666 (PS 4) THIDIAZURON-MEDIATED INDUCTION OF ADVENTITIOUS SHOOTS IN SWEETPOTATO

Abstract

An efficient two stage protocal has been developed for inducing adventitious shoots from the in vitro - derived petiole pieces of sweetpotato. Petiole sections (0.5 -1 cm) were taken from apical portions of the sweetpotato cultivar USDA PI 318846-3. Explants were placed horizontally on the first stage media (Murashige and Skoog basal medium + 2,4 -D, 0.2 mg/L) for 2 to 4 days, then transferred to the second stage and kept vertically with the base of the petiole inside the medium. During the second stage, the MS medium was supplemented with various levels (0.0 mg/L to 4 mg/ L) of thidiazuron (TDZ). High and rapid shoot regeneration was observed on TDZ, 0.2 mg/L (36% of explants developing shoots in 15 days), resulting in a maximum of 80% regeneration frequency by 30 days of Incubation. Increasing concentrations of TDZ (> 0.4 mg/L) lowered the shoot and root regeneration. Although the shoots grew slightly slow on the MS + TDZ (0.2 mg/L) medium, they rooted normally and grew vigorously when transferred to a hormone-free medium. Whole plants were acclimatized by culturing in sterile soil and then grown in the green house. This protocol may be suitable for genetic transformation studies using Agrobacterium vector and particle bombardment approaches.