Direct differentiation of shoot buds in leaf segments of white marigold (Tagetes erecta L.)

A protocol has been developed for differentiation of shoot buds directly from leaf segments of white marigold (Tagetes erecta L.). Leaf segments were taken from in vitro-proliferated shoots of white marigold established in aseptic culture from shoot tips of field-grown plants. Gibberellic acid (GA) played a significant role in the induction of shoot buds as well as in suppressing callus formation. Shoot buds were induced directly in Murashige and Skoog's (MS) medium supplemented with 14.43 muM GA and 4.44 muM 6-benzyladenine in the absence of any auxin. In this medium two to five shoot buds differentiated from the margins as well as leaf lamina of the lower petiolar segment within 4 wk of incubation. Differentiated shoots grew well and proliferated in the MS medium having 1.1 muM BA and 29.41 muM AgNO3, as it had a beneficial effect on the growth and proliferation of shoots. Shoots were excised, rooted in 0.27 muM alpha- naphthaleneacetic acid (NAA) and transplanted under glasshouse conditions, where they grew and flowered. Data on different morphological characters during flowering under field conditions were recorded for seed-grown control plants, tissue culture-raised primary regenerants (R-0) and first-generation (R-1) plants. It was found that all the economically desired characters of plant height, number and size of flowers per plant, number of viable seeds per flower, and days to full bloom, of the R-1 generation plants were significantly better than the control, thus increasing the commercial value of the tissue culture-raised plants in successive generations.