ADVENTITIOUS SHOOT FORMATION IN TULIP - HISTOLOGICAL ANALYSIS AND RESPONSE TO SELECTIVE AGENTS

On explants taken from young floral stems of tulip (Tulipa gesneriana L.) adventitious shoot formation was induced. The shoots were formed d irectly from the explants without an intermediate callus phase. More s hoots developed on explants taken from dry-stored bulbs than from bulb s stored in ice. At the basis of the shoots a meristem was formed that developed into a new bulb. The ability to form this bulb meristem was compared in 8 cultivars, and was highest in Lucky Strike and Monte Ca rlo. Adventitious shoot formation was initiated in the first two subep idermal cell layers and a number of cells of the original explant cont ributed to the shoot formation. To avoid the formation of chimeric tra nsformed shoots in future transformation, an optimal selection system was established. For selection purposes, the aminoglycoside antibiotic s were not very effective in inhibiting shoot formation, since tulip t issue showed a high tolerance for kanamycin, while G418 and hygromycin induced severe necrosis of the explants at low concentrations. In con trast, the herbicides phosphinothricin and glyphosate were very effect ive and offer good perspectives to be used for selection of transforme d shoots.