Comparison of first stages of somatic embryogenesis in Baillonella toxisperma and Vitellaria paradoxa

In order to initiate the in vitro propagation of Baillonella toxisperma and Vitellaria paradoxa, a comparative study of somatic embryogenesis was studied on these two Sapotaceae using leaf fragment from plants under production. A culture medium of Murashige and Skoog half strength (MS/2) supplemented with 0.6% agar and 4.5% sucrose was used as the basic medium. 0.5 mg times l super(-1) of 6-benzylaminopurine (BAP) and 0.5 to 5 mg times l super(-1) of 2.4-dichlorophenoxyacetic acid (2.4-D) were added to the basic medium to study the process of callogenesis and the formation of the somatic embryo on the callus. The BAP/2.4-D combination significantly affected callogenesis in both species. During 28 days of culture, the most reactive combinations are 0.5/0.5 in B. toxisperma which allowed 75.2% of the explants to form callus, and 0.5/3 in V. paradoxa which permitted to obtain up to 87.3% callogenesis. At 3 mg times l super(-1), 2.4-D permitted the differentiation of somatic embryos in 92.7% of callus in B. toxisperma with an average of 38 embryos per callus. On the contrary in V. paradoxa, the most reaction is observed with the combination of 0.5/2 BAP/2.4-D which permitted to obtain 62.1% of embryonic callus in 97 days of culture with an average of 27 embryos per callus. The histological study of embryonic callus showed that the development of the differentiated somatic embryos occurs through the same stages in both species; notably the nodular stage, the division of nodular cells stage and the bipolar embryos stage, thus the respective percentages obtained are 77.2% and 66.8% in B. toxisperma and V. paradoxa. Though this work opens probably new way of propagation of these two species, the transformation of the bipolar embryos into viable plants remains important phase to study.Original Abstract: En vue d'initier la propagation in vitro de Baillonella toxisperma et Vitellaria paradoxa, l'embryogenese somatique a ete etudiee de facon comparative chez ces deux Sapotacees a partir des fragments de feuille preleves sur des plantes en production. Le milieu de Murashige et Skoog, dilue de moitie (MS/2) et additionne de 0,6% d'agar et de 4,5 % de saccharose, a ete utilise comme milieu de base. La 6-benzylaminopurine (BAP) (0,5 mg times l super(-1)) et l'acide 2,4-dichlorophenoxyacetique (2,4-D) (0,5 a 5 mg times l super(-1)) ont ete ajoutes a ce milieu de base pour etudier la callogenese et la formation des embryons somatiques sur les cals. Chez les deux especes, l