The expression of SmG10H and accumulation of swertiamarin in hybrid clones. A, Variation for level of SmG10H expression. B, Swertiamarin content. Sm, S. mussotii; Bs, B. scorzonerifolium; B24 and B132, hybrid clones from combination B; C47, hybrid clone from combination C; A6, hybrid clone from combine A. Bars represent the standard error of the mean; t test, *, P < 0.05.