Benefits of insect pollination to confection sunflowers differ across plant genotypes

Authors: Mallinger, Rachel; Prasifka, Jarrad

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2017
Publication Date: 10/13/2017
Citation: Mallinger, R.E., Prasifka, J.R. 2017. Benefits of insect pollination to confection sunflowers differ across plant genotypes. Crop Science. 57(6):3264-3272. https://doi.org/10.2135/cropsci2017.03.0148.
DOI: https://doi.org/10.2135/cropsci2017.03.0148

Interpretive Summary: Cultivated sunflowers have been bred for self-fertility, reducing the perceived need for animal pollinators that facilitate cross-pollination. However, selfing rates can vary across sunflower genotypes and environments resulting in variable pollinator needs. Most studies on sunflower pollination have been conducted in oilseed or hybrid seed production systems, with little available information on the pollination requirements of modern confection sunflowers. Our paper examined the benefits of insect pollination to 15 different confection hybrids (genotypes) over multiple years, comparing degrees of self-fertility, yield increases with pollinators, and relative attractiveness to pollinators. We found that pollinator benefits varied across hybrids with 5 of 15 showing significant yield increases that ranged from 39 – 108 %. Hybrids showing significant pollinator benefits generally had lower degrees of self-fertility and/or higher pollinator visitation rates than hybrids that did not receive significant pollinator benefits. Native wild bees, including specialists on sunflowers, were the most common pollinators visiting sunflowers. Our study demonstrates that the benefits of insect pollination vary among domesticated sunflower genotypes due in part to differing self-fertility and attractiveness to pollinators.

Technical Abstract: Sunflowers, Helianthus annuus L., are naturally self-infertile, requiring animal pollination to set seed. While domesticated sunflowers have been bred for self-fertility, reducing the need for pollinators, selfing rates vary across genotypes. The goal of this study was to evaluate the benefits of insect pollination to different confection sunflower hybrids. We conducted pollinator-exclusion experiments for 15 hybrids in 2014-2015, measuring self-fertility and yield increases with pollinators. To assess whether pollinator benefits differ across hybrids due to their relative attractiveness to pollinators, we compared bee visitation rates among hybrids and related these rates to seed mass. Overall, sunflower seed mass was 26% higher on open flowers compared to bagged ones. Furthermore, seed mass on open flowers increased significantly with pollinator visitation rates. Yield increases with insect-pollination differed among hybrids, though, with 5 of 15 showing significant increases ranging from 39 – 108%. Pollinator visitation rates and degrees of self-fertility also differed across hybrids, in part explaining the variability in pollinator benefits. Our study shows that pollinators increase confection sunflower yields, but benefits vary across hybrids due to their self-fertility and relative attractiveness to pollinators. Since native wild bees made the majority of pollinator visits, increases in their populations are most likely to positively impact sunflower yields.