Emile MINYAKA - Academia.edu (original) (raw)

Papers by Emile MINYAKA

International Journal of Sustainable Agricultural Research

S. platensis is a cyanobacterium known for its richness in protein and bioactive compounds, with ... more S. platensis is a cyanobacterium known for its richness in protein and bioactive compounds, with very captivating therapeutic and nutritional properties. In Cameroon, the medium commonly used for the cultivation of S. platensis is Jourdan's medium which is expensive and less available. Thus, it is necessary to find an alternative medium that is more efficient, less expensive and more available. Nutrients present in agro-industrial by-products can be used to enhance the production of biomass and photosynthetic pigments of S. platensis. Therefore, this study was conducted to evaluate the growth and Photosynthetic pigments productivity of S. platensis on the Oil Palm Empty Fruit Bunch (OPEFB) medium. The culture medium was formulated by distilling different concentrations (0; 2; 4; 6; 8 and 10 g L-1) of ash from previously dried and incinerated OPEFB medium in distilled water. The highest optical density (1.01 ± 0.09), dry biomass (1.35 ± 0.10 g L-1) and productivity (0.032 g L-1d-...

African Journal of Biotechnology, Oct 4, 2010

To analyse the relationship between climatic parameters and somatic embryogenesis (SE), some favo... more To analyse the relationship between climatic parameters and somatic embryogenesis (SE), some favourable and unfavourable periods were identified. Likewise, to optimize SE in unfavourable periods the relationship among 2,4-D/TDZ, SE and year was analysed. Staminodes and petals of six hybrids and two clones as controls were sown in bulk onto three different calli induction media. Minimal temperature, rainfall, maximal temperature, mean temperature, temperature gaps, sunshine and relative humidity as climatic parameters were simultaneously recorded the day of the harvest of flower buds. Student-Fisher's test at 5% level, Principal Component Analysis and Pearson's linear correlation at 5%, 1% or 1‰ were used to separate the averages, identify the best climatic parameters and analyse the link between the climate and SE, respectively. The relative humidity and mean temperature were eliminated from the study. The period that spreads out from January to September favoured SE. In favourable periods, the SE variation was independent of that of concentration in 2,4-D/TDZ. This shows that these are the metabolites coming from 2,4-D/TDZ that activate the genes rather than these two compounds themselves. In unfavourable periods, in the first year, the weakest concentration in 2,4-D/TDZ of PCG3 medium favoured SE, while in the second year that is the strongest concentration of PCG4 which increased it. This could indicate an interaction among year, concentration in 2,4-D/TDZ and SE. However, the link thus established is only statistical. It did not allow the quantification of the contribution level of these climatic parameters to variations of SE.

International Journal of Nutrition and Food Sciences

IOP Conference Series: Materials Science and Engineering, 2017

The ability of water and sodium bicarbonate solution in producing debittering cocoa bean for imme... more The ability of water and sodium bicarbonate solution in producing debittering cocoa bean for immediate consumption as ready to cook food and the applicability of empirical Peleg model in order to interpret the sorption data is evaluated in this study. Fermented cocoa beans were soaked and/or boiled in water and in 2% sodium bicarbonate solution with a weight to volume ratio of 1:10. Cocoa beans were withdrawn at each interval over a 6-h time period and moisture and minerals (calcium, magnesium, phosphorus and potassium) content analyzed using standard analytical methods. Bitterness was measured by sensory analysis. Peleg model was used to transform the sorption data into the mathematical equation and Peleg parameters K 1 , K 2 and M e calculated. It has been found that boiling in water and sodium bicarbonate (2%) significantly reduces the bitterness of cocoa beans. Kinetic curves of water absorption express the characteristic shape with a fast water absorption rate at the beginning of the process follow by a decreasing rate as the equilibrium moisture is reached. Mineral desorption curves exhibited unusual pattern depending on the mineral under consideration. Application of sorption data demonstrates a predictive capacity of the Peleg model as judged by the regression coefficients. Boiling cocoa beans for 50 min in 2% sodium bicarbonate and 30 min in boiling water can be considered as optimal for debittering cocoa beans in order to give them palatable option to be integrated in nutrition and in none medicinal therapeutics in Cameroon.

