Lignin composition correlates with pod dehiscence in hairy vetch ( <i>Vicia villosa</i> Roth)

Abstract Farmers and policy makers are increasingly interested in cover cropping to remedy harms caused by annual cash crop systems. However, species used for cover cropping have limited breeding and improvement histories. The objective of this study was to examine seed pod lignin profiles in relation to pod dehiscence (shatter) in the semi‐domesticated legume hairy vetch ( Vicia villosa Roth). Sets of physiologically mature pod samples from V. villosa plants with high dehiscence and low dehiscence ( n = 18) were pooled, ground, and analyzed by pyrolysis coupled to gas chromatography–mass spectrometry. Across pods produced in two growing environments (2018–2019 in Corvallis, OR and Knox City, TX), high dehiscence plants had elevated content of guaiacyl lignin units (G; p &lt; 0.01, two‐sample t ‐test) and, concomitantly, reduced content of syringyl lignin units (S) ( p &lt; 0.01), leading to reduced lignin S:G ratios (in the range 0.51–0.86; p &lt; 0.01). In contrast, low dehiscence plants had pods with lower G lignin and more S‐lignin, resulting in higher lignin S:G ratios (up to 1.63). This large and consistent difference in lignin composition parallels physiological mechanisms reported in other domesticated legumes. It is suggested that the distinct lignin compositions in high‐ and low‐dehiscence pods may have a significant impact on their physical and mechanical properties, directly influencing the dehiscence process. Continued study of lignin profiles during hairy vetch pod development can improve selection for reduced pod dehiscence and improve the viability of hairy vetch as a cover crop.