Vicia faba is a legume crop valued for its high protein content and ability to fix nitrogen. The UK is a key producer of faba beans, which are likely to be increasingly important as a less environmentally harmful protein source. However, without insect pollination, V. faba yield declines by 32.9% on average. When faced with continuing bee declines, it is imperative that more is done to understand how floral traits of V. faba may be used to improve crop yield through pollinator attraction.

In this project, novel variation has been identified between commercial lines of V. faba in reward, attraction, and access traits. Using this variation, a hypothesis was formulated that V. faba lines possessing floral traits considered to be more attractive to bees would receive more bee visits. Data from two years of field trials supported this hypothesis, with bees showing preference for lines with more flowers and superior nectar sugar content. Field trials also supported the hypotheses that open pollination would have a positive effect on V. faba yield, and that lines with more attractive floral traits would receive a larger yield benefit with open pollination. These results have shown for the first time that V. faba floral trait variation affects bee attraction in the field and has significant effects on the pollination of the crop.

Following field trials, preferences experiments using Bombus terrestris foragers in controlled condition were used to identify V. faba floral traits likely to be most important for bee attraction. Together, field and controlled condition experiments suggested that floral colour, nectar concentration, display size, and scent are traits most likely to increase pollinator attraction to the crop. These experiments have also contributed to the wider understanding of pollinator attraction, adding to evidence that bees show preference for purple colours.

The evidence presented in this thesis suggests that by growing existing Vicia faba lines with floral traits including purple flowers with more concentrated nectar, farmers can ensure better crop yield in environments where pollinators are present. In addition, floral traits should be considered as breeding targets by V. faba breeders, as they have great potential to increase crop pollination and support wild pollinator populations.