Impact of plant growth regulators (PGRs) on callogenesis and artemisinin content in Artemisia annua L. plants

Callus cultures were initiated from leaf explants of Artemisia annua L. plants for artemisinin production using Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of plant growth regulators (PGRs), viz., BAP, NAA, 2,4-D and TDZ. The combination of all PGRs at different concentrations showed a better response in induction of undifferentiated friable calli in the light phase as compared to the dark phase. The calli of transgenic plants over-expressing hmgr gene yielded a biomass of 0.13 g dw/explant in the light in comparison to 0.06 g dw/explant in the dark, when grown on MS medium supplemented with BAP (1.0 mg L^-1) and NAA (2.0 mg L^-1). The non-transgenic (untransformed plant) calli, however, yielded a biomass of 0.10 g dw/explant in the light when grown on MS medium supplemented with the same concentrations of BAP and NAA, while yield was 0.06 g dw/explant in the dark in MS medium supplemented with BAP (1.0 mg L^-1) and 2, 4-D (1.0 mg L^-1). Further, the maximum artemisinin content (0.006% on dw basis) was recorded in both transgenic and non-transgenic calli that were grown on MS medium supplemented with BAP (1.0 mg L^-1) and NAA (2.0 mg L^-1) under light phase.