Increased root and shoot production during micropropagation of cherry and apple rootstocks: effect of subculture frequency

Shoot cultures of apple rootstock cv. M9 and cherry rootstock cv. F12/1 wer e established and then divided into several sublines that were subcultured at 28-42-day intervals. Consequently, similarly aged cultures received vari ous numbers of subcultures. Cultures kept at 24 degrees C showed an increas e in shoot and root production over time. There were differences in shoot a nd root production between apple lines, but there were no differences among sublines. In cherry, altering the subculture interval affected rooting com petence, which increased with time. Cherry cultures maintained at 4 degrees C gave rise to cultures that were as easy to root as cultures kept at 24 d egrees C with more frequent subculturing. We conclude that total time in cu lture is the most important factor bringing about physiological changes in these genotypes of micropropagated apple and cherry.