Improved plant regeneration from cultured leaf segments in peanut (Arachishypogaea L.) by limited exposure to thidiazuron

Bud primordia were induced from leaf segments, which were harvested from yo ung seedlings of Spanish type peanut (Arachis hypogaea L. cv. Chico), on 0. 8% agar-solidified medium containing Murashige and Skoog (MS) basal salts s upplemented with B5 vitamins, 1 mg/l NAA and various cytokinins such as ben zyladenine (BA), isopentenyladenine (2ip), kinetin (KIN), chloropyridylphen ylurea (4PU), thidiazuron (TDZ), zeatin (ZTN) in different concentrations. Among the cytokinins tested, TDZ was found to be the most efficient for ind ucing bud primordia. However, continuous culture on TDZ-containing media in duced abnormal development of these primordia, and they failed to grow into plantlets. Histological observations revealed that the malformation most o ften obtained was a shoot-like structure which lacked shoot apical meristem (SAM) and had disorganized vascular bundles. For normal shoot regeneration , it was necessary to limit the culture period of the explants on TDZ-conta ining medium to 7 days at 10 mg/l or 21 days at 1 mg/l and then transfer th em onto plant growth regulator-free medium. The percentage of conversion fr om shoot buds to shoots was 34.7%. When shoots were removed from the explan ts and transferred onto basal medium containing 1 mg/l NAA, all regenerated shoots readily rooted and successfully acclimatized. All of the acclimatiz ed plants produced viable seeds in the greenhouse condition. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.