In vitro propagation and maintenance of genetic male sterility in marigold

A micro propagation protocol was established for the mass multiplication of selected male sterile line and an established cultivar Pusa Narangi Gainda during the year 2001–2002. Explants viz. shoot tips, nodal segments and flower buds were treated with HgCl₂ solution for different durations (0 min-3min) for surface sterilization. The cultures were incubated at 25° C± 2°C under 16 h photoperiod. Treatment of explants of Apetalous Male Sterile Line and Pusa Narangi Gainda with HgCl₂ (0.1%) for 2 minutes gave highest per cent uncontaminated growing cultures (90.00 and 89.00, respectively). Among the explants, shoot tips were found to be better explants (56.59%) for culture establishment as compared to nodal sections (43.83%). Highest per cent establishment was recorded in Pusa Narangi Gainda (100%) when shoot tips were cultured on MS+BAP (10μM). In case of male sterile line, maximum establishment (95.67%) was obtained when the explants were either cultured on MS+BAP (10μM) or MS+BAP (10μM)+NAA (2μM). Maximum shoot proliferation per explant was recorded in MS + BAP (10μM) + NAA (2μM) in Pusa Narangi Gainda (3.33) and Apetalous Male Sterile Line (3.00). More shoot length after one month of culture was recorded in Pusa Narangi Gainda (0.81 cm) as compared to the male sterile line (0.51 cm). Shoot length was recorded maximum (3.48 cm) when basal MS medium was supplemented with BAP (10μM) + NAA (2μM). Apetalous Male Sterile Line had maximum number of roots (16.67) either with NAA (10μM) or IBA (6μM), whereas in Pusa Narangi Gainda maximum number of roots per shoot (15.53) were obtained when MS medium was supplemented with NAA (2μM). The plantlets produced under in vitro conditions were transplanted into pots containing sterilized cocopeat and kept for hardening. In cv. Pusa Narangi Gainda survival rate was 80%, whereas in case of Apetalous Male Sterile Line, it was 73%. The hardened plantlets were successfully transferred to the field.