Abstract
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 revealed that 71.041 ± 7.91% and 50.64 ± 9.48% staminodes and petals derived explants, respectively produced direct and indirect somatic embryos. Morphologically, the somatic embryos obtained were similar to zygotic embryos from the same hybrid genotype (KHACa12). Peroxidase and polyphenol oxidase activities profiles in zygotic and somatic embryos increase during the first stages of embryogenesis, then decrease when cotyledons developed. These results might indicate that, ♀SNK13×♂UPA143 could be used to develop cocoa (Theobroma cacao L.) hybrid genotypes tolerant or less susceptible to BPD. KHACa12 is an agronomic interesting hybrid genotype that could be produced in large scale and vulgarized using somatic embryogenesis process. The initiation and development of somatic embryo in KHACa12 can be monitored and modulated biochemically through peroxidase and polyphenol oxidase activities profiles. Key words: Breeding, tissue culture, somatic, explants, hybrid.
Highlights
The chocolate and cocoa butter tree (Theobroma cacao L.) is a perennial tropical crop widely cultivated in Africa, Asia and America
Manual cross-fertilization (♀SNK13×♂UPA143) was conducted. ♀SNK13×♂UPA143 derived hybrid genotypes were tested for their susceptibility to black pods disease (BPD)
KHACa12 is an agronomic interesting hybrid genotype that could be produced in large scale and vulgarized using somatic embryogenesis process
Summary
The chocolate and cocoa butter tree (Theobroma cacao L.) is a perennial tropical crop widely cultivated in Africa, Asia and America. Cocoa production is challenged with reliable planting material crisis. Used planting material are low yielding and highly sensitive to disease (Phytophthora megakary specially). Improved planting material is not available or accessible to farmers. In many African cocoa producing countries, 25% of cocoa farms are made of improved planting material. Most cocoa farms are old and need to be renewed with elite cocoa genotypes. Developed and vulgarized elite cocoa genotypes are the ways out for sustainable cocoa production and profitability. Tremendous efforts have been put on cross-fertilization of targets T. cacao clones in order to provide farmers with elite cocoa genotypes. Since the parental clones are always heterozygote for these characters, the offprints from cross-fertilization of targets T. cacao clones are highly heterozygote. The proportion of hybrid genotypes for the character such as tolerance P. megakarya did not exceed 1/3 (Tahi et al, 2000; Nyasse et al, 2003)
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