Plant Biotechnology Reports

The induction, development, and maturation of somatic embryos in cocoa are subjected to numerous ... more The induction, development, and maturation of somatic embryos in cocoa are subjected to numerous failures during the various development stages. Understanding the biochemical/molecular events governing somatic embryogenesis in T. cacao will help to overcome these failures. The present study focused on cocoa somatic embryogenesis proteomic variations with the aim to shed light on the constraints of somatic embryos during their development stages (induction, expression, and maturation). These were investigated using combinations of LC–MS/MS coupled with TripleTOF 5600 + and Orbitrap Fusion methods during cocoa (Theobroma cacao L.) somatic embryogenesis. Non-embryogenic callus (NC), embryogenic callus (EC), somatic embryos (ESN), and zygotic embryos (EZM) were used as samples. Sample analyses followed by bioinformatics research identified a total of 1762 proteins. The differentially expressed proteins (DEPs) were derived from NC (429), EC (301), ESN (911), and EZM (511) and classified according to ontological categories. The analysis of KEGG pathways in NC and EZM showed that they were mainly enriched in metabolic pathways and the biosynthesis of secondary metabolites. While in EC and ESN, they are enriched in endoplasmic reticulum protein processing. Based on protein–protein interaction analysis, proteins in EC and ESN were highly regulated and involved in environmental stress. On the other hand, proteins in NC and EZM, highly regulated were involved in energy metabolism. This proteomic study provides clues to understand the low rate of conversion to plant in somatic embryogenesis and helps to build a model for improved culture medium.

Environmental science and pollution research international, Jan 26, 2018

Cocoa black pod disease caused by Phytophthora megakarya and reduced soil fertility are major con... more Cocoa black pod disease caused by Phytophthora megakarya and reduced soil fertility are major constraints to cocoa production resulting in high yield losses. In the absence of effective control measures and constraints related to the use of chemical fungicides and fertilizers, there is a need to develop additional and sustainable disease and fertilization management strategies. With the lack of studies related to the use of compost in cocoa cultivation, the present study aims to evaluate the potential of cocoa pod husk (CPH)-based compost as a soil amendment to reduce the severity of cocoa black pod disease and enhance plant growth. In vitro antagonism test showed that compost water extracts (CWE) reduced mycelial growth with inhibition rate reaching 100% associated with microorganisms. Disease score of cocoa plantlets grown on compost-amended soils significantly reduced compared to plantlets grown on non-amended soil (control). All compost rates tested significantly increased popul...

African Journal of Biotechnology, 2021

The prospects for using Moringa oleifera leaves extract (MLE) supplemented with different concent... more The prospects for using Moringa oleifera leaves extract (MLE) supplemented with different concentrations of kanwa or sodium bicarbonate (NaHCO 3) as a low-cost alternative growth medium of Spirulina platensis were evaluated in a small-scale outdoor cultivation system. The present study was aimed to evaluate the potential of MLE growth medium enriched with different concentrations (4 or 8 g L-1) of kanwa and NaHCO 3 on growth, chlorophyll content, biochemical characteristics, antioxidant compounds and some physico-chemical factors. Jourdan's standard medium was taken as control. The results showed that the growth parameters such as cell population, biomass dry weight, cell productivity and specific growth rate were positively affected in MLE cultivation medium enriched with kanwa or NaHCO 3 at different concentration levels. The addition of urea, kanwa or NaHCO 3 in MLE cultivation medium at different concentration levels increased significantly (p< 0.05) the protein content, the peroxidase and polyphenol oxidase activity, the conductivity, pH, total dissolved solids and salinity from 20 to 25 days of cultivation whereas a decrease in carbohydrate and phenol content was recorded during all the period of the experimentation. The highest values of growth parameters were notably in MLE medium supplemented with urea and kanwa at 8 g L-1. The MLE medium enriched with urea and kanwa at 8 g L-1 was shown to be an appropriate growth medium that can be used as a lowcost alternative growth medium for commercial cultivation of S. platensis.

