Re-Evaluation of the Podosphaera tridactyla Species Complex in Australia.

Reannon L Smith,Jacqueline Edwards,Tom W May,Jatinder Kaur,Ian G Pascoe,Tim I Sawbridge,Ross C Mann

doi:10.3390/jof7030171

Reannon L Smith, Jacqueline Edwards + Show 5 more

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https://doi.org/10.3390/jof7030171

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Abstract

The Podosphaera tridactyla species complex is highly variable morphologically and causes powdery mildew on a wide range of Prunus species, including stone fruit. A taxonomic revision of the Po. tridactyla 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 matK chloroplast gene regions from 56 powdery mildew specimens of stone fruit and ornamental Prunus species accessioned as Po. tridactyla or Oidium 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 matK phylogenetic analysis, which identified that four had been misidentified as Prunus but were actually Malus prunifolia. Podosphaera species were identified using ITS+28S phylogenetic analysis, recognising three Podosphaera species on stone fruit and related ornamental Prunus hosts in Australia. These were Po. pannosa, the rose powdery mildew, and two species in the Po. tridactyla species complex: Po. ampla, which was the predominant species, and a previously unidentified species from peach, which we describe here as Po. cunningtonii.

Highlights

Published: 26 February 2021Stone fruit such as peaches (Prunus persica), cherries (Pr. avium), apricots (Pr. armeniaca), plums (Pr. domestica, Pr. salicina and Pr. cerasifera) and almonds (Pr. dulcis) belong to the genus Prunus (Rosaceae), which contains approximately 250 species distributed across temperate regions worldwide [1]
On the basis of phylogenetic analysis of multiple genes, the genus is subdivided into three subgenera: Cerasus, Padus and Prunus and the latter subgenus is further subdivided into seven sections: Amygdalus, Armeniaca, Emplectocladus, Microcerasus, Persicae, Prunocerasus and Prunus [3]
The objective of the current study was to clarify which species of the Po. tridactyla complex are present in Australia, utilising the generation sequencing (NGS) methods developed by Smith et al [12], based on a re-examination of powdery mildew collections from horticultural Prunus species and closely related ornamental Prunus species in Australia held in Australian plant pathogen reference collections

Summary

Introduction

Stone fruit such as peaches (Prunus persica), cherries (Pr. avium), apricots (Pr. armeniaca), plums (Pr. domestica, Pr. salicina and Pr. cerasifera) and almonds (Pr. dulcis) belong to the genus Prunus (Rosaceae), which contains approximately 250 species distributed across temperate regions worldwide [1]. On the basis of phylogenetic analysis of multiple genes, the genus is subdivided into three subgenera: Cerasus (cherries), Padus (bird cherries, including species formerly placed in Laurocerasus) and Prunus (plums) and the latter subgenus is further subdivided into seven sections: Amygdalus, Armeniaca, Emplectocladus, Microcerasus, Persicae, Prunocerasus and Prunus [3]. The Australian stone fruit industry was established in the late 1800s by European and Chinese settlers who introduced apricot, peach, nectarine and plums that were in Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations

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