Effect of MgSO4 and K2SO4 on somatic embryo differentiation in Theobroma cacao L.

Abstract

Somatic embryogenesis in cacao is difficult and this species is considered as recalcitrant. Therefore, reformulation of culture media might be a breakthrough to improve its somatic embryogenesis. In cacao, acquisition of somatic embryogenesis competence involves three main stages: induction of primary callus, induction of secondary callus and embryo development. Screening for MgSO 4 and K 2 SO 4 concentrations for somatic embryo differentiation was conducted on three genotypes (Sca6, IMC67 and C151-61) at the three stages. The effect of these two salts in culture media appears to be most efficient at the embryo development stage. At this stage, high MgSO 4 (24 mM) and K 2 SO 4 (71.568 mM) in the culture media induced direct somatic embryos on staminodes and petals of the Sca6 and IMC67 genotypes. Media supplemented with 6.0 mM and 12.0 mM MgSO 4 enabled high responsive of explants and produced high proportion of embryos. The positive effect of MgSO 4 and K 2 SO 4 on the acquisition of embryogenesis competence was further tested on seven cacao genotypes reputed as non embryogenic: SNK12, ICS40, POR, IMC67, PA121, SNK64 and SNK10. All these genotypes were able to produce somatic embryos depending on the MgSO 4 concentration. Thus, our results showed that the recalcitrance of cacao to somatic embryo differentiation can be overcome by screening for the suitable MgSO 4 or K 2 SO 4 concentration. Studies of the influence of different K + /Mg 2+ ratios (at normal sulphate concentration) on somatic embryo differentiation revealed that sulphate supply was the main factor promoting responsive explants and the proportion of embryos. Cysteine synthase isoforms showed patterns related to morphogenetic structures sustaining that sulphur supply and its assimilation improve somatic embryogenesis in cacao.

Peroxidase and polyphenol oxidase activities associated to somatic embryogenesis potential in an elite hybrid genotype of Theobroma cacao L.

“…This experiment used the protocol developed by Minyaka et al (2008). Explants were cultured in induction medium and incubated for 14 days in darkness at 25±1°C.…”

“…However, these vegetative propagation methods of cacao lead to plants highly sensitive to winds and dryness in African countries (Tahi et al, 2006). Somatic embryogenesis has been studied by many research teams (Omokolo et al, 1997;Li et al, 1998;Maximova et al, 2002;Traoré et al, 2003;Minyaka, et al, 2008Minyaka, et al, , 2010Minyaka, 2009). Cacao somatic embryogenesis allows rapid vegetative and large-scale multiplication of elite genotypes, genetic improvement, collection and conservation of cacao germoplasm, efficient diffusion of plant material as plantlets to farmers, etc.…”

Pengaruh Komposisi Media Dasar dan Jenis Eksplan terhadap Pembentukan Embrio Somatik Kakao

“…Penurunan semakin besar seiring lamanya kultur diinkubasi dalam media tanpa sulfur (menghilangkan sulfur pada media induksi kalus sekunder serta media induksi dan pendewasaan embrio somatik). Tidak adanya suplai sulfur di dalam media menghambat asimilasi sistein sintase yang penting untuk proses embriogenesis somatik pada kakao (Minyaka et al, 2008).…”

Influence of the position of flowers buds on the tree on somatic embryogenesis of cocoa (Theobroma cacao L.)

“…The tissue system used in this investigation was the same as the system previously described by Minyaka et al (2008). Studies were carried out on the cacao genotype "SCA 6", which is included in the gene-bank of the Institute of Agricultural Research and Development at Nkolbisson (Yaounde, Cameroon).…”