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

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.

Use of mineral salts to remove recalcitrance to somatic embryogenesis of improved genotypes of cacao (Theobrama cacao L.)

“…This shows that the lowest concentrations are sometimes insufficient to overcome the recalcitrant ; however, when they are too high they cause toxicity regardless of the compound. Inhibition of somatic embryo production of T. cacao would be due, in addition to the insufficiency or toxicity of certain compounds used, to a strong secretion of ethylene and polyphenols by the explants of certain genotypes according to Fang et al (2014) and Minyaka et al (2017).…”

“…The work of Alemanno et al (1996) and Boutchouang et al (2016) conducted on cacao flowers showed that they would synthesize a significant quantity of phenolic compounds. Indeed, these compounds intervene in the defense of plants (Kouassi et al, 2017a;Minyaka et al, 2017). When the plant is subjected to mechanical injury, simple phenols are synthesized and the peroxidase activity characteristic of the lignifying tissues is stimulated.…”

Effect of Glomus intraradices in improving the tolerance of a hybrid family of Theobroma cacao L. against Phytophthora megakarya

“…showing that tolerance to brown pod rot was under genetic control and could be improved; explaining that the presence of susceptible and resistant genotypes in the same hybrid family confirms an excellent combination of parental genes (Cilas et al, 2004;Manga et al, 2016;Effa et al, 2017;Minyaka et al, 2017;Ondobo et al, 2017). and Ficup 34 showed necrotic surfaces greater than 0.5 cm 2 and more, none of the hybrid genotypes reached a necrosis area of 1 cm 2 (Table 2).…”