Abstract/Summary

The powdery mildews (Ascomycota, Erysiphales) are a group of obligate biotrophic fungi found on nearly 10,000 angiosperm plant hosts globally including many that are important horticultural and agricultural plants. Infection can greatly reduce the appearance and vigour of the host therefore reducing attractiveness and yields significantly. A reliable and efficient method is required for unambiguous identification of these often cryptic species such that spread to new areas and/or new hosts can be detected rapidly and controlled early. This research aims to combine currently accepted techniques – host identification, fungal morphological analysis, DNA sequencing of the fungal rDNA ITS region – with sequencing of additional nuclear DNA regions in order to increase the reliability of the identification process via BLAST, DNA Barcoding, and phylogenetic reconstruction. Samples were collected through the Powdery Mildew Survey (a citizen science scheme), begun in 2014 and concluded in 2016. Generic fungal DNA primers were found to amplify non-powdery mildew species, some of which were mycoparasites, as well as powdery mildews, and were therefore not a useful technique for accurate identification of powdery mildews. Consequently specific primers were developed for the amplification of the Actin, β-tubulin, Chitin synthase, Mcm7, Translation elongation factor 1-α, and Tsr1 regions. Results indicate that several of these regions could be used alongside ITS to increase identification power (reliability and accuracy), with regions Mcm7 and β-tubulin performing particularly well. These rapid diagnostic techniques could provide a valuable tool for plant quarantine, and plant breeding, particularly for greater security in the movement of plants and plant products in trade.