Plant Cell, Tissue and Organ Culture, 2008

Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate p... more Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate plants-associated defence markers in plantlets leaves are decisive for development of T. cacao genotypes tolerant to black pods disease (BPD). T. cacao plantlets from manual cross-pollination of ♀SNK64 × ♂UPA143 were analyzed for their susceptibility to BPD using leaf disc test. Subsequently, leaves (healthy, wounded and wound+infected) of selected E9 (tolerant), E13 (moderate susceptible) and E32 (most susceptible) young hybrid genotypes from ♀SNK64 × ♂UPA143 were used for flavones analysis using a HPLC/LC/MS system. Leaf disc test showed 62.5% of the progeny with disease score rates lower than the mean value of both parents. About 79.17% and 20.83% of the progeny were lesser susceptible than the most susceptible parent (UPA143) and the tolerant parent (SNK64) respectively. Total flavones contents were abiotic and biotic stresses-dependant. Under infection, tolerant hybrid genotype (E9) ...

African Journal of Biotechnology, 2017

Black pod disease (BPD) is the major cocoa pathology constraint caused by an Oomycete, Phytophtho... more Black pod disease (BPD) is the major cocoa pathology constraint caused by an Oomycete, Phytophthora megakarya prevailing in African cocoa producing countries. The development of T. cacao planting material tolerant to BPD lies on cross-pollination of adequate parental genotypes which generate offspring with desirable traits. We assessed the susceptibility to BPD of offspring derived from three manual crosses (SNK13xUPA143, T79/501xUPA143 and UPA143xSNK64) using leaf discs test (LDT) which evaluates disease scores of hybrid genotypes. Cysteine involvement in T. cacao defence process against BPD has been studied for the potential use of this sulphur amino acid profile to identify tolerant cocoa hybrid genotypes. LDT displayed variable disease scores patterns. Within a given family, LDT revealed heterogeneity in disease scores. This heterogeneity may have been derived from polygenic character of T. cacao susceptibility to BPD. In SNK13xUPA143 family, 26.13% exhibited disease scores lowe...

Journal of the Cameroon academy of sciences, 2004

Plant protection science, 2017

Minyaka E., Madina Banen C.V., Kusznierewicz B., Doungous O., Haouni S., Hawadak J., Niemenak N.,... more Minyaka E., Madina Banen C.V., Kusznierewicz B., Doungous O., Haouni S., Hawadak J., Niemenak N., Omokolo D.N. (2018): Effect of MgSO4 nutrition on Theobroma cacao susceptibility to Phytophthora megakarya infection. Plant Protect. Sci., 54: 74–82. A new strategy to reduce the severity of black pod disease (BPD) in T. cacao plants using MgSO4 nutrition was investigated. The dynamics of the tolerance to BPD of 18 susceptible T. cacao plantlets coming from the cross (♀SNK64 × ♂UPA14) was monitored during weekly (8 weeks) supply of MgSO4 into the soil. Prior to MgSO4 application, disease scores of the 18 plantlets (in six sets of three plantlets per set) were varying between 3.5 (susceptible) and 5 (highly susceptible). After MgSO4 application, a substantial decrease in disease scores was observed compared to the control. The percentage of disease tolerance gain of plantlets versus MgSO4 supplied (0–2.96 g) presented a quasi-hyperbolic curve with asymptotic line corresponding to 60% (da...

1Department of Plant Biology, Faculty of Science, University of Douala, PO Box 24157 Douala, Came... more 1Department of Plant Biology, Faculty of Science, University of Douala, PO Box 24157 Douala, Cameroon. 2Department of Plant Biology, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon. 3Department of Biochemistry, Faculty of Science, University of Douala, PO Box 24157 Douala, Cameroon. 4Laboratory of Plant Physiology, Department of Biological Sciences, Higher Teacher’s Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon.

