Surface-Enhanced Raman Scattering as a Complementary Molecular Analysis for Optical Seed-Vigor Phenotyping: A Critical Evidence Map and Validation-Boundary Analysis

Optical seed-vigor phenotyping enables rapid screening by near-infrared spectroscopy, hyperspectral imaging, Raman spectroscopy, and related methods. These measurements can predict seed performance without identifying the biochemical processes underlying a prediction. This narrative review examines how surface-enhanced Raman scattering (SERS) could add targeted molecular information to optical phenotyping. It distinguishes spontaneous Raman measurements, SERS biomarker assays, seed-matrix analytical validation, and biological outcome linkage. The proposed application uses extracts from representative seed subsets; its destructive character arises from sample preparation, whereas Raman and SERS measurements can be non-destructive under suitable conditions. Seed Raman studies already support useful classification and relative chemical measurements. Among the ten biomarker-sensor papers mapped here, however, none combines seed-matrix calibration and reference chemistry with matched vigor outcomes and independent lot testing. This finding is limited to the mapped corpus rather than to all published research. Protein adsorption, lipid-rich co-extractives, pigments, and substrate variability require crop-specific assessment before quantitative SERS results can be transferred between seed types. A feasible starting point is a small target panel, paired extract aliquots for SERS and reference analysis, and germination testing of matched seed subsets. Studies in other matrices guide this development but do not establish seed-vigor performance.