (Duncan 1998), which is undesirable for commercial propagation
Summary
The vegetative propagation of coffee (Coffea arabica L.) via somatic embryogenesis facilitates the rapid evaluation of F1 hybrids and segregating genotypes in genetic breeding programs, allowing clonal varieties to be developed in only 10 years (Caixeta et al 2008, Salgado et al 2014). Large-scale multiplication via somatic embryogenesis has been used for the dissemination of F1 hybrids with high levels of heterosis in Central America (Bertrand et al 2011) and is becoming a reality in Mexico (Etienne et al 2013) and Brazil (Carvalho et al 2013), in part due to advances in the use of temporary immersion bioreactors for the production of pregerminated embryos (Ducos et al 2007b). While the cost-effectiveness of somatic embryogenesis for commercial coffee propagation remains unsatisfactory, profitability could be enhanced by optimizing the multiplication protocol decreasing the production cost per somatic seedling (Etienne et al 2013). For embryogenic callus multiplication, Teixeira et al (2004) suggested the use of 1.0 mg L-1 2,4-dichlorophenoxyacetic acid (2,4-D), 1.0 mg L-1 indolebutyric acid (IBA), and 2.0 mg L-1 2-isopentenyl adenine (2-ip), while Menéndez-Yuffá et al (2010) and Etienne et al (2005) used 1.0 mg L-1 2,4-D and 1.0 mg L-1 kinetin.
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