Abstract
Somatic embryogenesis (SE) and organogenesis are crucial in the development of disease free plants and genetic engineering. An investigation was conducted on the ability of treatments containing a combination of 2,4-D and Kinetin to induce either SE or organogenesis from cultured sweet potato cv Brondal leaves. Ten treatments were evaluated and each treatment had an exclusive combination of 2,4-D (at 0.05, 0.1, 0.2, 0.5 or 1 mg/L) to kinetin (at either 0.1 or 0.5 mg/L). Callus initiation occurred earlier in treatments containing higher hormonal concentrations. The 2,4-D to Kinetin ratio had a highly significant ( p = 0.001 ) effect on callus growth and proliferation. Increasing 2,4-D to Kinetin ratio promoted profuse explant callusing while increasing Kinetin to 2,4-D ratio suppressed callusing but encouraged organogenesis, in particular shoot production (treatment containing 0.05 mg/L 2,4-D and 0.5 mg/L Kinetin). Embryogenic calli were formed seven weeks after leaf culture in the treatment containing 0.5 mg/L 2,4-D and 0.1 mg/L Kinetin. The embryogenic calli that developed from this treatment emerged from previously nonembryogenic calli. Plantlets produced via the SE pathway proved to be weak and unviable and died within four weeks of germination. In contrast, plantlets produced under organogenesis were strong, grew vigorously, and could be subcultured several times. This disparity may be accounted for by the fact that the cv Brondal embryos that developed under SE were not exposed to an embryo maturation staged before plantlet germination was initiated. The maturation stage would have assisted embryos to reach physiological maturity and a desired level of desiccation, both being critical elements in embryo to plantlet conversion. In this experiment, cv Brondal regeneration from leaf explants was successfully achieved via organogenesis using 0.05 mg/L 2,4-D and 0.5 mg/L Kinetin, and tentative steps towards development of SE based regeneration protocol were established using 0.5 mg/L 2,4-D and 0.1 mg/L Kinetin.
Highlights
Sweet potato (Ipomoea batatas L.) is ranked as the seventh most important crop after wheat, rice, maize, potato, barley, and cassava [1]. e tuber bearing plant is vegetatively propagated and is mainly cultivated for its storage roots [2]
Since the early 1980s sweet potato regeneration has been reported for several cultivars and has been proceeded via somatic embryogenesis (SE) or organogenesis pathways [11, 12]. e SE pathway is generally accepted to be the better route for plant regeneration since by its very nature, it tends to lead to the production of a greater number of regenerates compared to the organogenesis pathway [13, 14]
Zimbabwe’s highest yielding sweet potato cv Brondal has been regenerated using the organogenesis pathway [19], it would be of paramount importance to be able to regenerate this cultivar via SE as this would facilitate the improvement of the crop via genetic engineering. e objective of this study is to develop a somatic embryogenesis regeneration protocol for Zimbabwean sweet potato cv Brondal using leaves as explants
Summary
Sweet potato (Ipomoea batatas L.) is ranked as the seventh most important crop after wheat, rice, maize, potato, barley, and cassava [1]. e tuber bearing plant is vegetatively propagated and is mainly cultivated for its storage roots [2]. Smallholder farmers in Zimbabwe depend on the sweet potato crop to feed their families and to generate income through sell of tubers and vines [6]. E importance of plant tissue culture techniques in sweet potato propagation cannot be underscored. Tissue culture has been used as a tool to preserve germplasm, in the rapid production of disease free plant propagules [7, 8] and Advances in Agriculture regeneration protocols have been used to aid in the genetic improvement of sweet potato [9, 10]. E SE pathway is generally accepted to be the better route for plant regeneration since by its very nature, it tends to lead to the production of a greater number of regenerates compared to the organogenesis pathway [13, 14]. Organogenesis has an advantage over SE as the plantlets regenerated via organogenesis grow faster and tend be true to type [17, 18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
