Standardization of in vitro Culture Establishment and Proliferation of Micro-Shoots in African and French Marigold Genotypes

Abstract

Marigold is native to Mexico and one of the commercial loose flower crops in India. In general it is commonly propagated through seeds, but some ornamentally high valued petaloid and gynomonoecious lines can only be maintained through vegetative propagation. Initial in vitro axenic culture establishment, poor multiplication rates, excess callusing and vitrified cultures are the major hindrances in its commercial micro-propagation. Therefore, the objective of the present investigation was to develop efficient in vitro protocol for mass multiplication of commercially popular African and French marigold cultivars Pusa Basanti Gainda (PBG) and Pusa Arpita (PA) respectively. Nodal segments were chosen as explant of these two open field cultivars. Explants were pre-treated with carbendazim (0.2%) + metalaxyl (0.2%) + 8-hydroxy quinoline citrate (200 mg/l) for 60 minutes followed by surface sterilization with 0.1% HgCl2 for 4 minutes to eliminate the microbial contamination. Highest culture establishment (69.44%) and earliest bud emergence (4.45 days) was recorded in Murashige and Skoog (MS) medium supplemented with BAP (2.0 mg/l) and NAA (0.05 mg/l). Among the different proliferation treatments, 100% proliferation was recorded in MS medium devoid of any growth regulators, MS + 0.5 mg/l Kinetin + 0.1 mg/l NAA and 0.5 mg/l BAP + 0.1 mg/l NAA + 2.5 mg/l AgNO3 supplemented media. The maximum numbers of quality shoots (4.3, 18.8, 64.2 and 208.2 shoots/explant) were obtained on MS medium supplemented with 0.5 mg/l BAP + 0.1 mg/l NAA + 2.5 mg/l AgNO3 in 30, 60, 90 and 120 days after culture respectively. This protocol is highly useful for mass multiplication of true-to-type, disease free planting material as well as helpful in long term maintenance of germplasm lines.