Sweetpotato plant regeneration via an improved somatic embryogenesis protocol

Genetic transformation holds considerable promise for sweetpotato enhancement, but is limited by the low regeneration efficiency of transformed cells. Somatic embryogenesis is the most efficient method for regenerating genetically transformed sweetpotato plants, but is still limited by low efficiency and strong genotype dependency. In this study, based on a review of previous work, various growth regulators and gelling agents were assessed for an optimized three-stage protocol. Lateral meristems of sweetpotato cultivars ‘Jonathan’ and ‘Jewel’ were used to investigate: (i) the influence of the auxins 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) on the induction of sweetpotato somatic embryogenesis, (ii) the effect of the abscisic acid (ABA) and gibberellic acid (GA₃) on the development and maturation of somatic embryos, (iii) the effect of GA₃ on development of mature embryos into plantlets, and (iv) the influence of two gelling agents (agar and Gelrite) on different embryogenic phases during all stages of the protocol. Among the treatments evaluated, best results were obtained when growing the explants on Murashige and Skoog (MS) medium with 1.3 mg/l 2,4,5-T (in the dark) during the first stage, transferring the calli to media with 1 mg/l ABA at the second stage and then cultivating them on 0.424 mg/l GA₃ for plant development. However, no significant differences were found between gelling agents.