Olive (Olea europaea L.) inflorescences, formed in lateral buds, flower in spring. However, there is some debate regarding time of flower induction and inflorescence initiation. Olive juvenility and seasonality of flowering were altered by overexpressing genes encoding flowering locus T (FT). OeFT1 and OeFT2 caused early flowering under short days when expressed in Arabidopsis. Expression of OeFT1/2 in olive leaves and OeFT2 in buds increased in winter, while initiation of inflorescences occurred i n late winter. Trees exposed to an artificial warm winter expressed low levels of OeFT1/2 in leaves and did not flower. Olive flower induction thus seems to be mediated by an increase in FT levels in response to cold winters. Olive flowering is dependent on additional internal factors. It was severely reduced in trees that carried a heavy fruit load the previous season (harvested in November) and in trees without fruit to which cold temperatures were artificially applied in summer. Expression analysis suggested that these internal factors work either by reducing the increase in OeFT1/2 expression or through putative flowering repressors such as TFL1. With expected warmer winters, future consumption of olive oil, as part of a healthy Mediterranean diet, should benefit from better understanding these factors.
Bibliographical noteFunding Information:
We dedicate this work to the late Prof. Shimon Lavee who introduced us all (and many others worldwide) to olive biology. Shimon helped design the experiments and interpret the results. He will be greatly missed. We thank the anonymous reviewers for their helpful comments. We thank Ravit Eshed and Eviatar Steiner for their excellent advice on strategies for construct preparation for plant transformation, Benjamin Avidan and Oren Ostersetzer-Biran for their support at the beginning of this project and the team of ‘Gadash Tsabar Kama’ for providing access to trees in their commercial orchard. The research is funded by the Israeli Science Foundation – the Charles H. Revson Foundation (grant no. 1464/07) to A.S., the Chief Scientist Ministry of Agriculture and Rural Development, Israel (grants no. 837-0132-11 and no. 12-02-0002) to A.S. and by grant P11-AGR 7992, Junta se Andalucía, Spain to F. P.-A.
© 2017 John Wiley & Sons Ltd
- Olea europaea
- alternate bearing
- flowering locus T
- fruit load