Phenological and aeropalynological survey in an olive orchard in Umbria (Central Italy)

The olive tree Olea europaea L. is a resource of notable value from an economic and landscape point of view in Central Italy. This study examined two cultivars (Giarraffa and Ascolana) grown in an associative stand in an experimental olive orchard, to verify the possibility of introducing new olive cultivars into Umbria. The analyses were carried out at three different altitudes in the olive orchard following criteria used for non-homogeneous samplings in order to minimize the effect due to steepness. Since the number of trees of the two cultivars is different, the sample sizes were different for the two cultivars. Phenological observations of the above mentioned cultivars and the evaluation of the pollen flow, done by using a portable pollen trap inside the olive orchard, were carried out over two seasons (1998-1999). The start of initial phenological phases differed in the two cultivars, but the differences became less evident during phases of anthesis. In aeropalynological respect, it appears that, in a hill species such as the olive tree, the flowering is correlated with altitude. Comparing the aeropalynological data from the distant pollen trap and those collected in the olive orchard, it is clear that the periods of pollen release are very similar in the two cultivars, and there is a clear synchronism in the peak pollen release. It is concluded that in Central Italy the pollen grains of Giarraffa cultivar are well compatible with the Ascolana cultivar from a phenological and aeropalynological point of view.