Wild bee visitation unaffected by disparate nectar phenotypes in a sunflower inbred line population

Authors: Prasifka, Jarrad; Fugate, Karen; Hulke, Brent

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2025
Publication Date: 6/11/2025
Citation: Prasifka, J.R., Fugate, K.K., Hulke, B.S. 2025. Wild bee visitation unaffected by disparate nectar phenotypes in a sunflower inbred line population. Crop Science. https://doi.org/10.1002/csc2.70093.
DOI: https://doi.org/10.1002/csc2.70093

Interpretive Summary: Within a plant species, types (or 'lines') that provide bees with more food (nectar and pollen), better quality food, or food that is easier to collect are likely to be preferred by bees. In this study, a large group of closely-related sunflower lines were used to test if differences in nectar caused wild bees to prefer specific lines. Nectars in almost all of the sunflower lines could be described as one of two types: high volume and low sucrose (one of three sugars in sunflower nectar) or low volume and high sucrose. Measurements on the lines showed plants of both nectar types were equally easy for bees to collect. Over two years, wild bee species common in sunflowers did not visit lines of either nectar type more, but bees did prefer some lines over others. It is not clear why bees did not prefer either nectar type, but several possible explanations are discussed.

Technical Abstract: Varition in the quality, quantity or accessibility of nectar and pollen within plant species is a potential target for plant breeding, both to enhance pollination and to support nutritional needs of pollinators. A biparental population of sunflower inbred lines that varied for nectar quantity and quality were used to determine whether nectar phenotypes influenced wild pollinator preference under field conditions in a primary North American sunflower production area. Under field conditions, nectar quality (% sucrose) was generally lower than in a controlled environment and % sucrose was inversely related to nectar volume. As a result, inbred lines generally fell into groups with disparate nectar phenotypes that were either high sucrose and low volume or low sucrose and high volume. Nectar accessibility, as measured by floret size, did not differ between the groups. Though pollinator visits to sunflower inbred lines varied ˜ three-fold and were correlated between years, analyses of covariance on pollinator observations did not show a significant effect of the two common nectar phenotypes in either of two years. Several non-mutually exclusive explanations for the lack of effect of nectar phenotype are plausible. Ongoing efforts to enhance sunflower pollination would benefit from additional work with the plant (revisit prior mapping, resolving trait correlations and potential trade-offs), pollinators (discovery of latent factors that may influence bee preference) and the effects of the environment on plant-pollinator interactions.