Somatic embryogenesis in Arachis hypogaea: revisited

Direct somatic embryogenesis is an efficient method of plant regeneration, allowing rapid multiplication of plants in a short period. Six experiments were conducted to study the influence of auxin level on somatic embryogenes is and to optimise the concentration of auxins. Immature embryo axis was th e ideal explant and 20-40 mg L-1 of 2,4-dichlorophenoxyacetic acid was the best concentration range for obtaining the maximum number of free somatic e mbryos. Significant differences were observed between the genotypes for ind uction and the number of somatic embryos per explant. The cv. Girnar 1 prod uced the maximum number of somatic embryos per explant, the number of secon dary somatic embryos ranging from 1.5 to 9.4. The overall germination of so matic embryos was 42.8%, and 65% of the plantlets transferred to the field survived. The development of somatic embryos was from the apical region of the embryo axes without undergoing dedifferentiation. The initial cell divi ded to form a tier of four cells and subsequent anticlinal and periclinal d ivision resulted in the development of globular somatic embryos with small suspensors, followed by heart-shaped, torpedo-shaped and 'cotyledonary' sta ges.