PLANT-REGENERATION FROM LEAF MESOPHYLL PROTOPLASTS OF INVITRO CULTURED SHOOTS OF A COLUMNAR APPLE

By culturing shoot cultures of apple in dim light (1 μEm−2s−1) for 6 days before digestion of the leaves and by using an enzyme mixture containing pectolyase (0.01 % w/v), a large number of viable protoplasts were obtained (2–4 × 106 protoplasts/g leaf tissue). Addition of ABA (10−4M) to the plasmolyticum increased the number of initial dividing protoplasts from 8 to 12 % in a modified PPP medium including 1 mg zeatin/1 and 2 mg/1 2,4-D. Sucrose as plasmolyticum in the protoplast growth medium improved survival and increased the divisions during the initial growth phase. Thidiazuron (1 mg/l) combined with 1 mg/l 2,4-D improved the yield of protoplast divisions in ABA-treated cells to 15 %. Regeneration of shoots, initially cultured in 0.5 mg/1 BAP and 2 mg/1 2,4-D, was induced by thidiazuron (1 or 2 mg/1) in MS-medium with 0.5 mg NAA/1. The protoplast-derived shoots were diploid as were the original columnar apple shoots. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.