Develop T. cacao hybrid genotypes tolerant to P. megakarya is the way out to improve cocoa produc... more Develop T. cacao hybrid genotypes tolerant to P. megakarya is the way out to improve cocoa production and profitability in cocoa producing countries. Hence, the analysis of susceptibility to P. megakarya of the progeny ♀SNK64x♂UPA143 was conducted for the first time. Additionally, cysteine content and myrosinase activity were analyzed in healthy, wounded and wounded_infected leaves in other to bring out the implication of cysteine and myrosinase in T. cacao defense against P. megakarya. The screening for susceptibility to P. megakarya of the progeny ♀SNK64x♂UPA143 has revealed that, more than 58 % of the progeny ♀SNK64x♂UPA143 displayed negative Mid-Parent Heterosis (MPH) and around 79 % were less sensitive to black pod disease than the most sensitive parent UPA143. This set of results indicates that the progeny ♀SNK64x♂UPA143 might be recommended for development of T. cacao hybrid genotypes tolerant or less sensitive to black pod disease. Cysteine content in healthy leaves signific...

Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate p... more Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate plants-associated defence markers in plantlets leaves are decisive for development of T. cacao genotypes tolerant to black pods disease (BPD). T. cacao plantlets from manual cross-pollination of ♀SNK64 × â™‚UPA143 were analyzed for their susceptibility to BPD using leaf disc test. Subsequently, leaves (healthy, wounded and wound+infected) of selected E9 (tolerant), E13 (moderate susceptible) and E32 (most susceptible) young hybrid genotypes from ♀SNK64 × â™‚UPA143 were used for flavones analysis using a HPLC/LC/MS system. Leaf disc test showed 62.5% of the progeny with disease score rates lower than the mean value of both parents. About 79.17% and 20.83% of the progeny were lesser susceptible than the most susceptible parent (UPA143) and the tolerant parent (SNK64) respectively. Total flavones contents were abiotic and biotic stressesdependant. Under infection, tolerant hybrid genotyp...

Cross-fertilization and somatic embryogenesis stand as potential useful tools for genetic improve... more Cross-fertilization and somatic embryogenesis stand as potential useful tools for genetic improvement and vulgarization of agronomical interesting cocoa planting material for sustainable cocoa culture. Manual cross-fertilization (♀SNK13×♂UPA143) was conducted. ♀SNK13×♂UPA143 derived hybrid genotypes were tested for their susceptibility to black pods disease (BPD). The most tolerant hybrid genotype (KHACa12) was monitored for its precocity, yielding and somatic embryo potential. Peroxidase and polyphenol oxidase activities were evaluated in association to embryogenesis in KHACa12. The cross-fertilization ♀SNK13×♂UPA143 generated around 60% of offprint’s tolerant or less susceptible to BPD. When transferred in experimental farm, KHACa12 produced flowers 18 months after planting. Mature pods from KHACa12 bearded 55±5 seeds/pod. Seventy-five pods were harvested from KHACa12 during the first season. These pods generated 6 kg of fermented-dried cocoa seeds. Somatic embryo responsive revea...

Somatic embryogenesis is a useful tool for Theobroma cacao improvement and propagation. Depending... more Somatic embryogenesis is a useful tool for Theobroma cacao improvement and propagation. Depending on culture medium composition, different morphogenetic structures (including somatic embryo) occur in response to alteration of genes expression patterns and biochemical changes. The effect of SO 4 2 - ion deficiency in culture media on somatic embryogenesis was studied through sequential replacement of MgSO 4 and K 2 SO 4 by MgCl 2 and KCl, respectively, at different steps of somatic embryogenesis. It appears that explants gradually lost their embryogenic competence as the period of exposition to sulphur free medium increases. These results suggest that, sulphur availability and the duration to sulphur exposition might modulate the expression of genes involved in somatic embryo differentiation in T. cacao . Cysteine, glutathione, reducing sugars, cysteine synthase and cysteine desulfurase activities were analysed in different morphogenetic structures obtained in vitro . Cysteine and re...

