Influence of explant types, non-embryogenic synseed and reduced oxygen environment on in vitro conservation of Bacopa monnieri (L.) Wettst

The effect of using encapsulated shoot tips (ST) and nodal segment (NS) explants, in combination with mineral oil (MO) overlay, for in vitro regeneration and efficient midterm conservation of Bacopa monnieri (IC468878), a medicinal herb with potent nervine properties is described. On a standard multiplication medium [Murashige and Skoog (MS) containing 0.2 mg l−1 benzyladenine (BA)] after 8 wk of culture, the number of shoots regenerated from ST (17.50 ± 0.50) to NS (19.10 ± 1.20) were not significantly different; however, the shoot length regenerated from NS (7.30 ± 0.70 cm) was significantly higher than ST (2.50 ± 0.30 cm). Encapsulation of ST explants did not have any significant effect on the number of shoots (18.10 ± 1.00) and shoot length (3.50 ± 0.30 cm), while there was significant decrease in shoot number (10.30 ± 1.0) and shoot length (1.50 ± 0.40 cm) in NS explants. In general, use of MO overlay resulted in highly significant reduction of growth and increase in survival of cultures. The combined strategy of encapsulation and MO overlay led to growth reduction in terms of number of shoots (2.50 ± 0.30 in ST, 2.30 ± 0.20 in NS) as well as shoot length (0.50 ± 0.02 cm in both explants). After 12-mo in vitro conservation, encapsulated NS explants in combination with MO overlay gave the highest survival rate (91.6 ± 5.7%) and number of shoots (21.4 ± 1.6). This is the first report on success of combining two slow-growth strategies of reduced oxygen environment and synseed technology for midterm (12 mo) in vitro conservation of germplasm.