L'étiolement est un facteur d'induction de l'embryogenèse somatique au cours de la callogenèse chez deux variétés récalcitrantes de cotonnier (Gossypium hirsutum L.) cultivées en C te d'Ivoire

Darkness etiolement is a favorable pre-treatment to induce somatic embryogenesis from hypocotyls of cotton (Gossypium hirsutum L.). In vitro tissue culture of two varieties of cotton, ISA 2 0 5 N and ISA G L 7, (Gossypium hirsutum L . ) , cultivated in C te d Ivoire, was established from hypocotyls fragments. These fragments were excised from etiolated and non etiolated seedlings (absence or presence of chlorophyll). The objective of the study was to induce somatic embryogenesis from these genetically non embryogenic varieties. The non etiolated hypocotyls of both varieties showed a significantly higher percentage of callus induction compared to the etiolated ones. However, cells proliferation from etiolated hypocotyls were higher only for variety ISA 205 N. Histological study of callus indicated that embryogenic cells or embryos formation depend on the origin of explants used in culture. With callus derived from etiolated explants, embryogenesis started earlier and embryos at the globular and heart-shape stage were observed after four months. With callus generated by non etiolated explants, cellular division was high with no embryo formation. From these results, it appears that variety ISA 205 N is more embryogenic than ISA GL 7. Additionally, it was shown that the darkness pre-treatment of the cultured explants would be a good condition to induce somatic embryogenesis of cotton.