Submitted to: Great Lakes Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pennycress is a new oilseed crop for the Midwestern USA. When blooming, pennycress flowers serve as important source of food (pollen and nectar) for pollinators. Pollinator visitation has been studied in wild-type pennycress. Recently, new commercial varieties of pennycress have been developed that have distinctly yellow seed, different than the black seed color of wild genotypes. The difference in seed color is due to biochemicals that can be translocated to flowers, which could make them more, or less, attractive to pollinators. Over two growing seasons at two locations in Illinois and two in Minnesota, we evaluated pollinator preference for yellow-seeded versus black-seeded pennycress varieties and determine flower densities and timing of flowering for the two varieties. Both varieties flower at similar times and produced comparable numbers of open flowers. In three of the nine site-years of the study, black-seeded pennycress accumulated more flowers over the course of flowering than the yellow-seeded variety. Generally, pollinating insects, mostly flies and thrips (small, winged insect), showed no preference for either pennycress variety, although occasionally, flies did prefer the black-seed pennycress flowers. Results indicate that genetic selection for yellow-coated pennycress seeds will have little impact on flower attractiveness to most pollinators. Results will benefit scientists, industry, and producers working to develop pennycress as a commercial crop.

Technical Abstract: Pennycress is being developed in the Midwestern USA as a new oilseed crop that provides numerous ecosystem services. These services include being an early spring source of pollen and nectar for pollinating insects. Most past research on pennycress pollinators used wild genotypes of pennycress. All wild genotypes have seed coats that are black, which occurs because of high levels of proanthocyanadins (PACs). Concentrations of PACs are minimal in newly developed genotypes with yellow-colored seed coats. However, little is known regarding flower abundance and timing nor insect preferences for black-seeded or yellow-seeded pennycress. Flower densities were recorded and pan traps were deployed weekly during pennycress flowering at nine site-years in Illinois and Minnesota to examine anthesis and insect preferences for black-seeded vs. yellow-seeded pennycress. Black- and yellow-seeded pennycress flowered simultaneously, responded similarly to post-sowing growing degree days (peaking at 700 GDD4°C), and produced comparable numbers of open flowers (up to 10,000 m-2) on any given day, although black-seeded pennycress produced significantly greater numbers of cumulative flowers over the course of anthesis in three of nine site-years. Overall, about 92% of trapped insects were comprised of Diptera (flies), Thysanoptera (thrips), and Hymenoptera (bees), and just 8% included Coleoptera (beetles), Hemiptera (true bugs) and Lepidoptera (butterflies). Generally, there were no significant differences in the relative frequencies of pollinator types found in yellow- versus black-seeded pennycress across site-years. Occasionally, however, black-seeded pennycress was preferred, which mainly was driven by insects in the order Diptera. These results suggest that genetic selections for yellow seed coats (with low PACs) will have little impact on flower attractiveness to most pollinators.