Pretoria, South Africa
Pretoria, South Africa

Time filter

Source Type

Bahramisharif A.,Stellenbosch University | Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Spies C.F.J.,Stellenbosch University | Spies C.F.J.,Agriculture and Agri Food Canada | And 2 more authors.
Mycologia | Year: 2013

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, b-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. © 2013 by The Mycological Society of America.


Spies C.F.J.,Stellenbosch University | Mazzola M.,U.S. Department of Agriculture | Botha W.J.,ARC PPRI | Van Der Rijst M.,ARC Biometry Unit | And 2 more authors.
Fungal Biology | Year: 2011

Pythium vexans fits into the internal transcribed spacer (ITS) clade K sensu Lévesque & De Cock (2004). Within clade K, P. vexans forms a distinct clade containing two enigmatic species, Pythium indigoferae and Pythium cucurbitacearum of which no ex-type strains are available. In South Africa, as well as in other regions of the world, P. vexans isolates are known to be heterogeneous in their ITS sequences and may consist of more than one species. This study aimed to investigate the diversity of South African P. vexans isolates, mainly from grapevines, but also citrus and apple using (i) phylogenetic analyses of the ITS, cytochrome c oxidase (cox) I, cox II, and β-tubulin regions and (ii) seven biometric oogonial parameters. Each of the phylogenies clustered P. vexans isolates into a single well-supported clade, distinct from other clade K species. The β-tubulin region was phylogenetically uninformative regarding the P. vexans group. The ITS phylogeny and combined cox I and II phylogenies, although each revealing several P. vexans subclades, were incongruent. One of the most striking incongruences was the presence of one cox subclade that contained two distinct ITS subclades (Ib and IV). Three groups (A-C) were subjectively identified among South African P. vexans isolates using (i) phylogenetic clades (ITS and cox), (ii) univariate analysis of oogonial diameters, and (iii) multivariate analyses of biometric oogonial parameters. Group A is considered to be P. vexans s. str. since it contained the P. vexans CBS reference strain from Van der Plaats-Niterink (1981). This group had significantly smaller oogonial diameters than group B and C isolates. Group B contained the isolates from ITS subclades Ib and IV, which formed a single cox subclade. The ITS subclade IV isolates were all sexually sterile or produced mainly abortive oospores, as opposed to the sexually fertile subclade Ib isolates, and may thus represent a distinct assemblage within group B. Although ITS subclade Ib included the P. indigoferae ex-type sequence, this group was considered to be P. vexans since South African isolates in this clade produced globose sporangia. Group C contained four apple isolates that were related to, but distinct from P. cucurbitacearum. Although P. vexans groups A-C might be distinct species, they are not described here as such due to (i) these groups only representing some of the known diversity in P. vexans, (ii) conflicting gene tree phylogenies preventing phylogenetic species identification, and (iii) sexually sterile isolates preventing the broad application of biometrical data. © 2010 The British Mycological Society.


Spies C.F.J.,Stellenbosch University | Mazzola M.,U.S. Department of Agriculture | Botha W.J.,ARC PPRI | Langenhoven S.D.,Stellenbosch University | And 2 more authors.
Fungal Biology | Year: 2011

The Pythium irregulare species complex is the most common and widespread Pythium spp. associated with grapevines in South Africa. This species complex has been subdivided into several morphological and phylogenetic species that are all highly similar at the sequence level [internal transcribed spacer (ITS) and cytochrome c oxidase (cox) regions]. The complex includes Pythium regulare and Pythium cylindrosporum, which are morphologically distinct, and P. irregulare sensu stricto (s.s.) and Pythium cryptoirregulare, which are morphologically similar. The aim of the current study was to determine whether 50 South African grapevine P. irregulare isolates represented more than one phylogenetically distinct species. The isolates were characterised using nuclear (ITS and β-tubulin) and mitochondrial (cox1 and cox2) gene region phylogenies and two isozyme loci [glucose-6-phosphate isomerase (Gpi) and malate dehydrogenase (Mdh-1)]. Some of the gene sequence data were difficult to interpret phylogenetically, since some isolates contained two or more polymorphic ITS copies within the same isolate (intra-isolate variation) that clustered into different ITS sub-clades, i.e. the P. irregulare s.s. and P. cryptoirregulare sub-clades. The molecular data furthermore only revealed the presence of one phylogenetic species, P. irregulare. Morphological analyses of a subset of the isolates confirmed that the isolates were P. irregulare, and further showed that the P. cylindrosporum ex-type strain formed typical P. irregulare oogonia, and not the previously reported distinct elongated oogonia. Some of the molecular analyses suggested the occurrence of outcrossing events and possibly the formation of aneuploids or polyploids since (i) the nuclear and mitochondrial gene data sets were incongruent, (ii) polymorphic ITS copies were present within the same isolate, (iii) heterozygosities were observed in the β-tubulin gene and Gpi and Mdh-1 loci in some isolates and (iv) more than two β-tubulin alleles were detected in some isolates. Altogether, the data suggest that P. irregulare, P. cryptoirregulare, P. cylindrosporum, and possibly P. regulare should be synonimised under the name P. irregulare. © 2011 The British Mycological Society.


