Morphogenetic response to plant growth regulators in transformed and untransformed Hypericum perforatum L. clones

This study examined the effects of different exogenous auxins and cytokinins at 0.1-5.0 mg·l-1 concentration on shoot cuttings of two H. perforatum clones transformed with a wild agropine strain of A. rhizogenes and one untransformed clone. Their sensitivity to the auxins varied and showed concentration-dependent behavior, and the response to auxins differed between the transgenic clones. The number of cuttings of transgenic clones capable of root formation, and the onset of rooting on most of the media with auxins lagged behind the control. The number of differentiated shoots of the transgenic clones on hormone-free medium was two to three times higher than that of the untransformed control. Regenerated shoots of the transgenic clones on basal medium branched much less than the nontransgenic clone. The transgenic and control clones differed in their ability to form shoots on media supplemented with cytokinins. Increased cytokinins led to differentiation of shorter shoots with fewer leaf pairs. Because gene expression studies have shown integration of rolABC genes, their possible impact on the type of morphogenetic response is discussed.