In Vitro Cloning of Antirrhinum Majus – An Important Ornamental Plant

Abstract

ABSTRACT Antirrhinum majus is an attractive herbaceous plant cultivated as ornamentals for its aesthetic view. Shoot tips, nodal segments, stem and leaves were excised from field grown mature plant and transferred to variously supplemented Murashige and Skoog’s medium with various hormones for multiple shoot proliferation, callus induction and de novo adventitious root and shoot formation directly from the explant or indirectly from the callus raised from the explants. Antirrhinum majus also exhibited multiple shoot proliferation from nodal segments. Out of all the cytokinins tested, multiple shoot formation was observed on MS medium supplemented with BAP (4 mg/l) resulting in the formation of 12-14 shoots after 6 weeks of culturing. Acceptable multiplication rates were obtained from shoot tips when transferred to MS medium supplemented with Kn(2 mg/ml) where a maximum of 15-16 shoots were formed. MS medium supplemented with BAP (4 mg/l) also promoted multiple shoot proliferation leading to the formation of 12-14 shoots after 6 weeks. A noticeable feature observed was the induction of roots along with the multiple shoot proliferation. Once the clusters of shoots were formed, small clumps of 2-3 shoots were excised and transferred onto fresh multiplication medium where they exhibited continuous shoot proliferation. The regenerated shoots thus formed were excised and transferred to different root inducing media to form complete plantlets. Among the various growth regulators tested, NAA (2 mg/l) showed the best results where roots appeared after 2 weeks which elongated further forming numerous roots after 4-5 weeks. The plant exhibited good degree of propensity for de novo adventitious root formation directly from the stem and leaf segments. Direct root regeneration from the stem segment was observed on different concentrations of NAA (0.5-2 mg/l) where as de novo root formation from leaf segment was observed only from NAA (4mg/l). The roots were thin, white, long and bore profuse root hairs. The present plant material did not exhibited de novo adventitious shoot formation in any of the media tried. Callus induction from stem and leaf explants was observed on MS medium supplemented with 2,4-D in combination with cytokinins such as BAP and Kn. Auxin such as NAA used in combination with BAP and Kn also promoted callus formation. The calli obtained from leaf and stem segments was hard, compact and whitish green in color.The callus was heterogenous in nature being composed of ovoid, oblong, semicircular cells or those with aberrant shapes. Histogenetic differentiation in the form of tracheids was observed. Tracheids occurred singly or in groups and possessed reticulate thickenings on their walls. No oraganogenetic differentiation could be effected from the calli on the various media tried.

Keywords: Antirrhinum majus, de novo root and shoot formation, Murashige and Skoog’s medium, multiple shoot proliferation, callus induction, , organogenetic differentiation