Submitted to: International Journal of Food, Agriculture, and the Environment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/11/2004
Publication Date: 1/11/2005
Citation: Malik, N.S., Bradford, J.M. 2004. Reciprocal grafting between early maturing and normal maturing olive varieties: preliminary effects on the nature of juvenility and flowering. International Journal of Food, Agriculture, and the Environment. 2:197-200. Interpretive Summary: Olives normally take 4-6 years to reach maturity before they start to flower and fruit. This is a very long period to wait when one has to develop new cultivars for Texas, based on selection of clones with strong adaptability to Texas conditions. To expedite this process, grafting experiments were performed between a normal maturing variety, 'Manzanillo' (maturing in 4-6 years), and an early maturing variety, 'Arbequina' (maturing within 1-2 years) to study if the rootstock of early maturing variety can expedite the maturity process in scion from the normal maturing variety. The experiments demonstrated that roots had no control over the maturity of shoots. Additional experiments were conduted to see if scions from mature trees would continue to produce flowers when grafted on rootstock of immature trees. This experiment clearly showed that shoots from mature trees indeed continue to produce new growth capable of flowering even on immature root. This experiment will now be conduted using multiple varieties to see if the observed phenomenon is of universal nature. If the results were consistent in the future studies then this will provide a powerful tool to expedite the maturity process in olives, leading to quicker development of new cultivars.
Technical Abstract: Reciprocal grafting was performed between young trees (18 months old) of early maturing (within 1-2 years) and normal maturing (4-6 years) varieties of olives. Scions of an early maturing variety ('Arbequina') grafted on young rootstocks of a normal maturing variety ('Manzanillo'), and grown for 7 months in greenhouse conditions, produced flowers when subjected to flower-inducing chilling periods. Conversely, scions from juvenile 'Manzanillo' trees grafted on an early maturing variety 'Arbequina' failed to produce flowers under similar conditions. In addition, scions taken from a mature tree (L712; that flowered after 4 years) when grafted on juvenile rootstock plants of normal maturing varieties ('Manzanillo' and 'Mission') and allowed to grow for 8 months, also produced flowers when subjected to flower-inducing conditions. The results indicate that once an olive shoot has been matured or conditioned to receive flowering stimulus, it continues to produce flowers even on nodes that were formed after it had been grafted on roots of a plant that had not been matured. Apparently, olive roots do little to control the ability of the shoot to be receptive to chilling stimulus for flower induction in olives. However, the possibility exists that the roots may play a role in flower or fruit development in olives.