Carbon nutrition of Ottawa 3 apple rootstock during stages ofin vitropropagation

SummaryThe influences of the carbon sources, sorbitol, sucrose, glucose and fructose on in vitro shoot proliferation and rooting of Ottawa 3 apple rootstock were compared. On proliferation media supplied with 10, 30, 50 and 70 gl−1 of each carbon source, a concentration of 30 gl−1 of each source was optimal for quantitative shoot growth. Among cultures grown on different carbon sources, the highest mean leaf/stem ratio occurred on sucrose medium and the lowest mean number of shoots and shoot length occurred on fructose and sorbitol media, respectively. However, normal growth of cultures occurred only on medium with 30 gl−1 sucrose. The presence of sucrose at other concentrations tested, or of sorbitol, glucose and fructose between 10 and 70 gl−1 including various proportions of sorbitol in combination with sucrose (30 gl−1 total), produced abnormal growth. On rooting media supplied with 10–70 gl−1 of each carbon source, 100% rooting occurred after two weeks on medium with 30 gl−1 sucrose. Rooting was intermediate on corresponding glucose and fructose media and poor on sorbitol medium.