Development of a reverse transcription-loop- mediated isothermal amplification (LAMP) assay for the rapid detection of onion yellow dwarf virus

Onion yellow dwarf virus (OYDV) is one of the most important viral pathogens of onion. In particular, on ‘Rossadi Tropea’ onion, granted with Protected Geographical Indication (PGI) trademarks, this pathogen represents themost limiting biotic stress in terms of spread, severity of symptoms and damage, and its detection is necessary topreserve high quality standards and avoid yield losses. A reverse transcription-loop mediated isothermal amplification(RT-LAMP) assay was developed for detection of OYDV. The specificity, sensitivity, repeatability andreproducibility of the assay were validated according to EPPO standard PM7/98 (2). Diagnostic specificity,diagnostic sensitivity and diagnostic accuracy were determined in both leaf and bulb tissues. To enhance thefeasibility of a LAMP-based method for field diagnosis, several nucleic acid extraction methods were comparedto simplify sample preparation. The results showed the reliability of the method for OYDV detection, with a limitof detection (LOD) comparable to real time reverse transcription polymerase chain reaction (RT-qPCR). The easeof sample preparation, and the more than acceptable LOD, indicated that the RT-LAMP assay could be used inplant pathology laboratories with limited facilities and resources, as well as directly in the field. This work wascarried out in the frame of “SI.ORTO” project.