A protocol of plant regeneration through direct somatic embryogenesis was established for the first time on Vinca herbacea using immature seed explants. Frequency of embryogenesis was significantly influenced by size of the seeds and growth regulators supplemented to the medium. Seeds isolated from the immature fruits between 15 and 20 days after flowering were superior in the induction of somatic embryos. Only 35% of seeds induced somatic embryos. Somatic embryos developed best on N2 medium with 0.5 mg l−1 2,4-D and 0.5mg l−1 Kin. An increase in competence for somatic embryogenesis was found with the cotyledons, while the hypocotyls part completely lost their competence. The minor seeds never initiated somatic embryo, even after 2 months of culture. Somatic embryo formation principally occurred with the major seeds. Maturation embryos developed into plantlets at a frequency of 100% when planted in free MS medium for a further 5 - 6 week period. After 5 or 6 weeks, plantlets developed in small plants. The growth rates, genotype and morphological characteristics of plantlets were different but 55% of the embryos have normal shape and 45% were abnormal.
Key words: Embryo formation, growth regulators, plantlet.
2,4-D, 2,4-Dichlorophenoxy acetic acid; Kin, kinetin; MS, Murashige and Skoog; 2,4,5-T, 2,4,5-threechlorophenoxy acetic acid; IAA, indole acetic acid; IBA, indole buteric acid.
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