Shoot Regeneration in Vitro from Diverse Genotypes of Sweetpotato and Multiple Shoot Production per Explant

Abstract

Studies were conducted to improve adventitious shoot regeneration in sweetpotato [Ipomoea batatas (L.) Lam.], specifically to extend the protocol to many genotypes and to elicit production of multiple shoots per explant. The use of a two-stage procedure where excised petioles were incubated on Murashige and Skoog (MS) (1962) medium with 2,4-D (0.2 mg·liter–1) for 3 days and transferred to a second medium containing MS salts with thidiazuron and 2iP (0.05 mg·liter–1 each) resulted in shoot regeneration from eight of 13 genotypes tested, including elite sweetpotato cultivars such as `Jewel' and `Rojoblanco'. PI 318846-3 was the most regenerable genotype, with up to 77% of explants producing one to three shoots per explant. The orientation of the petiole on the nutrient medium was critical; those placed vertically inverted developed multiple shoots. Wounding explants through epidermal peeling with normal horizontal orientation of the explants during incubation also resulted in multiple shoot production (about three shoots per explant). Interference with auxin transport due to explant inversion or wounding may have stimulated increased shoot induction. Chemical names used: 2,4 dichlorophenoxyacetic acid (2,4-D); N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (thidiazuron); N6-(2-isopentenyl) adenine (2iP).