Organogenesis of stem and leaf protoplasts of a haploid golden delicious apple clone (Malus Xdomestica Borkh.)

Summary Highly viable protoplasts were isolated in large numbers from in vitro-grown leaf and stem tissues of a haploid clone of the apple scion cultivar Golden Delicious (Malus Xdomestica Borkh.). Protoplasts from both sources divided rapidly to give microcallus, when cultured in a modified Kao and Michayluk-based medium. Following two successive subcultures for callusing, shoot buds were regenerated from such calli, on half-strength Murashige and Skoog medium with an increased concentration of group B vitamins and containing 5.0 mg.l^-1 6-benzyl-aminopurine and 0.1 mg.l^-1 l-naphthaleneacetic acid (for the leaf protoplast-derived calli) or 4-indole-3yl-butyric acid (for stem protoplast-derived calli). The mesophyll protoplast-derived shoots were enfeebled and vitrified, in time with their ultimate death. Conversely, for those shoots deriving from the stem protoplasts, in vitro propagation was successfully achieved. This is the first report on the successful isolation, culture and organogenesis from stem protoplasts of a woody plant genotype.Abbreviations BAP 6-benzylaminopurine - FPE final plating efficiency - IBA 4-indole-3yl-butyric acid - IPE initial plating efficiency - f wt fresh weight - KM Kao and Michayluk (1975) - MES 2-N-morpholino ethane sulfonic acid - MPE intermediate plating efficiency - MS Murashige and Skoog (1962) - NAA l-naphthaleneacetic acid - PVP-10 polyvinylpyrrolidone (Av MW 10,000)