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

Culture conditions of plant growth regulators were examined for promoting e fficient plant regeneration from petiole explants of commercial cultivars o f delphinium. The optimal combination of a cytokinin and an auxin was deter mined 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-dichloroph enoxyacetic acid at 1 mg l(-1). We applied these optimized conditions for r egeneration of adventitious shoots to petiole explants of 18 other commerci al 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 tran sferred to soil. (C) 2001 Elsevier Science B.V. All rights reserved.