Onion (Allium cepa L.) hybrid seed production: Sugar content variation during the flowering period

Abstract

Honeybees (Apis mellifera L.) are the most used pollinators for onion (Allium cepa L.) seed production. Two types of onion varieties are mainly grown worldwide: hybrids and open pollination (OP) cultivars. Although hybrids offer advantages to bulb growers, seed yields of hybrids are lower than OP cultivars. Since honeybees play a major role in onion pollination, understanding the contribution of the floral rewards to bee visitation is crucial to improve seed yield. The goal of this study is to establish the best moment for the introduction of honeybee hives into onion fields to increase seed yields. To reach this goal, the correlation between sugar compounds in nectar throughout the flowering period and honeybee foraging activity was determined. The sugar profile and bee visits were highly correlated, and fructose concentration was strongly linked to bee frequency of foraging on the onion umbels. The highest number of bee visits was recorded at 70% of flowering. Based on these results, beehives should be introduced once 40–50% of flowering is reached.