International Journal of Sustainable Agricultural Research

S. platensis is a cyanobacterium known for its richness in protein and bioactive compounds, with ... more S. platensis is a cyanobacterium known for its richness in protein and bioactive compounds, with very captivating therapeutic and nutritional properties. In Cameroon, the medium commonly used for the cultivation of S. platensis is Jourdan's medium which is expensive and less available. Thus, it is necessary to find an alternative medium that is more efficient, less expensive and more available. Nutrients present in agro-industrial by-products can be used to enhance the production of biomass and photosynthetic pigments of S. platensis. Therefore, this study was conducted to evaluate the growth and Photosynthetic pigments productivity of S. platensis on the Oil Palm Empty Fruit Bunch (OPEFB) medium. The culture medium was formulated by distilling different concentrations (0; 2; 4; 6; 8 and 10 g L-1) of ash from previously dried and incinerated OPEFB medium in distilled water. The highest optical density (1.01 ± 0.09), dry biomass (1.35 ± 0.10 g L-1) and productivity (0.032 g L-1d-...

African Journal of Biotechnology, Oct 4, 2010

To analyse the relationship between climatic parameters and somatic embryogenesis (SE), some favo... more To analyse the relationship between climatic parameters and somatic embryogenesis (SE), some favourable and unfavourable periods were identified. Likewise, to optimize SE in unfavourable periods the relationship among 2,4-D/TDZ, SE and year was analysed. Staminodes and petals of six hybrids and two clones as controls were sown in bulk onto three different calli induction media. Minimal temperature, rainfall, maximal temperature, mean temperature, temperature gaps, sunshine and relative humidity as climatic parameters were simultaneously recorded the day of the harvest of flower buds. Student-Fisher's test at 5% level, Principal Component Analysis and Pearson's linear correlation at 5%, 1% or 1‰ were used to separate the averages, identify the best climatic parameters and analyse the link between the climate and SE, respectively. The relative humidity and mean temperature were eliminated from the study. The period that spreads out from January to September favoured SE. In favourable periods, the SE variation was independent of that of concentration in 2,4-D/TDZ. This shows that these are the metabolites coming from 2,4-D/TDZ that activate the genes rather than these two compounds themselves. In unfavourable periods, in the first year, the weakest concentration in 2,4-D/TDZ of PCG3 medium favoured SE, while in the second year that is the strongest concentration of PCG4 which increased it. This could indicate an interaction among year, concentration in 2,4-D/TDZ and SE. However, the link thus established is only statistical. It did not allow the quantification of the contribution level of these climatic parameters to variations of SE.

International Journal of Nutrition and Food Sciences

IOP Conference Series: Materials Science and Engineering, 2017

The ability of water and sodium bicarbonate solution in producing debittering cocoa bean for imme... more The ability of water and sodium bicarbonate solution in producing debittering cocoa bean for immediate consumption as ready to cook food and the applicability of empirical Peleg model in order to interpret the sorption data is evaluated in this study. Fermented cocoa beans were soaked and/or boiled in water and in 2% sodium bicarbonate solution with a weight to volume ratio of 1:10. Cocoa beans were withdrawn at each interval over a 6-h time period and moisture and minerals (calcium, magnesium, phosphorus and potassium) content analyzed using standard analytical methods. Bitterness was measured by sensory analysis. Peleg model was used to transform the sorption data into the mathematical equation and Peleg parameters K 1 , K 2 and M e calculated. It has been found that boiling in water and sodium bicarbonate (2%) significantly reduces the bitterness of cocoa beans. Kinetic curves of water absorption express the characteristic shape with a fast water absorption rate at the beginning of the process follow by a decreasing rate as the equilibrium moisture is reached. Mineral desorption curves exhibited unusual pattern depending on the mineral under consideration. Application of sorption data demonstrates a predictive capacity of the Peleg model as judged by the regression coefficients. Boiling cocoa beans for 50 min in 2% sodium bicarbonate and 30 min in boiling water can be considered as optimal for debittering cocoa beans in order to give them palatable option to be integrated in nutrition and in none medicinal therapeutics in Cameroon.

