Studies On Regeneration System In Vitro And The Changes Of Endogenous Hormones Of Welsh Onion(Allium .Fistulosum L.)

An efficient generation system in vitro of welsh onion (Allium .fistulosum.L) was established in this experiment, using the mature embryos as explants, and the endogenous hormones changes during regeneration was studied.The different organs of welsh onion-immature leaves, roots, floral buds and mature embryos were used as explants to induce callus. It was indicated that the mature embryo was the best, with high and stable induction rate; the floral bud ranked the second whose growth stage was a key factor to tissue culture; immature leave and root were difficult to induced callus.The mature embryo could induce callus efficiently in the medium supplemented with 2,4-D 1.0-2.0 mg.l-1 + 6-BA 2.0-4.0 mg.l-1. It was better to adopt low concentrations of 2,4-D and 6-BA if considering the differentiation and vitrification of adventitious shoots. The best hormone combination for callus induction was 2,4-D 1.0 mg.l-1 + 6-BA 2.0 mg.l-1, which was also the best for callus multiplication. Differentiation was induced from the callus prematurely if the concentration of 2,4-D was decreased or NAA was used instead of 2,4-D in the earlier stage. The concentration of 2,4-D should be decreased timely to keep the differentiation ability of callus. The best hormone combination for differentiation was NAA0.5 mg.l-1+6-BA1.0 mg.l-1. Although the differentiation ration could be increased with the increasing of the concentration of 6-BA, serious vitrification was investigated. The adventitious shoots should be transferred to MS0 on time to reduce vitrification. Substrate (vermiculite + peat moss=1:1) was the best one for the growth of welsh onion regenerative plantlets, probably because that its property of ventilation and retaining water was good. The somatic embryos were induced from the callus, which were induced for 30d, then were subcultured on the medium supplemented with 2,4-D 1.0 mg.l-1 + 6-BA 2.0 mg.l-1, followed by on 2,4-D 0.5mg.l-1 + 6-BA2.0mg.l-1, each for 30d respectively. Somatic embryos were obtained from such embryogenic callus after transferred to medium with NAA0.25 mg.l-1+6-BA1.0 mg.l-1.The buds and callus of welsh onion had higher resistance to Kan , for some of them survived, callus even could grow slowly when the concentration of Kan was 200.0 mgl-1.This was similar to some other monocotyledon. Relatively , they were more sensitive to G418, for they were killed completely when the concentration of G418>= 30.0 mg.l-1. So G418 is fit to Chinese onion transformation as selective reagentantibiotic, when using nptâ…¡as report gene.It was indicated, from the endogenous hormone change in the course of mature embryos of welsh onion regeneration, that auxin had phase effect: it affected actively in the start-up stage of callus inducing with its high concentration; and affected negatively in the start-up period of differentiation with its low concentration. Abscisic acid had probably negative effect for callus induction. The amount of gibberellin was higher in the course of differentiation than multiplication period, which indicated its effect to facilitate differentiation. Cytokinin was probably the main factor resulting in vitrification,because its content increased rapidly in the period of adventitious shoots vitrified and decreased in the period of vitrification fading away.