Effect of plant growth regulators on in vitro regeneration of Onion (Allium cepa L. var. aggregatum Don.)

In vitro plant regeneration was achieved in Onion (Allium cepa L. var.aggregatum Don.) cv.CO (On.) 5. Basal plate explants were cultured on MS medium fortified with different concentrations of benzyl amino purine (BAP; 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg/l), naphthalene acetic acid (NAA; 0.2, 04, 0.6, 0.8, 1.0, 1.2 and 1.4 mg/l) either alone or in combination for multiple shoot induction.Presterilization of the basal plate of onion in 0.5% solution of bavistin, followed by treatment with 0.1% mercuric chloride for 10 min produced the highest rate of survival of explants.Basal plate explants produced a greater number of shoots when cultured with MS medium containing different combinations of BAP and NAA.The highest rate of multiple shoot induction (12/explant) was observed under basal plate explants cultured in MS medium with 3.0 mg/l of BAP and 0.4 mg/l of NAA.Increasing BAP concentration up to 3.0 mg/l favored shoot initiation and multiplication, while shoot initiation and multiplication were decreased in MS medium containing BAP (4 mg/l).Shoots were allowed to root in vitro on MS medium containing IBA (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg/l) or NAA (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg/l).IBA was found to be superior to NAA for induction of root development in vitro in basal plate explants.Rooting of in vitro raised shoots was best induced on MS supplemented with 1 mg/l indole-3-butyric acid (IBA) with 10 roots per shoot and 3.10 cm root length.The rooted shoots were acclimatized with a success rate of 85%.