Plant Biotechnology Reports

The induction, development, and maturation of somatic embryos in cocoa are subjected to numerous ... more The induction, development, and maturation of somatic embryos in cocoa are subjected to numerous failures during the various development stages. Understanding the biochemical/molecular events governing somatic embryogenesis in T. cacao will help to overcome these failures. The present study focused on cocoa somatic embryogenesis proteomic variations with the aim to shed light on the constraints of somatic embryos during their development stages (induction, expression, and maturation). These were investigated using combinations of LC–MS/MS coupled with TripleTOF 5600 + and Orbitrap Fusion methods during cocoa (Theobroma cacao L.) somatic embryogenesis. Non-embryogenic callus (NC), embryogenic callus (EC), somatic embryos (ESN), and zygotic embryos (EZM) were used as samples. Sample analyses followed by bioinformatics research identified a total of 1762 proteins. The differentially expressed proteins (DEPs) were derived from NC (429), EC (301), ESN (911), and EZM (511) and classified according to ontological categories. The analysis of KEGG pathways in NC and EZM showed that they were mainly enriched in metabolic pathways and the biosynthesis of secondary metabolites. While in EC and ESN, they are enriched in endoplasmic reticulum protein processing. Based on protein–protein interaction analysis, proteins in EC and ESN were highly regulated and involved in environmental stress. On the other hand, proteins in NC and EZM, highly regulated were involved in energy metabolism. This proteomic study provides clues to understand the low rate of conversion to plant in somatic embryogenesis and helps to build a model for improved culture medium.

Environmental science and pollution research international, Jan 26, 2018

Cocoa black pod disease caused by Phytophthora megakarya and reduced soil fertility are major con... more Cocoa black pod disease caused by Phytophthora megakarya and reduced soil fertility are major constraints to cocoa production resulting in high yield losses. In the absence of effective control measures and constraints related to the use of chemical fungicides and fertilizers, there is a need to develop additional and sustainable disease and fertilization management strategies. With the lack of studies related to the use of compost in cocoa cultivation, the present study aims to evaluate the potential of cocoa pod husk (CPH)-based compost as a soil amendment to reduce the severity of cocoa black pod disease and enhance plant growth. In vitro antagonism test showed that compost water extracts (CWE) reduced mycelial growth with inhibition rate reaching 100% associated with microorganisms. Disease score of cocoa plantlets grown on compost-amended soils significantly reduced compared to plantlets grown on non-amended soil (control). All compost rates tested significantly increased popul...

African Journal of Biotechnology, 2021

The prospects for using Moringa oleifera leaves extract (MLE) supplemented with different concent... more The prospects for using Moringa oleifera leaves extract (MLE) supplemented with different concentrations of kanwa or sodium bicarbonate (NaHCO 3) as a low-cost alternative growth medium of Spirulina platensis were evaluated in a small-scale outdoor cultivation system. The present study was aimed to evaluate the potential of MLE growth medium enriched with different concentrations (4 or 8 g L-1) of kanwa and NaHCO 3 on growth, chlorophyll content, biochemical characteristics, antioxidant compounds and some physico-chemical factors. Jourdan's standard medium was taken as control. The results showed that the growth parameters such as cell population, biomass dry weight, cell productivity and specific growth rate were positively affected in MLE cultivation medium enriched with kanwa or NaHCO 3 at different concentration levels. The addition of urea, kanwa or NaHCO 3 in MLE cultivation medium at different concentration levels increased significantly (p< 0.05) the protein content, the peroxidase and polyphenol oxidase activity, the conductivity, pH, total dissolved solids and salinity from 20 to 25 days of cultivation whereas a decrease in carbohydrate and phenol content was recorded during all the period of the experimentation. The highest values of growth parameters were notably in MLE medium supplemented with urea and kanwa at 8 g L-1. The MLE medium enriched with urea and kanwa at 8 g L-1 was shown to be an appropriate growth medium that can be used as a lowcost alternative growth medium for commercial cultivation of S. platensis.

