Efficient plant regeneration from suspension-cultured cells of tall bearded Iris

A protocol was developed for efficient plant regeneration of Iris germanica L. 'Skating Party' from suspension cultures. Suspension cultures were main tained in Murashige and Skoog (MS) basal medium (pH 5.9) supplemented with 290 mg.L-1 proline, 50 g.L-1 sucrose, 5.0 mu M 2,4-D, and 0.5 mu M Kin. Sus pension-cultured cells were transferred to a shoot induction medium (MS bas al medium supplemented with 10 mg.L-1 pantothenic acid, 4.5 mg.L-1 nicotini c acid, 1.9 mg.L-1 thiamine, 250 mg.L-1 casein hydrolysate, 250 mg.L-1 prol ine, 50 g.L-1 sucrose, 2.0 g.L-1 Phytagel, 0.5 mu M NAA, and 12.5 mu M Kin) . Cell clusters that proliferated on this medium differentiated and develop ed shoots and plantlets in about 5 weeks. Regeneration apparently occurred via both somatic embryogenesis and shoot organogenesis. A series of experim ents was conducted to optimize conditions during suspension culture to maxi mize subsequent plant regeneration. Parameters included 2,4-D and Kin conce ntrations, the subculture interval, and the size of cell clusters. The high est regeneration rate was achieved with cell clusters less than or equal to 280 mu m in diameter, derived from suspension cultures grown for 6 weeks w ithout subculturing in liquid medium containing 5 mu M 2,4-D and 0.5 mu M K in. Up to 4000 plantlets with normal vegetative growth and morphology could be generated from 1 g of suspension-cultured cells in about 3-4 months, Ch emical names used: 2,4-dichlorophenoxyacetic acid (2,4-D); kinetin (Kin); 1 -naphthaleneacetic acid (NAA).