In vitro adventitious shoot formation on petioles of commercial cultivars of delphinium

Culture conditions of plant growth regulators were examined for promoting efficient plant regeneration from petiole explants of commercial cultivars of delphinium. The optimal combination of a cytokinin and an auxin was determined using petiole explants of delphinium cv. Blue Springs. Concentrations of individual cytokinins for the optimal regeneration of shoots were 10 mg l(-1) for 6-benzylaminopurine, 1 mg l(-1) for N-phenyl-N'-1,2,3-thiadiazol-5-yl urea and 5-10 mg l(-1) for zeatin, in combination with 2,4-dichlorophenoxyacetic acid at 1 mg l(-1). We applied these optimized conditions for regeneration of adventitious shoots to petiole explants of 18 other commercial cultivars. Adventitious shoots regenerated from 14 cultivars out of the 19 ones tested at frequencies of 2-53%. Shoots of cv. Blue Springs that had regenerated in vitro rooted in a hormone-free medium and finally were transferred to soil. (C) 2001 Elsevier Science B.V. All rights reserved.