In vitro regeneration from seedling organs of Brassica oleracea var. italica Plenck cv. Green Comet I. Effect of plant growth regulators

The calabrese cultivar Brassica oleracea var. italica cv. Green Comet was used in a study of the effects of exogenous hormones on the growth and differentiation of seedling organs in vitro. Four types of explants were tested: hypocotyl segments, root segments, primary leaf discs and cotyledon discs. These explants were incubated on media containing factorial combinations of BAP x IBA, BAP x NAA, KN x IBA and KN x NAA(all at 0, 0.1, 1.0 and 10.0mgl-1). Hypocotyls were the most regenerative explants; shoot production was favoured by cytokinin:auxin ratios greater than one and was decreased by IBA at 10 mg I"1 when callus was produced. Shoot formation from root explants occurred either in the absence of hormones or with low concentrations; no shoot was produced when any hormone was present at lOmgl-1. In contrast, shoot production from primary leaf discs was favoured by high concentrations of both auxin and cytokinin with the combination of BAP and IBA the most effective. Shoot production from cotyledon discs was sporadic with no consistent response on any auxin/cytokinin combination. After further experiments on the optimization of hormone concentration, the following combinations were chosen as allowing reliable regeneration:0.1 mg l-1 BAP+0.lmgl-1 IBA for hypocotyl segments, 0.075 mg l-1 K.N + 0.025 mgl-1 IBA for root segments, and 5.0 mg l-1 BAP+5.0 mg l-1 IBA for leaf discs