In Vitro Cloning of Chrysanthemum Paludosum – An Important Ornamental Plant.

Abstract

The current investigation was carried out on an important ornamental plant Chrysanthemum paludosum belonging to family Asteraceae. Various vegetative parts like nodal segments, shoot apices, stem segments and leaves were excised from a healthy and mature field grown plant. The different explants were surface sterilized and inoculated on Murashige and Skoog’s medium (1962) supplemented with various growth regulators for multiple shoot proliferation, callus induction and de novo adventitious shoot and root formation. Chrysanthemum paludosum exhibited good degree of multiple shoot proliferation from nodal explants. Multiple shoot proliferation was observed on MS medium supplemented with BAP (4.44 - 17.76 µM) or Kn (4.65 – 18.6 µM) in conjunction with lower concentrations of NAA (2.68 – 5.37 µM). Amongst these various combinations, best results were obtained on NAA (2.685 µM) + Kn (4.65 µM) where 20-22 shoots were formed from a single axillary bud. The plants exhibited high degree of propensity for de novo adventitious root and shoot formation directly from the stem and leaf segments. Prolific de novo root formation from leaf explants was observed on different concentrations of NAA, IBA and IAA, whereas direct root formation from stem segment occurred only on 22.84 µM of IAA. Roots formed on surface of explants bore dense root hairs while those growing inside the medium did not bear any root hairs. Different hormones of different concentrations had varied effects on morphology of roots formed. De novo adventitious shoot formation was observed directly from the stem and leaf segments. From leaf explant, de novo shoots were regenerated on MS + NAA (5.37µM) + Kn (4.65µM) with maximum of 12-15 shoots after 4 weeks. Out of various combinations tried, de novo shoot formation occurred on MS medium supplemented with Kn (4.65 µM) and lower concentrations of NAA (2.85 – 5.71 µM) and IBA (2.45 – 4.9 µM). From stem segments, de novo shoot regeneration occurred on IBA (2.45 – 19.6 µM) + Kn (4.65 µM) with maximum of about 8-10 shoots. Callusing from stem and leaf segments occurred on MS medium variably supplemented with plant growth regulators in different combinations. MS medium supplemented with Kn (4.65 µM ) and higher concentrations of NAA (21.48 µM) or IBA (19.6 µM) was found to be the best for callus induction from leaf and stem segments respectively.. The calli obtained from leaf and stem segments varied slightly in morphology. All the calli were heterogeneous and composed of cells of various shapes and sizes. The calli also showed significant histogenetic differentiation in form of tracheids that possessed reticulate thickenings on their walls. The calli formed from stem segments on IBA (2.45-4.9 µM) + Kn (4.65 µM) exhibited high frequency shoot differentiation from the callus. The leaf callus exhibited only rhizogenic differentiation on MS + NAA (10.74 µM) + Kn (4.65 µM) after six weeks of culturing forming long, thin and slender roots.