Objective: In cocoa tree (Theobroma cacao L.), some elite genotypes have shown, in standard study conditions, an absence or a very weak response to induction of somatic embryos. This is the case of the original C8 genotype Trinidad. This study aims to improve the production of somatic embryos in this genotype Methodology and results: To do this, staminodes and petals excised from immature buds of genotypes C1, C8 and C14 were used. Genotypes C1 and C14 are embryogenic under standard conditions. These floral explants were cultured on induction media differing by the type and concentration of auxins. Callus induction obtained in the three studied genotypes ranged from 80% to 90% with the petal explants and from 70% to 80% with the staminodes regardless of the type and concentration of auxins. Transfer of callogenic explants to DKW (Driver & Kuniyuki, 1984) medium supplemented with sucrose and glucose allowed the induction of somatic embryos at mean rates varying from 5% to 20% after only 84 days with petal explants and media supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4, 5-trichlorophenoxyacetic acid (2,4,5-T). No induction of somatic embryos was observed on the control medium with the C1, C8 and C14 genotypes. The C1 genotype induced somatic embryos in the presence of all concentrations of auxins. The highest rate of embryogenic callus and somatic embryo induction was obtained with 18 μM of 2, 4, 5-T in all C1 genotypes (39.29 ± 0.28; 17.98 ± 0.10), C8 (36.29% ± 0.26 and 15.01 ± 0.07) and C14 (33.92% ± 0.26 and 14.50 ± 0.16). The 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T). at 18 μM is the most appropriate auxin to remove recalcitrance in cocoa genotype C8. The use of higher 18 μM concentrations of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T). and its application to other recalcitrant genotypes could confirm its beneficial effect on the removal of recalcitrance to somatic embryogenesis in cocoa. Conclusion and application of results: 18 μM concentration of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) gave the best percentage of embryogenic explants and the highest average number of embryos in the three genotypes tested. Therefore, this protocol using 18 μM of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) could be used to overcome recalcitrance to somatic embryogenesis in cocoa.
RESUMEAprès 15 années de pollinisation manuelle, la fertilité femelle des clones cultivés wickham de Hevea brasiliensis a été évaluée en Côte d'Ivoire, à partir de 3 estimateurs tels que : les taux de nouaison, d'abscission des fruits et de succès à la pollinisation. La structuration de cette fertilité, par rapport aux 3 estimateurs, a été étudiée chez 5 clones cultivés wickham, à l'aide de l'analyse factorielle discriminante. Mots-clés :Hevea brasiliensis, nouaison, abscission, fruits, pollinisation. ABSTRACT FEMALE FERTILITY OF FIVE RUBBER TREE CLONES (Hevea brasiliensis MUELL ARG) IN CÔTE D'IVOIREAfter 15 years of manual pollination in Côte d'Ivoire, female fertility of Hevea brasiliensis rubber tree clones was assessed from 3 estimators of fertility, which were the aborted seed, was studied in 5 wickham clones, using a discriminate factor analysis. The PB5/51, PB260 and PB235 clones, which were good seeders, had high initial and final fruit set average rates (11.23 to 15.17 % and 7.09 to 9.13 %), with the highest average rates of aborted seeds (31.72 to 55.91 %). These were, either lower, or higher (18.86 to 41.84 %) for the GT1 and AVROS2037 clones, which were found to be bad seeders. Overall, the study showed a better understanding of the low fertility of the Hevea brasiliensis rubber tree through the identification of good (PB5/ 51, PB 260, PB 235) and bad seeders (GT 1, AVROS 2037).
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