Composition of floral nectar and its seasonal variability in sour cherry cultivars

The sugar composition of floral nectar was studied in 17 sour cherry cultivars in Újfehértó in 1997-2000. All samples contained the three most frequent sugar components: glucose, fructose and sucrose, similarly to our previous data. The ranking of the floral nectar in sour cherry cultivars based on sucrose content was the following: 'Újfehértói fürtös' and 'Pándy 48' reached the threshold value of bee visitation in at least three seasons, and a significant amount of sucrose was detected in the flowers of 'Érdi jubileum AB' and 'Érdi bőtermő' as well. The above cultivars proved to be the most valuable in Újfehértó from the viewpoint of apiculture. According to the ranking based on fructose content, which considers human sensation of taste, the most favourable cultivars were 'Újfehértói fürtös', 'Meteor USA' and 'Korai pipacs'. Based on total sugar content the secretory products preferred by bees were those of 'Újfehértói fürtös' (in three seasons); 'Korai pipacs', 'Érdi nagygyümölcsű', 'Sárándi S/Gy', 'Debreceni bőtermő', 'Kántorjánosi 3', 'Montmorency' and 'Meteor USA' (in two seasons). The ratio of nectar sugars, based on the Baker-quotient, S/(G+F), was sucrose-dominant at least in one season in 'Érdi jubileum AB', 'Érdi nagygyümölcsű' and 'Pándy 48'; hexose-rich in 'Korai pipacs', 'Kántorjánosi 3' and 'Montmorency'; all other cultivars had a sucrose-rich nectar. The nectar of all studied sour cherry cultivars possessed a composition preferred by bees. The basis of bees' nectar preference is the ratio, quantity and concentration of nectar sugar components, which were influenced by the effects of season to a high degree, differing from data in literature. From the viewpoint of nectar composition and concentration the most favourable temperature was around 20 °C.