Re-Evaluation of the <i>Podosphaera tridactyla</i> Species Complex in Australia

• Main Authors: Reannon L. Smith, Tom W. May, Jatinder Kaur, Tim I. Sawbridge, Ross C. Mann, Ian G. Pascoe, Jacqueline Edwards
• Format: Article
• Language: English
• Published: MDPI AG 2021-02-01
• Series: Journal of Fungi
• Subjects: stone fruit; powdery mildew fungi; <i>Prunus</i>; <i>Podosphaera</i> <i>ampla</i>; <i>Podosphaera</i> <i>cunningtonii</i>
• Online Access: https://www.mdpi.com/2309-608X/7/3/171

The <i>Podosphaera tridactyla</i> species complex is highly variable morphologically and causes powdery mildew on a wide range of <i>Prunus</i> species, including stone fruit. A taxonomic revision of the <i>Po. tridactyla</i> species complex in 2020 identified 12 species, seven of which were newly characterised. In order to clarify which species of this complex are present in Australia, next generation sequencing was used to isolate the fungal ITS+28S and host <i>matK</i> chloroplast gene regions from 56 powdery mildew specimens of stone fruit and ornamental <i>Prunus</i> species accessioned as <i>Po. tridactyla </i>or <i>Oidium </i>sp. in Australian reference collections. The specimens were collected in Australia, Switzerland, Italy and Korea and were collected from 1953 to 2018. Host species were confirmed using <i>matK</i> phylogenetic analysis, which identified that four had been misidentified as <i>Prunus</i> but were actually <i>Malus</i><i>prunifolia</i>. <i>Podosphaera</i> species were identified using ITS+28S phylogenetic analysis, recognising three <i>Podosphaera </i>species on stone fruit and related ornamental <i>Prunus </i>hosts in Australia. These were <i>Po.</i><i>pannosa</i>, the rose powdery mildew, and two species in the <i>Po</i>. <i>tridactyla</i> species complex: <i>P</i>o. <i>ampla</i>, which was the predominant species, and a previously unidentified species from peach, which we describe here as <i>Po</i>. <i>cunningtonii.</i>