Development of a Field-Deployable Loop-Mediated Isothermal Amplification Assay for the Rapid Detection of Erysiphe corylacearum in Hazelnut

<i>Erysiphe corylacearum</i>, the causal agent of powdery mildew in hazelnut (<i>Corylus avellana</i> L.), has become an emerging pathogen of concern in Italian hazelnut production requiring rapid and accurate detection to support timely disease management and phytosanitary measures. We developed and validated a field-deployable loop-mediated isothermal amplification (LAMP) assay for the specific detection of <i>E. corylacearum</i> and evaluated three primer sets targeting the Internal Transcribed Spacer (ITS) region, RNA polymerase II second largest subunit <i>(rpb2</i>), and glutamine synthetase (<i>GS</i>) genes; the <i>GS</i>-targeting Ecg set showed the highest sensitivity and specificity. The assay was shown to be sensitive down to 200 fg of fungal DNA, efficiently detected <i>E. corylacearum</i> from diluted crude leaf extracts, and produced results within half an hour, allowing the detection of latent infections before visible symptoms emerged. On-site validation with a portable LAMP instrument showed the assay's suitability for field-deployable diagnosis and early-warning applications in hazelnut orchards.