Foliar infrared spectra track nematode density and symptom-specific phytobiome signatures in beech leaf disease

Beech leaf disease (BLD), caused by the foliar nematode Litylenchus crenatae ssp. mccannii (LCM) is an emerging threat to American beech (Fagus grandifolia) across eastern North America. In this study, near-infrared (NIR) spectroscopy was integrated with microbiome sequencing and machine learning approaches to evaluate whether host spectral signatures can predict pathogen abundance and associated phytobiome composition. Spectral profiles were analyzed using multivariate statistical approaches and predictive models, including random forest, support vector machines, elastic net regression, and partial least squares regression. NIR spectra accurately predicted nematode abundance and reconstructed major gradients of bacterial community differentiation derived from 16S rRNA gene sequencing, with nonlinear models exhibiting the highest predictive performance. These results indicate that host spectral signatures encode biochemical information reflecting both pathogen burden and microbiome stru..., , # Foliar infrared spectra track nematode density and symptom-specific phytobiome signatures in beech leaf disease

Dataset DOI: [10.5061/dryad.m37pvmdgv](https://doi.org/10.5061/dryad.m37pvmdgv)

## Description of the data and file structure

**Spectral data:** Near-infrared (NIR) reflectance spectra (1350–2550 nm; 257 bands) collected from American beech leaves representing three tissue phenotypes associated with beech leaf disease: asymptomatic tissue of asymptomatic leaves (AA), asymptomatic tissue of symptomatic leaves (AS), and symptomatic galled tissue (GS). Spectra were acquired using a handheld NeoSpectra spectrometer and processed to remove outliers and underwent a second derivative transformation. 

**qPCR quantification:** Litylenchus crenatae ssp. mccannii abundance was quantified using a probe-based qPCR assay targeting the FAR region with nematode-spiked standard curves. DNA samples were diluted prior to analysis and quantified in triplicate reactions for nematode density ..., ,