Identification of Floral Volatiles and Pollinator Responses in Kiwifruit Cultivars, Actinidia chinensis var. chinensis.

Abstract

Volatiles emitted from unpollinated in situ flowers were collected from two male cultivars, 'M33', 'M91', and one female cultivar 'Zesy002' (Gold3) of kiwifruit (Actinidia chinensis var. chinensis). The samples were found to contain 48 compounds across the three cultivars with terpenes and straight chain alkenes dominating the headspace. Electrophysiological responses of honey bees (Apis mellifera) and bumble bees (Bombus terrestris) to the headspace of the kiwifruit flowers were recorded. Honey bees consistently responded to 11 floral volatiles from Gold3 pistillate flowers while bumble bees consistently responded to only five compounds from the pistillate flowers. Nonanal, 2-phenylethanol, 4-oxoisophorone and (3E,6E)-α-farnesene from pistillate flowers elicited responses from both bee species. Overall, honey bees were more sensitive to the straight chain hydrocarbons of the kiwifruit flowers than the bumble bees, which represented one of the main differences between the responses of the two bee species. The floral volatiles from staminate flowers of the male cultivars 'M33' and 'M91' varied greatly from those of the pistillate flowers of the female cultivar Gold3, with most of the bee active compounds significantly different from those in the Gold3 flower headspace. The total floral emissions of 'M33' flowers were significantly less than those of the Gold3 flowers, while the total floral emissions of the 'M91' flowers were significantly greater than those of the Gold3 flowers.