Flowering phenological trends under the effect of climatic parameters of the arid Mediterranean region: the model of date palm

Flowering is a key event in the life cycle of plants. However, in the last Century, the timing of this major reproductive episode has been disturbed by climate change especially in the arid Mediterranean regions. Monitoring these phenological processes is interesting because it allows to quantify the extend of the ecological perturbation caused by global climate change in this area. We, therefore, investigated the flowering response of male date palms (Phoenix dactylifera L.) to climatic variation for a period of three years in order to establish a flowering calendar that allows us to address its asynchronism. The flowering phenological data were collected for the emergence and the opening of the first spathe events of 180 male genotypes from January to April of each study year. Meteorological data were analyzed at the temporal scale of observations. In this study, a great yearly variability of the reproductive phase within this collection was observed between years. The recorded flowering events revealed a striking trend of precocity for the first spathe emergence and a high stability in the spathe opening stage. Moreover, our findings demonstrated a advancement of the flowering onset and an extended emergence-opening duration. At correlation level, minimum, maximum and mean temperatures, minimum relative humidity and sunshine duration were, involved in the flowering phenological response of the Tunisian male accessions. Our results proved that the date palm flowering is not immune to the climate change effects. This investigation represents an essential phenotypic basis for upcoming flowering-linked genetic research in date palm.