Clonal Propagation of Nasturtium-an Ornamental Plant Through Tissue Culture

Abstract

2 The present investigation was carried out on a herbaceous angiosperm namely Tropaeolum majus belonging to family Tropaeolaceae. It is commonly known as “Garden Nasturtium” and is grown as an ornamental in the gardens. Different vegetative parts like root stem, leaves, and shoot apices were excised from both the in vivo and in vitro raised plants and thereafter planted on Murashige and Skoog’s medium supplemented with various growth adjuvants for callus induction, organogenesis and multiple shoot formation. Multiple shoot proliferation was effected from shoot apices on MS medium supplemented with various growth adjuvants in different combinations. Multiple shoot formation occurred on MS supplemented with BAP (0.5 – 4 ppm) either alone or in combination with NAA (0.5 ppm). Best results, however, were obtained on MS + BAP (4 ppm) where 25 – 35 shoots regenerated from a single shoot apex. It was also observed that initial treatment with BAP (2 – 4 ppm) for 2 - 3 weeks followed by transfer to lower concentration of BAP (0.01 - 0.1 ppm) or simple MS medium proved most effective in terms of new shoot production and shoot growth rate. The shoots thus formed were excised and transferred to different root inducing media. Roots, stem and leaves were planted on variously supplemented MS medium for organ regeneration and callus induction. Nasturtium exhibited a high propensity of rooting from all the vegetative parts of the plant. Prolific root regeneration directly from these explants was observed on MS supplemented with NAA (1 - 4 ppm) with or without Kinetin. Best results, however, were obtained on MS + NAA (4 ppm) only. Direct Shoot regeneration was effected from stem explants of both in vivo and in vitro raised plants. Shoot regeneration directly from stem explants was observed on simple MS medium, MS + 2, 4-D (2 ppm) + CM 15 %, and MS + 2, 4-D (2 ppm) + Kinetin (1 ppm) + CM 15 %. Best results were however, obtained on simple MS medium, where 15 – 20 shoots regenerated from the stem explant. The regenerated shoots were transferred to MS medium having IAA or IBA for adventitious root initiation. After shoot and root development, attempts were made to establish regenerated plantlets into soil through a series of hardening stages. Callus induction was effected from petiole and stem segments of both in vivo and in vitro reared plants. Synergistic action of 2, 4-D (2 ppm), and CH (2g/l) was demonstrated for the initiation and good growth of Callus .Calli obtained from petiole and stem explants on MS + 2,4-D (2 ppm) + CH (2g/l) was yellowish, solid and slow growing. Cell types studied in various calli showed their heterogeneous nature with wide variations in the size and shapes of cells. Histogenetic differentiation in the form of tracheids was observed in all the calli. Tracheids occurred singly or in groups and possessed scalariform thickenings on their walls. No differentiation of roots, shoots or whole plantlets from the calli could be effected under the present cultural conditions employed