Circumventing phenolic exudation and poor survival in micropropagation of marigold

Abstract

Marigold is one of the popular ornamental crops grown mostly for loose flower production and garden display. It is usually propagated through seeds, but some germplasm including male sterile lines (petaloid and gynomonoecious forms) can only be maintained through vegetative means of propagation. Year round production and maintenance of true-breeding lines can be possible by employing efficient tissue culture techniques. However, exudation of phenols from explants and poor ex vitro survival of marigold plants are the major hindrances. Therefore, the present investigation was carried out with an objective to standardize the protocol for controlling phenolic exudation from nodal explants and also enhancing the ex vitro survival of four marigold genotypes viz., Pusa Arpita, Pusa Basanti Gainda, Siracole Orange and Siracole Yellow. The exudation of phenolic compounds from nodal explants was significantly controlled by incorporating 125 mgl-1 ascorbic acid into the culture induction medium supplemented with BAP (2.0 mgl-1) + NAA (0.1 mgl-1) in all the genotypes. Marigold micro-shoots cultured on ½ MS liquid rooting medium supplemented with 0.5 mgl-1 IBA showed highest rooting percentage (99.00%) which was followed by ½ MS + 0.5 mgl-1 NAA (98.75%). Early root induction (5.88 days), longest roots (2.78 cm), moderately high number of roots (47.56) per shoot and highest ex vitro survival (98.75%) were observed with ½ MS + 0.5 mgl-1 NAA. Among the different hardening strategies employed, lowest mortality (11.55%), maximum plant height (15.15 cm) and leaf number (20.95) were noted in plants that were hardened in disposable polypropylene glasses.