Comparative studies on nectar from two self-fertile and two self-sterile cultivars of quince (Cydonia oblonga Mill.) and their attractiveness to honeybees

Abstract

SummaryCross-pollination is of primary importance for quince (Cydonia oblonga), whose flowers reward pollinators with pollen and nectar. Characteristics of the nectar from two self-fertile (SF) and two self-sterile (SS) cultivars of quince were compared in a 3-year study, in order to establish if the two fertility groups differed from each other in terms of nectar production and/or insect attraction. The volume of nectar secreted per flower per day was measured using calibrated capillaries. The concentrations of nectar sugars were determined using a hand-held refractometer. The composition of nectar sugars was analysed using thin layer chromatography and densitometry. The quantity and quality of the nectar varied between years, cultivars, and fertility types. The volumes of nectar ranged from 0.40 – 5.30 µl flower–1 d–1 over the 3 years. The concentrations of sugars in the nectar produced flower–1 d–1 averaged ≥ 20% (w/w) in all cultivars, and ranged from 21.80 – 35.60% (w/w) over the 3 years. Significantly lower volumes of nectar were measured in the SF cultivars than in the SS cultivars in both years of the study. However, the concentrations of sugars in the nectar were not significantly lower in the SF group. The total sugar content of nectar varied between 160.59 – 347.65 mg ml–1. The main sugar component in the nectar was sucrose, followed by glucose and fructose. Differences in the composition of nectar sugars could not be correlated with the two fertility groups. Our data showed that, although certain properties of their nectar make SS cultivars more attractive to honeybees than SF cultivars, members of the latter group can also attract sufficient numbers of bees to carry out cross-pollination, which is beneficial to both fertility types of C. oblonga.