Baobabopsis, a new genus of graminicolous downy mildews from tropical Australia, with an updated key to the genera of downy mildews.

Marco Thines,Young-Joon Choi,Yu Pei Tan,Roger G Shivas,Sabine Telle

doi:10.5598/imafungus.2015.06.02.12

Abstract

So far 19 genera of downy mildews have been described, of which seven are parasitic to grasses. Here, we introduce a new genus, Baobabopsis, to accommodate two distinctive downy mildews, B. donbarrettii sp. nov., collected on Perotis rara in northern Australia, and B. enneapogonis sp. nov., collected on Enneapogon spp. in western and central Australia. Baobabopsis donbarrettii produced both oospores and sporangiospores that are morphologically distinct from other downy mildews on grasses. Molecular phylogenetic analyses showed that the two species of Baobabopsis occupied an isolated position among the known genera of graminicolous downy mildews. The importance of the Poaceae for the evolution of downy mildews is highlighted by the observation that more than a third of the known genera of downy mildews occur on grasses, while more than 90 % of the known species of downy mildews infect eudicots.

Highlights

Graminicolous downy mildews (GDM) occur on diverse wild and cultivated grasses, in the semi-arid tropics and subtropics
Several unusual and unidenti ed downy mildews have been collected on native Australian tropical grasses, in particular on species of Perotis and Enneapogon that extend into New Guinea and Malesia (Simon & Alfonso 2011)
The aims of this study were to identify the downy mildews on specimens of Perotis and Enneapogon in BRIP (Plant Pathology Herbarium, Brisbane), and further, to investigate their phylogenetic relationships with other GDM

Summary

Introduction

Graminicolous downy mildews (GDM) occur on diverse wild and cultivated grasses, in the semi-arid tropics and subtropics. Seven genera of GDM, namely, Eraphthora (Telle & Thines 2012), Graminivora (Thines et al 2006), Peronosclerospora (Shirai & Hara 1927), Poakatesthia (Thines et al 2007), Sclerophthora (Thirumalachar et al 1953), Sclerospora (Schröter 1886), and Viennotia (Göker et al 2003), have been described to date. Three of these genera, Peronosclerospora, Sclerophthora, and Sclerospora, cause signi cant and widespread economic losses (Kenneth 1981, Jeger et al 1998, Spencer & Dick 2002). The aims of this study were to identify the downy mildews on specimens of Perotis and Enneapogon in BRIP (Plant Pathology Herbarium, Brisbane), and further, to investigate their phylogenetic relationships with other GDM

Objectives

Methods

Results

Conclusion