Pythium cederbergensesp. nov. and related taxa fromPythiumclade G associated with the South African indigenous plantAspalathus linearis(rooibos)

Abstract

The genus Pythium consists of more than 120 species and is subdivided into 11 phylogenetic clades (A-K) based on internal transcribed spacer (ITS) region sequence data. Pythium clade G contains only seven known species, with most not being well described. Our study characterized 12 Pythium isolates from Aspalathus linearis (rooibos) that fit into clade G. Phylogenetic analyses of the ITS region and a combined phylogeny of four gene regions (ITS, β-tubulin, COX1 and COX2 [cytochrome c oxidase subunits I, II]) identified five clade G subclades. The rooibos isolates formed two groups, Pythium Rooibos I (RB I) and II (RB II), that clustered into two separate clades within subclade 1. The nine Pythium RB I isolates formed a distinct clade from P. iwayamai and is described here as a new species, Pythium cederbergense sp. nov. The three Pythium RB II isolates had P. canariense and P. violae as their closest relatives and were genetically diverse, suggesting the presence of several new species or a species complex that cannot be resolved with the current data, thus precluding a species description of this group. Morphological analyses showed that P. cederbergense and Pythium RB II were indistinguishable from each other but distinct from known clade G species. Clade G studies are being hampered by imprecise morphological descriptions of P. violae, P. canariense and P. iwayamai and each species being represented by only one isolate. The P. cederbergense and Pythium RB II isolates all were nonpathogenic toward rooibos, lupin and oats seedlings. One oligonucleotide was developed for each of P. cederbergense and Pythium RB II, which was able to differentiate the isolates with DNA macro-array analyses.

One stop shop: backbones trees for important phytopathogenic genera: I (2014)

“…21 (data not shown) and has limited power in resolving species-level phylogenies (Spies et al 2011a, b), it amplifies and sequences well for most Pythium species and is an easy resource for use in concatenated datasets (e.g. Bahramisharif et al 2013;Fig. 21).…”

“…Some species epithets have been applied to multiple phylogenetic species due to imprecise species descriptions and/or misidentifications. Examples of these include P. iwayamai, P. okanoganense and P. violae (Lévesque and de Cock 2004;McLeod et al 2009;Bahramisharif et al 2013). Mislabelling or contamination of reference strains and/or data cause similar problems, as illustrated by the case of P. terrestre (published as "terrestris") of which the holotype strain ITS sequence published with the description suggests phylogenetic placement in clade E (Paul 2002), while the ITS and cox1 sequences generated for the ex-type strain available from the Centraal Bureau voor Schimmelcultures (CBS) suggests phylogenetic placement in clade F (Robideau et al 2011).…”

Globisporangium coniferarum sp. nov ., associated with conifers and Quercus spp.

“…Globisporangium cederbergense does not produce zoospores ( Bahramisharif et al 2013 ). However, production of terminal and globose hyphal swellings, terminal, or intercalary oospores with up to two monoclinous antheridia has been reported in this species ( Bahramisharif et al 2013 ).…”

“…Globisporangium cederbergense does not produce zoospores ( Bahramisharif et al 2013 ). However, production of terminal and globose hyphal swellings, terminal, or intercalary oospores with up to two monoclinous antheridia has been reported in this species ( Bahramisharif et al 2013 ). Furthermore, terminal to intercalary hyphal swellings, clavate antheridia, and both mono- and diclinous antheridia were observed in G. coniferarum .…”

“…Furthermore, terminal to intercalary hyphal swellings, clavate antheridia, and both mono- and diclinous antheridia were observed in G. coniferarum . Additionally, G. cederbergense is known to produce only aplerotic oospores ( Bahramisharif et al 2013 ), whereas G. coniferarum produces both plerotic and aplerotic oospores. Minimum temperature for growth in G. cederbergense is 3 to 5 °C, whereas G. coniferarum could not tolerate temperatures below 15 °C .…”