Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2024
Publication Date: 1/31/2025
Citation: Tilhou, N.W., Kucek, L.K., Moore, V., Hanson, S., Reberg-Horton, C., Ryan, M., Ehlke, N., Bartrow, A., Carr, B., Douglas, J., Englert, J., Woodard, A., Crawford, J., Raasch, J.A., Crawford, R., Ali, S., Bhamidimarri, S., Mirsky, S.B., Monteros, M., Moore, G., Gamble, A., Rajan, N., Narayanan, S., Haramoto, E., Basinger, N.T., Sykes, V., Mcwhirt, A., Reiter, M., Riday, H. 2025. Hairy vetch (Vicia villosa Roth) germplasm contains a cryptic second species (Vicia varia host). Crop Science. https://doi.org/10.1002/csc2.21455.
DOI: https://doi.org/10.1002/csc2.21455

Interpretive Summary: Hairy vetch is a highly diverse cover crop which has been grown in the United States for over 100 years. During this time, researchers and farmers have noted many subpopulations of hairy vetch. Using evidence from field trials, modern genetic sequencing, and measurement of flower morphology, this paper provides evidence that hairy veth (Vicia villosa Roth) germplasm contains a second species that we call smooth vetch (Vicia varia Host). Incidentally, this research also determined that wollypod vetch (Vicia dasycarpa Ten.) is a subpopulation within hairy vetch and is not a distinct species. This information is important for researchers and farmers becasue these species have different preferred growing regions. Smooth vetch has superior performance in the southeastern U.S. and Pacific northwest U.S. Hairy vetch has superior performance in the north-central U.S.

Technical Abstract: Hairy vetch is a promising legume cover crop (Vicia villosa Roth) for the northern United States. Based on evidence from molecular markers, multi-site evaluations, and morphological observations, a distinct second species exists within U.S. hairy vetch germplasm. We will refer to it as smooth vetch (Vicia varia Host). Morphologically, hairy vetch is highly variable, but this study found statistically significant differences between smooth and hairy vetch in visual pubescence scores, plant maturity, and calyx lobe lengths. We used a panel of single sequence repeat (SSR) markers to assign cultivars and breeding materials to the two species and found that many commercial cultivars are smooth vetch. Interestingly, the SSR panel indicated that woollypod vetch (Vicia dasycarpa Ten.) is a subpopulation of hairy vetch. Based on an elastic net model trained with multi-site trial results from > 35 site-years, smooth vetch is not winter hardy in the northern U.S. but has superior performance relative to hairy vetch in the south-central and Pacific northwest United States. Specifically, smooth vetch has greater performance in environments with mild winters, cool spring temperatures, high sand, or low clay soils. Because of these differences in adaptation, differentiating these species will greatly improve agronomic outcomes and accelerate ongoing cover crop breeding progress.