Capacità olfattive e di memoria in Apis mellifera Ligustica (Spin.) quali mezzi da poter utilizzare per l'impollinazione di specie non attrattive: il caso dell'Actinidia deliciosa.

Good pollination is essential in order to obtain large kiwifruits. While honey-bees can be the primarily pollinators of Actinidia deliciosa if just-attracted from its flowers. Infact, pollen can also be brought to female flowers of kiwi by wind and other insects. In some areas of Italy pollination problems exist due to the simultaneous flowering of other crops that are more attractive to honey-bees. In order to evaluate the effects of different treatments on kiwi fruit growth and quality, trials were carried out in 1998 and 1999 and again in 2001 and 2002 to: 1) measure the relative contribution of wind and insect pollination, 2) increase the attraction of honey-bees towards kiwi flowers, 3) improve pollination by artificially applying pollen. Before flowering, some fruiting shoots were bagged with nets to allow only wind pollination. Some beehives were fed with Actinidia male pollen (induction feeding) to increase the attractiveness of the kiwi flowers. The experiment was based on the good memory of honey-bees for the scent of the flowers (the use of male pollen of kiwi flowers in sucrose solution carried this function). During flowering, pollen was collected from flowers of male vines and the pollen was used to artificially pollinate just-opened flowers using a "tennis ball" or a hand sprayer, after making a suspension in water. Untreated flowers were used as the control. To better evaluate the effect of artificial pollination, immediately after the pollen was applied, some of the flowers were bagged with nets to prevent any insect visits. The results of the trials showed that preventing insect pollination caused a marked fruit drop ( 30%), reduced fruit growth (- 50%), and resulting the fruit was rounder shaped and had fewer seeds. Induction feeding of bees resulted in an increase in Actinidia pollen gathered by the bees, indicating an improved attractiveness towards Actinidia flowers. Under both artificial pollination systems tested, the fruit tended to be larger than the control, regardless of flower bagging after pollination. In contrast, a significant decrease in fruit growth was observed in the control when flowers were bagged.. These results indicate that the pollination requirements of the flowers were completely satisfied by the artificial systems tested. The fruits from the artificially pollinated flowers had a higher length-to-diameter ratio and more seeds; they tended to have a higher soluble solids content and a lower flesh firmness at harvest. The results show that kiwi pollination problems can be reduced or eliminated by introducing induction feeding of beehives and/or by using artificial pollination, but the use of honey bees was less expensive.