Plant Cell, Tissue and Organ Culture, 2008

Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate p... more Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate plants-associated defence markers in plantlets leaves are decisive for development of T. cacao genotypes tolerant to black pods disease (BPD). T. cacao plantlets from manual cross-pollination of ♀SNK64 × ♂UPA143 were analyzed for their susceptibility to BPD using leaf disc test. Subsequently, leaves (healthy, wounded and wound+infected) of selected E9 (tolerant), E13 (moderate susceptible) and E32 (most susceptible) young hybrid genotypes from ♀SNK64 × ♂UPA143 were used for flavones analysis using a HPLC/LC/MS system. Leaf disc test showed 62.5% of the progeny with disease score rates lower than the mean value of both parents. About 79.17% and 20.83% of the progeny were lesser susceptible than the most susceptible parent (UPA143) and the tolerant parent (SNK64) respectively. Total flavones contents were abiotic and biotic stresses-dependant. Under infection, tolerant hybrid genotype (E9) ...

African Journal of Biotechnology, 2017

Black pod disease (BPD) is the major cocoa pathology constraint caused by an Oomycete, Phytophtho... more Black pod disease (BPD) is the major cocoa pathology constraint caused by an Oomycete, Phytophthora megakarya prevailing in African cocoa producing countries. The development of T. cacao planting material tolerant to BPD lies on cross-pollination of adequate parental genotypes which generate offspring with desirable traits. We assessed the susceptibility to BPD of offspring derived from three manual crosses (SNK13xUPA143, T79/501xUPA143 and UPA143xSNK64) using leaf discs test (LDT) which evaluates disease scores of hybrid genotypes. Cysteine involvement in T. cacao defence process against BPD has been studied for the potential use of this sulphur amino acid profile to identify tolerant cocoa hybrid genotypes. LDT displayed variable disease scores patterns. Within a given family, LDT revealed heterogeneity in disease scores. This heterogeneity may have been derived from polygenic character of T. cacao susceptibility to BPD. In SNK13xUPA143 family, 26.13% exhibited disease scores lowe...

Journal of the Cameroon academy of sciences, 2004

Plant protection science, 2017

Minyaka E., Madina Banen C.V., Kusznierewicz B., Doungous O., Haouni S., Hawadak J., Niemenak N.,... more Minyaka E., Madina Banen C.V., Kusznierewicz B., Doungous O., Haouni S., Hawadak J., Niemenak N., Omokolo D.N. (2018): Effect of MgSO4 nutrition on Theobroma cacao susceptibility to Phytophthora megakarya infection. Plant Protect. Sci., 54: 74–82. A new strategy to reduce the severity of black pod disease (BPD) in T. cacao plants using MgSO4 nutrition was investigated. The dynamics of the tolerance to BPD of 18 susceptible T. cacao plantlets coming from the cross (♀SNK64 × ♂UPA14) was monitored during weekly (8 weeks) supply of MgSO4 into the soil. Prior to MgSO4 application, disease scores of the 18 plantlets (in six sets of three plantlets per set) were varying between 3.5 (susceptible) and 5 (highly susceptible). After MgSO4 application, a substantial decrease in disease scores was observed compared to the control. The percentage of disease tolerance gain of plantlets versus MgSO4 supplied (0–2.96 g) presented a quasi-hyperbolic curve with asymptotic line corresponding to 60% (da...

1Department of Plant Biology, Faculty of Science, University of Douala, PO Box 24157 Douala, Came... more 1Department of Plant Biology, Faculty of Science, University of Douala, PO Box 24157 Douala, Cameroon. 2Department of Plant Biology, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé, Cameroon. 3Department of Biochemistry, Faculty of Science, University of Douala, PO Box 24157 Douala, Cameroon. 4Laboratory of Plant Physiology, Department of Biological Sciences, Higher Teacher’s Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon.

