Conserved Accession–Lot Geometry but Limited Individual Spectral Retrieval: Bidirectional Transfer Across Two Hyperspectral Imaging Systems

Cross-system portability of hyperspectral seed classifiers was evaluated using paired Headwall and AisaFENIX spectra from 3200 seeds representing 32 grain-legume accession–lots. The same seeds retained their positions and orientation during same-day acquisitions. Spectra were smoothed on their native axes and interpolated over 450–950 nm at 5 nm intervals. Accession-distance correlations after within-sensor wavelength standardisation were 0.958–0.996. In a separate within-accession diagnostic, correlation-based individual retrieval accuracy was 0.81–1.44% against a 1% random benchmark. Across 30 overlapping pair-preserving splits, direct-transfer principal component analysis–linear discriminant analysis (PCA–LDA) macro-F1 ranged from 0.367 to 0.646. Piecewise direct standardisation (PDS) and correlation alignment (CORAL) improved performance in all 12 fixed-split comparisons with direct transfer, with paired-bootstrap intervals excluding zero. Full-grid ridge direct standardisation (DS) achieved higher mean macro-F1 than both in all six representation–direction combinations. Within-accession calibration-pair derangement had small, setting-dependent effects, whereas accession mismatching strongly reduced PDS performance. Low-budget CORAL benefited from accession-balanced target sampling. These results demonstrate conserved relative accession–lot structure and calibration-dependent PCA–LDA transfer within the studied population. Validation across new lots, acquisition days and instrument units would extend their generality.