Changes to architecture of Silphium integrifolium Michx. during domestication reveal new trade-offs for yield

Authors: Prasifka, Jarrad; PETERSON, KELSEY - University Of Minnesota; MALLINGER, RACHEL - University Of Florida; VAN TASSEL, DAVID - The Land Institute

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2022
Publication Date: 5/5/2022
Citation: Prasifka, J.R., Peterson, K., Mallinger, R.E., Van Tassel, D. 2022. Changes to architecture of Silphium integrifolium Michx. during domestication reveal new trade-offs for yield. Crop Science. 62:1060-1068. https://doi.org/10.1002/csc2.20737.
DOI: https://doi.org/10.1002/csc2.20737

Interpretive Summary: Silphium is a prairie plant being bred as a new oilseed and forage crop. To improve yields, scientists have considered breeding plants to have more seeds per head or fewer heads per plant (by having fewer branches). However, these changes to crop structure may cause unintended problems. When plants with greater numbers of seeds per head were grown, individual seeds were smaller, but the total weight of seed per head still increased. This result supports increasing the number of seeds per head. When some flower buds were removed to mimic the effects of breeding plants with fewer heads, individual seeds were bigger. But the improved seed size was not enough to make up for the loss of heads removed, suggesting that fewer heads (or fewer branches) may not improve yields for Silphium.

Technical Abstract: Ongoing domestication of wholeleaf rosinweed, Silphium integrifolium Michx., as a perennial oilseed and forage crop aims to improve yields while minimizing trade-offs. Two changes to plant architecture, feminization and reduced branching, have been considered for their potential to improve yields, but with limited understanding of potential trade-offs. Field tests with genets that vary for the number of pistillate ray florets per head (= feminization) failed to show that increasing the number of female florets per head had any effect on pollinator visitation and seed set (%), but revealed that feminization reduced embryo mass / achene. In general, tripling the number of ray florets per head reduced the mass of individual embryos by 50% or more, which suggests feminization still provides a net benefit for oil yields. Clipping (bud removal) used to simulate reduced branching in S. integrifolium affected components of yield in ways that were generally predictable; heads (receptacles) became larger and mass / achene increased. However, the large number of buds removed to achieve modest increases in head and achene size make reduced branching appear undesirable. Ultimately, S. integrifolium genets with genetically reduced branching are needed to make the best evaluation of this potential change. Both sets of experiments reveal plasticity in S. integrifolium yield components, and suggest that efforts to improve the quality of phenotypic data are important to efficient selection.