Bridging the Gap Between Platforms: Comparing Grape Phylloxera Daktulosphaira vitifoliae (Fitch) Microsatellite Allele Size and DNA Sequence Variation.

Grape phylloxera, Daktulosphaira vitifoliae (Fitch), is an economically significant pest of grapevines. Identification of phylloxera genotypes is an important aspect of management as genotypes differ in virulence and susceptibility to control using resistant rootstocks. Microsatellite markers developed on polyacrylamide gel systems have been the most widely used molecular method for phylloxera genotype identification, but this approach has been superseded by fluorescent capillary-based genotyping. The current study presents new laboratory methods for amplifying a standard set of eight phylloxera microsatellite markers using PCR-incorporated fluorescently labelled primers, genotyped on an ABI capillary platform. Comparison of allele size data scored on (i) polyacrylamide, (ii) capillary, and (iii) high-throughput sequencing (HTS) platforms revealed that the capillary genotyping most closely matched the HTS allele sizes, while alleles of loci originally scored on a polyacrylamide platform differ in size by up to three base pairs, mostly due to the presence of previously uncharacterised DNA sequence indels. Seven common clonal lineages of phylloxera known from Australia are proposed as reference samples for use in calibrating genotyping systems between platforms and laboratories to ensure universal scoring of allele sizes, providing a critical link for accurately matching previous phylloxera genotype studies with current research.