Browsing by Author "Abdourahamane Sangare"

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    Characterization of Callogenic and Embryogenic Abilities of Some Genotypes of Cocoa (Theobroma cocoa L.) Under Selection in Cote d lvoire
    (Asian Network for Scientific Information, 2008) Auguste Emmanuel Issali; Abdoulaye Traore; Eclmond Kouablan Koffi; Jeanne Andi Kohi N goran; Abdourahamane Sangare
    To optimize the somatic embryogenesis, a characterization in vitro by an improved process of some cocoa genotypes was undertaken. Six hybrids, five parents and two clones as control were used. Staminodes and petals were cultured on three primary callus growth media (PCG) differing in hormonal balance 2.4-D/TDZ. Two primary descriptors (callogenic and embiyogenic explant number) and three secondary descriptors (general abilities, favourable explants and PCG media) were used to characterize studied genotypes. The separate characterization of factors from two primary descriptors, allowed identifying of four hybrids (L233-A4, L231-A4, LI 20-A2 and LI 26-A3), three parents (PI 9A, Pal 3 and IMC67) and two control clones (CI 51 -61 and SCA6) as both callogenic and embryogenic. Petals proved to be the best embiyogenic explant. PCG1 medium was both callogenic and embryogenic. The improved characterization by combination of factors from primary descriptors generated three secondary descriptors. This combination of factors allowed refining the characterization by identifying not only the best explant but also the best medium for expression of each genotype. The approach used here allows an accurate characterization of genotype and might be helpful in the regeneration in plantlets of superior genotypes of cocoa.
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    Effect of MgSO4 and K2SO4 on somatic embryo differentiation in Theobroma cacao L
    (2008) Emile Minyaka; Nicolas Niemenak; Fotso; Abdourahamane Sangare; Denis Ndoumou Omokolo
    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 MgSO4 and K2SO4 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 MgSO4 (24 mM) and K2SO4 (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 MgSO4 enabled high responsive of explants and produced high proportion of embryos. The positive effect of MgSO4 and K2SO4 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 MgSO4 concentration. Thus, our results showed that the recalcitrance of cacao to somatic embryo differentiation can be overcome by screening for the suitable MgSO4 or K2SO4 concentration. Studies of the influence of different K+/Mg2+ 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.
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    Implication of Bacillus sp. in the production of pectinolytic enzymes during cocoa fermentation
    (2008) Abdourahamane Sangare; Ban L. Koffi; Germain T. Karou; Honore G. Ouattara; Sebastien L. Niamke; Jacques K. Diopoh
    The role of bacilli in cocoa fermentation is not well known. Their potential of production of pectinolytic enzymes during this process was evaluated. Bacillus growth was monitored and pectinolytic strains were screened for their use of pectin as sole carbon source. Effects of cocoa fermentation parameters susceptible to influence on enzyme production were analysed. Among 98 strains isolated, 90 were positive for pectin degradation and 80% of them presented detectable pectinolytic activities in submerged fermentation. Forty-eight strains produced polygalacturonase (PG), 47 yielded pectin lyase (PL) and 23 strains produced both enzymes. Bacilli growth was not significantly affected during fermentation. PL production was favoured by galactose, lactose, glucose as sugars, and arginine, glutamine, cysteine and ammonium sulphate as nitrogen compounds. Pectin at low concentration (0.05%) and iron stimulated PL production. It was strongly repressed by galacturonic acid (1%), and negatively affected by nitrogen starvation, zinc and temperatures above 45 C. PL yield was very weak below pH 4.0 and in anaerobic conditions. PG production was weakened by sucrose and cation depletion. It was increased slightly by cysteine, ammonium nitrate and nitrogen starvation and significantly above 40 C. PG synthesis was not affected by acidic pH (3.0–6.0) or oxygen availability. As fermentation products, lactate and acetate lowered the production of both enzymes while ethanol had no effect. The high proportion of pectinolytic producers among the strains studied and analysis of factors influencing pectinolytic enzymes production, suggest that Bacillus sp. is liable to produce at least one enzyme during cocoa fermentation.