TEMPORARY MODIFICATION OF ADULT FILBERT PROLIFERATION CAPACITY BY SEQUENTIAL SUBCULTURES - INTENSIVE PRUNING AS A PRETREATMENT FOR IN-VITROREINVIGORATION

The improvement in shoot production of filbert (Corylus avellana L.) a dult tissues by sequential in vitro subcultures and intensive pruning was studied. Improved and sustained production of adult shoots is poss ible by repeated subculturing in the presence of high cytokinin concen trations, which seem important for stabilizing the response and induci ng a transient increase in proliferation. Intensive pruning increases proliferation in initial explants and facilitates the establishment an d maintenance of culture lines. Rooting capacity is also enhanced by s equential in vitro subcultures, but stabilizing the response takes lon ger than with shoot proliferation. The increased capacity of adult tis sues for shoot proliferation and rooting are similar to those obtained using juvenile plants as a source of explants, and could be explained as a reinvigoration induced by in vitro sequential subcultures.