Develop T. cacao hybrid genotypes tolerant to P. megakarya is the way out to improve cocoa produc... more Develop T. cacao hybrid genotypes tolerant to P. megakarya is the way out to improve cocoa production and profitability in cocoa producing countries. Hence, the analysis of susceptibility to P. megakarya of the progeny ♀SNK64x♂UPA143 was conducted for the first time. Additionally, cysteine content and myrosinase activity were analyzed in healthy, wounded and wounded_infected leaves in other to bring out the implication of cysteine and myrosinase in T. cacao defense against P. megakarya. The screening for susceptibility to P. megakarya of the progeny ♀SNK64x♂UPA143 has revealed that, more than 58 % of the progeny ♀SNK64x♂UPA143 displayed negative Mid-Parent Heterosis (MPH) and around 79 % were less sensitive to black pod disease than the most sensitive parent UPA143. This set of results indicates that the progeny ♀SNK64x♂UPA143 might be recommended for development of T. cacao hybrid genotypes tolerant or less sensitive to black pod disease. Cysteine content in healthy leaves signific...

Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate p... more Cross-pollination of suitable genotypes and earlier selection of elite offspring using adequate plants-associated defence markers in plantlets leaves are decisive for development of T. cacao genotypes tolerant to black pods disease (BPD). T. cacao plantlets from manual cross-pollination of ♀SNK64 × â™‚UPA143 were analyzed for their susceptibility to BPD using leaf disc test. Subsequently, leaves (healthy, wounded and wound+infected) of selected E9 (tolerant), E13 (moderate susceptible) and E32 (most susceptible) young hybrid genotypes from ♀SNK64 × â™‚UPA143 were used for flavones analysis using a HPLC/LC/MS system. Leaf disc test showed 62.5% of the progeny with disease score rates lower than the mean value of both parents. About 79.17% and 20.83% of the progeny were lesser susceptible than the most susceptible parent (UPA143) and the tolerant parent (SNK64) respectively. Total flavones contents were abiotic and biotic stressesdependant. Under infection, tolerant hybrid genotyp...

Cross-fertilization and somatic embryogenesis stand as potential useful tools for genetic improve... more Cross-fertilization and somatic embryogenesis stand as potential useful tools for genetic improvement and vulgarization of agronomical interesting cocoa planting material for sustainable cocoa culture. Manual cross-fertilization (♀SNK13×♂UPA143) was conducted. ♀SNK13×♂UPA143 derived hybrid genotypes were tested for their susceptibility to black pods disease (BPD). The most tolerant hybrid genotype (KHACa12) was monitored for its precocity, yielding and somatic embryo potential. Peroxidase and polyphenol oxidase activities were evaluated in association to embryogenesis in KHACa12. The cross-fertilization ♀SNK13×♂UPA143 generated around 60% of offprint’s tolerant or less susceptible to BPD. When transferred in experimental farm, KHACa12 produced flowers 18 months after planting. Mature pods from KHACa12 bearded 55±5 seeds/pod. Seventy-five pods were harvested from KHACa12 during the first season. These pods generated 6 kg of fermented-dried cocoa seeds. Somatic embryo responsive revea...

Somatic embryogenesis is a useful tool for Theobroma cacao improvement and propagation. Depending... more Somatic embryogenesis is a useful tool for Theobroma cacao improvement and propagation. Depending on culture medium composition, different morphogenetic structures (including somatic embryo) occur in response to alteration of genes expression patterns and biochemical changes. The effect of SO 4 2 - ion deficiency in culture media on somatic embryogenesis was studied through sequential replacement of MgSO 4 and K 2 SO 4 by MgCl 2 and KCl, respectively, at different steps of somatic embryogenesis. It appears that explants gradually lost their embryogenic competence as the period of exposition to sulphur free medium increases. These results suggest that, sulphur availability and the duration to sulphur exposition might modulate the expression of genes involved in somatic embryo differentiation in T. cacao . Cysteine, glutathione, reducing sugars, cysteine synthase and cysteine desulfurase activities were analysed in different morphogenetic structures obtained in vitro . Cysteine and re...