FACTORS EFFECTING ADVENTITIOUS SHOOT REGENERATION FROM LEAF EXPLANTS OF QUINCE (CYDONIA-OBLONGA)

A procedure for adventitious shoot regeneration from leaf explants of quince (Cydonia oblonga Mill.) using thidiazuron (TDZ) was developed. Excised leaves of cultures grown on Murashige and Skoog (MS) medium containing 5 mu M benzyladenine (BA) and 0.9% Gibco Phytagar were used. Several experiments were conducted to determine optimum concentrations of thidiazuron, cr-naphthaleneacetic acid (NAA) and sucrose. When the medium contained 1.5 mu M TDZ and 2.5 mu M NAA, 85% of Uhe discs regenerated shoots with an average of eight shoots per leaf disc. An incubation period of three weeks in the dark was necessary for optimum shoot regeneration. Leaves excised from four to six-week-old cultures gave a higher percent shoot regeneration than leaves from cultures older than six weeks. Regeneration percentages were significantly reduced when sucrose concentration in the medium was less than 3%. A significantly higher percentage of shoots regenerated when leaf discs were placed on the regeneration medium abaxial side down as compared to the adaxial side. Regenerated shoots were cultured on MS medium containing 5 mu M BA and rooted on half-strength MS medium containing 10 mu M NAA. Rooted plantlets were acclimatized to greenhouse conditions for evaluation of any somaclonal variation. The importance of these findings are discussed in relation to in vitro improvement of plants.