Requirement for sorbitol (D-glucitol) as carbon source for in vitro propagation of Malus robusta No. 5
Meristem tip explants of Malus robusta Rehd. No. 5 were successfully initiated in vitro on nutrient medium with sorbitol but not with glucose, sucrose, or fructose, each supplied at 30 g/L. Cultures, subsequently subcultured and multiplied on sorbitol medium, produced the highest number of shoots and had the highest shoot fresh and dry weights, followed in descending order by cultures grown on glucose, sucrose, and fructose media. Decreasing the proportion of sorbitol and increasing that of sucrose in the carbon source fraction (30 g/L total) resulted in decreasing shoot number and shoot weight accompanied by increasing leaf/stem ratio and compactness of the shoot cultures. After 32 days on agar medium with 0.5 mg/L indolebutyric acid in the presence of either sorbitol or sucrose, 85% rooting was achieved.