DNA barcoding of Mycosphaerella species of quarantine importance to Europe

Abstract

The EU 7th Framework Program provided funds for Quarantine Barcoding of Life (QBOL) to develop a quick, reliable and accurate DNA barcode-based diagnostic tool for selected species on the European and Mediterranean Plant Protection Organization (EPPO) A1/A2 quarantine lists. Seven nuclear genomic loci were evaluated to determine those best suited for identifying species of Mycosphaerella and/or its associated anamorphs. These genes included β-tubulin (Btub), internal transcribed spacer regions of the nrDNA operon (ITS), 28S nrDNA (LSU), Actin (Act), Calmodulin (Cal), Translation elongation factor 1-alpha (EF-1α) and RNA polymerase II second largest subunit (RPB2). Loci were tested on their Kimura-2-parameter-based inter- and intraspecific variation, PCR amplification success rate and ability to distinguish between quarantine species and closely related taxa. Results showed that none of these loci was solely suited as a reliable barcoding locus for the tested fungi. A combination of a primary and secondary barcoding locus was found to compensate for individual weaknesses and provide reliable identification. A combination of ITS with either EF-1α or Btub was reliable as barcoding loci for EPPO A1/A2-listed Mycosphaerella species. Furthermore, Lecanosticta acicola was shown to represent a species complex, revealing two novel species described here, namely L. brevispora sp. nov. on Pinus sp. from Mexico and L. guatemalensis sp. nov. on Pinus oocarpa from Guatemala. Epitypes were also designated for L. acicola and L. longispora to resolve the genetic application of these names.