African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12278

Full Length Research Paper

Optimization of somatic embryogenesis procedure for commercial clones of Theobroma cacao L.

Garcia Claudia
  • Garcia Claudia
  • Mars Center for Cocoa Science, Fazenda Almirante, Caixa Postal 55 Itajuípe-BA, CEP 45630-000, Brazil.
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Corrêa Fabio
  • Corrêa Fabio
  • Departamento de Ciências Exatas e Tecnológicas, Universidade Estadual de Santa Cruz, DCET, Ilhéus-BA, CEP 45662-900, Brazil.
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Findley Seth
  • Findley Seth
  • Mars Inc., 13601 Old Cutler Road, Miami, Florida 33158, United States of America.
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Almeida Alex-Alan
  • Almeida Alex-Alan
  • Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, DCB, Ilhéus-BA, CEP 45662-900, Brazil.
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Costa Marcio
  • Costa Marcio
  • Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, DCB, Ilhéus-BA, CEP 45662-900, Brazil.
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Motamayor Juan Carlos
  • Motamayor Juan Carlos
  • Mars Inc., 13601 Old Cutler Road, Miami, Florida 33158, United States of America.
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Schnell Ray
  • Schnell Ray
  • Mars Inc., 13601 Old Cutler Road, Miami, Florida 33158, United States of America.
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Marelli Jean-Philippe
  • Marelli Jean-Philippe
  • Mars Center for Cocoa Science, Fazenda Almirante, Caixa Postal 55 Itajuípe-BA, CEP 45630-000, Brazil.
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  •  Received: 03 June 2016
  •  Accepted: 24 August 2016
  •  Published: 07 September 2016

Abstract

The first objective of this study was to assess and optimize somatic embryo production in a genetically diverse range of cacao genotypes. The primary and secondary somatic embryogenesis response of eight promising cacao clones and a positive control was evaluated using modified versions of standard protocols. The second objective was to optimize the efficiency of primary somatic embryogenesis for a commercially important cacao clone, CCN 51, which has proven to be quite recalcitrant to standard protocols, relative to CCN 10, a clone also included in our analysis. The efficiency of the overall process was assessed by determining the number of somatic embryos produced per starting somatic tissue explant, as well as the quality of embryos (normal vs. abnormal) produced. Donor floral explants were subjected to five tissue culture steps, each 15-25 days in duration. Although all studied genotypes produced primary somatic embryos, most of them originated only from brown or brown-white callus. Overall, flower petals performed better than staminodes, and our best performing genotype yielded an average of 7-10 embryos produced in brown callus explants with embryogenic response during primary somatic embryogenesis procedures. In conclusions our analysis from a pilot in a small-scale are: 1) it is possible to achieve a high production of plants by somatic embryogenesis, although the efficiency is highly genotype-dependent; it is therefore necessary to optimize hormone balance and hormone type, as well as the explant type for each genotype, 2) through the use of secondary somatic embryogenesis, it is possible to increase somatic embryogenesis production at least ten-fold, and 3) the observed response variation between genotypes may reflect differences in endogenous and exogenously-supplied hormones. The importance of adapting the tissue culture protocol to the genotype is discussed.

Key words: Somatic embryogenesis, 2,4-D, cellular competence, propagation, abnormalities, ethylene, cacao.

Abbreviation

2,4-D, 2,4-Dichlorophenoxyacetic acid; 2,4,5-T, 2,4,5-trichlorophenoxyacetic acid; BAP, 6-benzylaminopurine; TDZ, thidiazuron; IAA, indole-3-acetic acid; IBA, indole-3-butyric acid; SE, somatic embryogenesis; SEs, somatic embryos; PGRs, plant growth regulators; PSE, primary somatic embryogenesis; PSEs, primary somatic embryos; SSE, secondary somatic embryogenesis; SSEs, secondary somatic embryos; PGC, primary callus growth; SCG, secondary callus growth; ED4, embryos development-4; ED3, embryos development-3; ED, embryo development; EE, efficiency of embryogenesis; EDL, embryo development in light; PEC, primary embryo conversion.