Differential In vitro Direct Shoot Regeneration Responses in Embryo Axis and Shoot Tip Explants of Faba Bean

Abstract

An efficient plant regeneration procedure using embryo axis and shoot tip explants was developed in faba bean (Vicia faba L.). Embryo axes and shoot tips were cultured on MS medium (Murashige and Skoog 1962) supplemented with benzyladenine (BA) and thidiazuron (TDZ). Differential regeneration efficiency was observed due to factors including growth regulator combinations in the medium, explants, basal media and lines used. Explants cultured on medium with TDZ in combination with BA produced a higher number of shoots compared with either cytokinin alone. The embryo axes promoted the formation of more adventitious shoots than shoot tips. The frequency of multiple shoot formation varied among the lines tested. Line 740 cultured on MS medium containing TDZ in combination with BA (2.0 mgl^-1 each) gave the highest number of shoots per explant (10.2 and 7.7) from both embryo axes and shoot tips, respectively. Explants cultured on MS or MSB (MS salts+B5 vitamins) produced the highest number of shoots. The efficiency of TDZ combined with BA for multiple shoot induction was not improved when 0.25-1.00 mgl^-1 of naphthaleneacetic acid (NAA) was added. Regenerated shoots were rooted on half-strength MS basal medium lacking growth regulators or supplemented with either NAA, IBA or IAA (0.25-1.0 mgl^-1) prior to transfer to greenhouse conditions. We developed a rapid, reliable, high-frequency method for producing multiple shoots from faba bean shoot tip and embryo axis explants.