Micropropagation system for Carnation (Dianthus caryophyllus) - an important ornamental plant

Abstract

The present investigation was carried out on an important ornamental plant Dianthus caryophyllus belonging to family Caryophyllaceae. The different vegetative parts i.e. nodal explant, shoot apices, stem and leaves were excised from field grown mature plant and thereafter planted on variously supplemented Murashige and Skoog’s medium for multiple shoot proliferation, callus induction and de novo adventitious root and shoot formation Dianthus exhibits a good degree of propensity of multiple shoot proliferation from nodal and shoot apex segments. Multiple shoot proliferation from nodal explants was observed on MS medium supplemented with BAP(4.4-8.8µM) or Kn(4.65-9.30 µM)either alone or in conjunction with lower concentrations of NAA(1.47-7.35µM). Out of all the combinations tried, best results were, however, obtained on MS+BAP(4.4µM) where 16-18 shoots were formed from single axillary bud and shoot apex. The present material had a great organogenic potential as it exhibited a high efficiency of de novo adventitious root and shoot formation directly from the stem segment. Profuse growth of lateral roots occurred on the entire surface of stem segment along with adventitious shoot formation on lower concentrations of NAA(7.35µM). These roots were short and bore root hairs profusely. Further incorporation of CM(15%) to the NAA supplemented medium considerably enhanced the rooting where entire segment was covered over with clumps of roots. The roots were thin, white having dense root hairs. A high efficiency of adventitious shoot formation from the stem segment was observed. Stem segments cultured on MS medium supplemented with NAA(1.47-7.35µM) either alone or in conjunction with BAP(4.4µM) or Kn(9.30µM) and MS + BAP(4.4µM) or MS+ Kn(9.30µM) produced adventitious shoots directly on the surface of stem explants without the formation of intervening callus. 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(7.35µM) showed the best results where rooting occurred. Attempts are underway to establish regenerated plantlets into the soil. Callusing of the nodal segment, shoot apices, leaf and stem segments occurred immediately after culturing on optimal chemical milieu. Murashige and Skoog’s agar gelled medium supplemented with NAA (29.4 µM), with or without CM (15%) or 2,4-D (19.48 µM) + Kn(4.65 µM) turned out to be optimal for initiation and sustained growth of calli from different plant parts. The calli were pale yellow, friable and fast growing. Formation of green friable callus from the leaf explant on 2,4-D (4.87µM) + BAP(0.88 µM) + 2000mg/l casein hydrolysate was the best medium reported. The callus thus formed from different vegetative parts on the medium were more or less identical in morphology. The calli obtained from all the parts were heterogenous being composed of parenchymatous ovoid, oblong, semicircular cells or those with aberrant shapes. 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 organogenetic differentiation could be effected from the calli on the various media tried.