Dowling A.P.G.,University of Arkansas | Ochoa R.,U.S. Department of Agriculture | Beard J.J.,University of Maryland University College | Ueckermann E.A.,ARC PPRI
Experimental and Applied Acarology | Year: 2012

The genus Raoiella is best known because of the red palm mite, R. indica, a major pest of palms spreading aggressively throughout the Americas. Not much was known about the biology, geographic origins, or evolutionary history of the genus when R. indica emerged as a major invasive pest. This paper attempts to address some of the basic historical questions regarding the palm mite as well as the genus. Molecular characters from COI and 28S regions were used to produce a phylogenetic hypothesis for the genus in an effort to understand its geographic origin. It also uses COI barcode data to delimit several potentially new species discovered by the authors in Australia. Results show a basal split between R. indica and all other Raoiella species, which indicates Africa or the Middle East as the most probable origin of the genus. Additionally, COI data suggests that at least eight new species are represented among the 20 Australian populations included in this study. © 2011 Springer Science+Business Media B.V. (outside the USA).


Bahramisharif A.,Stellenbosch University | Lamprecht S.C.,Agricultural Research Council Plant Protection Research Institute | Spies C.F.J.,Stellenbosch University | Botha W.J.,ARC PPRI. | And 2 more authors.
Plant Disease | Year: 2014

Rooibos (Aspalathus linearis) is an important indigenous crop in South Africa. Oomycetes are a common problem in rooibos nurseries, causing serious losses, but limited information is available on the species involved. Molecular and morphological analyses of 117 oomycete isolates from 19 rooibos nurseries and 33 isolates from 11 native rooibos sites revealed the presence of several Pythium spp., including Pythium acanthicum, P. irregulare, P. mamillatum, P. myriotylum, P. pyrilobum, P. cederbergense, and Pythium RB II, and Phytophthora cinnamomi (native site). Most of the species were identified in nurseries and native rooibos, with Pythium irregulare being the most common species occurring in all nurseries and 46% of the native sites. Phylogenetic analyses of the internal transcribed spacer region of the P. irregulare isolates showed that isolates within this species complex fit into three subclades, of which only two have previously been reported.On rooibos, all species except P.acanthicum and the previously characterized P. cederbergense and Pythium RB II were pathogenic and highly virulent. On lupin and oat, rotation crops in nurseries, the three aforementioned species were also nonpathogenic. All the other oomycete species were pathogenic on lupin but less so than on rooibos. On oat, only P. irregulare, P. myriotylum, and P. pyrilobum were pathogenic. This is the first report of P. mamillatum, P. pyrilobum, and P.myriotylum as pathogens of lupin, and P. irregulare and P. pyrilobum as pathogens of oat. The three nonpathogenic Pythium spp. were able to significantly reduce disease caused by pathogenic species in the less susceptible lupin and oat but not on rooibos. On lupin, the nonpathogenicspecies enhanced the virulence of Phytophthora cinnamomi. © 2014 The American Phytopathological Society.


Bagheri M.,Islamic Azad University at Maragheh | Mohajer S.S.,Gorgan University of Agricultural Sciences and Natural Resources | Saboori A.,University of Tehran | Asadeh G.,Gorgan University of Agricultural Sciences and Natural Resources | And 2 more authors.
Acarologia | Year: 2011

A new species of Storchia Oudemans (Acari: Stigmaeidae) is described and illustrated based on specimens collected from moss and soil in Golestan Province, Iran. A key to all species of Storchia (female) is also provided.


Akyazi R.,Ordu University | Ueckermann E.A.,ARC PPRI | Ueckermann E.A.,North West University South Africa | Soysal M.,Ordu University
Acarologia | Year: 2016

Amblyseius herbicolus Chant, 1959 (Mesostigmata: Phytoseiidae) is reported for the first time in Ordu province (Sea side, Black Sea Region), Turkey. The specimens were collected from persimmon trees (Diospyros kaki Thunb., Diospyros lotus L.) infested with tenuipalpid and tydeid mites in Altınordu and Perşembe, Ordu Province, Turkey. © Akyazi R. et al.


Bagheri M.,Islamic Azad University at Maragheh | Bonab R.N.,North West University South Africa | Bonab R.N.,Islamic Azad University | Ueckermann E.A.,ARC PPRI | And 3 more authors.
Systematic and Applied Acarology | Year: 2011

A new species of Stigmaeus Koch (Acari: Stigmaeidae), Stigmaeus marandiensis sp. nov. is described and illustrated from soil in apple orchards at Marand, East Azerbaijan Province, Iran. A key to all known species from Iran of the genus Stigmaeus is also provided. © 2011 Systematic & Applied Acarology Society.


Bagheri M.,Islamic Azad University at Maragheh | Ghorbani H.,Islamic Azad University at Maragheh | Ueckermann E.A.,ARC PPRI | Ueckermann E.A.,North West University South Africa | And 3 more authors.
International Journal of Acarology | Year: 2012

A new species of Stigmaeus Koch (Acari: Stigmaeidae), Stigmaeus maraghehiensis sp. nov., is described and illustrated from the soil in apple orchards in Maragheh, East Azerbaijan Province, Iran. A key to all known Iranian species of the genus is provided. © 2012 Copyright Taylor and Francis Group, LLC.


Tecoma stans var. stans, a tree originating from the Americas, is emerging as an invasive weed in South Africa. A microcyclic gall inducing rust fungus, Prospodium transformans, has been investigated as a biological control agent against this plant. Development of germinating teliospores and symptoms on host plants are described, and the optimum temperature for teliospore germination was found to be 18-22°C. Inoculations of plants grown from seed originating from South Africa and various localities in Mexico and Texas (USA) indicate that there are likely races specific to morphological variants of this widespread and highly variable plant species. Despite readily inducing galls on plants grown under quarantine glasshouse conditions in South Africa, this rust fungus failed to establish in the field upon release. It is suggested that the origin of the form of this plant, which has become invasive in South Africa, needs to be identified to source the correct race of P. transformans for release in South Africa. © Brazilian Phytopathological Society.

Loading ARC PPRI collaborators
Loading ARC PPRI collaborators