Influence of plant growth regulators on somatic embryogenesis in Niger (Guizotia abyssinica Cass.): an edible oilseed crop

An improved protocol of direct somatic embryogenesis (SE) and shoot regeneration was developed, for the first-time, using leaf explants from in vitro raised shoots of Guizotia abyssinica. We have studied the effect of cytokinins and auxins viz. 6-benzylaminopurine (BAP), kinetin, indole-3-acetic acid (IAA), α-naphthaleneacetic acid (NAA) and 2,4-dichloro phenoxyacetic acid (2,4-D), individually and in combination for their effectiveness to induce direct SE and shoot regeneration. MS medium containing 1.0 mg L−1 BAP together with 0.5 mg L−1 IAA showed maximum frequency of explants responding for SE and number of somatic embryos per explant. Somatic embryos germinated within 2 weeks of transfer to MS medium supplemented with 0.25 mg L−1 BAP whereas plantlet development with rooting was observed on MS containing 0.25 mg L−1 NAA in the next 2 weeks. This regeneration system increased the efficiency of explants responding to SE by 100%, reduced the time taken for SE by 4–6 weeks, minimized the influence of environmental factors and HgCl2 on response of explant, and also chances of appearance of developmental aberrations due to exposure to 2,4-D and callus intervention. Over 90% of regenerated plantlets survived following hardening and transfer to a mixture of sand and soil. Morphological, cytological, and flow cytometric analysis suggested that the plantlets were phenotypically and genetically similar. The method provides an efficient tissue culture system for rapid propagation and for genetic manipulation studies.