A diagnostic LAMP assay for the destructive grapevine insect pest, phylloxera (*Daktulosphaira vitifoliae*)

Grape phylloxera (Daktulosphaira vitifoliae) is a destructive insect pest of grapevines that is highly invasive worldwide, despite strict biosecurity containment measures in place at farm and regional levels. Current phylloxera identification by visual inspection and laboratory-based molecular methods is time-consuming and costly. More rapid and cost-effective methods for identification of this pest would benefit industry, growers, and biosecurity services. Loop mediated isothermal amplification (LAMP) is a new portable technology available for rapid and accurate in-field molecular diagnostics. This study outlines the development of a new LAMP assay to enable the identification of phylloxera specimens. New LAMP primers were developed to specifically amplify phylloxera mitochondrial DNA (5'-COI), which we have shown is effective as a DNA barcode for identification of phylloxera, using LAMP technology. Positive LAMP reactions, containing phylloxera DNA, amplified in less than twelve minutes with an anneal derivative temperature of approximately 79 °C to 80 °C compared to a newly designed synthetic DNA (gBlock) fragment which had an anneal derivative temperature of 82 °C. No LAMP amplification was detected in any of the non-target species tested, i.e. no false-positive identification resulted for these species. We also successfully optimised a non-destructive DNA extraction procedure, HotSHOT "HS6", for use in the field on phylloxera adults, nymphs and eggs, to retain physical specimens. DNA extracted using this method was also suitable for species and genotype molecular identification methods, such as DNA barcoding, qPCR and microsatellite genotyping. The new LAMP assay provides a novel visual molecular tool for accurate diagnostics of phylloxera in the laboratory and field.

Arati Agarwal, J. Paul Cunningham, Isabel Valenzuela, Mark J. Blacket