ITS region of the rDNA of Pythium longandrum, a new species; its taxonomy and its comparison with related species

Pythium longandrum (F-73.0) was isolated, from soil samples taken in Lille in northern France. Morphologically the fungus resembles closely Pythium rostratum, however its antheridial characters are unique. The oogonia of this species are provided with hypogynous and monoclinous antheridia. The antheridial cells are inflated and are probably the largest and longest for the genus. The internal transcribed spacer region of its nuclear ribosomal DNA indicates that it is entirely different from all other species of Pythium. This new species is characterized by its spherical to elongated sporangia, smooth-walled oogonia and hypogynous to monoclinous antheridia bearing long antheridial cells closely applied to the oogonia. Morphological features of this new species, together with the sequences of the ITS region of its nuclear ribosomal DNA and comparison with related species are discussed here.     

Pythium ornacarpum: a new species with ornamented oogonia isolated from soil in France

Pythium ornacarpum sp. nov. was isolated from a soil sample taken from Genlis in the Burgundy region of France. This species is unique because of its ornamented oogonia which are completely surrounded by antheridial filaments. The fungus is closely related to Pythium echinulatum Matthews. Morphological and reproductive aspects of this species as well as a study by PCR of the sequence of the internal transcribed spacer (ITS1) of the nuclear ribosomal gene and its comparison with related species are described here. The nucleotide sequence of the ITS1 region flaking the 5.8S rRNA of this species and other related species are also given here.     

ITS1 region of the rDNA of Pythium proliferatum, a new species: its taxonomy and its comparison with related species

A new species, Pythium proliferatum (F-382), was isolated from soil samples taken in Genlis in the burgundian region of France. The fungus is unique because of the character combinations of its large, spherical to elongated, proliferating sporangia, and its smooth walled oogonia supplied with different types of antheridia like hypogynous, monoclinous sessile, monoclinous stalked, diclinous and wrapping around the oogonia. Almost all types of antheridia that are found in the genus are present in this new species. Morphological features of this new species, together with the sequences of the ITS1 region of its nuclear ribosomal DNA and its comparison with related species are discussed in this article.     

分离自蔬菜地的腐霉一新种及其rDNAITS序列分析(英文)

从广西南宁收集的蔬菜地土壤样本中,分离得到一个新的腐霉种,命名为广西腐霉Pythium guangxiense。不同于其近似种,广西腐霉的孢子囊球形或亚球形;藏卵器球形、亚球形、椭圆形或囊形;雄器同丝生或异丝生,柄常分枝且缠绕藏卵器。对构成广西腐霉rDNAITS区段的772个碱基进行扩增和测序。在根据ITS序列建立的分子系统发育树中,广西腐霉与禾生腐霉Pythium graminicola、周雄腐霉P.periilum和肿囊腐霉P.inflatum等产生瓣状孢子囊的腐霉种关系密切。对广西腐霉进行了分类描述和其与近似种的比较。     

Molecular analyses of Pythium irregulare isolates from grapevines in South Africa suggest a single variable species

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.     

PYTHIUM SYLVATICUM鉴定及其专一性PCR引物

从杭州采集的水稻、棉花和大豆猝倒苗中分离到国内新记录腐霉种Pythium sylvaticum。该腐霉为异宗配合种,菌丝膨大体球形或柠檬形,雄器异丝生,藏卵器光滑,每个藏卵器上1~3个雄器,雄器常在接近藏卵器处形成二叉状分枝,卵孢子不满器。测定了该种4 个菌株的核糖体内转录间隔区(ITS)的序列,根据与59种腐霉ITS序列的比较,设计了P. sylvaticum种专一性引物PSF1和PSR2。实际结果表明:该引物能从11种共14株腐霉DNA中特异性地扩增P. sylvaticum,从而与其它10种腐霉区分。     

Pythium carbonicum,a new species isolated from a spoil heap in northern France,the ITS region,taxonomy and comparison with related species

Pythium carbonicum (F-72) sp. nov. was found in soil samples taken on the top of a spoil heap in northern France. The morphology of this new species resembles that of a recently described species: Pythium megacarpum. However, the antheridial and oogonial characteristics of this new species are unique, and the comparison of its ITS region of the nuclear ribosomal DNA indicates that this species is also related to the genus Phytophthora. The fungus does not sporulate, the sporangia germinate directly into mycelium through germ tubes. The oogonia of P. carbonicum are smooth-walled and also papillated, and are provided with monoclinous and diclinous antheridia that wrap around, forming a complicated knot. Morphological features of this new species, together with the sequences of the ITS region of its nuclear ribosomal DNA and its comparison with related species are discussed here.     

Pythium contiguanum nomen novum (syn. Pythium dreschleri Paul), its antagonism to Botrytis cinerea, ITS1 region of its nuclear ribosomal DNA, and its comparison with related species

Pythium drechsleri Paul was described as a new species from soil samples taken in a salt-marsh of Arzew, Algeria [Paul, B. (1988) Une nouvelle espèce de Pythium isolée d'une saline de l'ouest Algérien. Cryptogam. Mycol. 9, 325-333]. The name of the fungus, P. drechsleri, is a nomen invalidum, as it is a later homonym of P. drechsleri Rajgopalan and Ramakrishnan [Rajagopalan, S. and Ramakrishnan, K. (1971) Phycomycetes in agricultural soils with special reference to the Pythiaceae. Madras Univ. J. Sect. B 37,38, 100-117]. A new name, Pythium contiguanum is now being given to P. drechsleri Paul. This species is characterised by its contiguous inflated type of sporangia, smooth-walled oogonia and mostly monoclinous antheridia. Although the fungus is not known to be a pathogen, it has a very well developed appressorial system comprised of both sickle shaped and coiled appressoria. Morphological features, its antagonism towards the grape-vine pathogen Botrytis cinerea, together with the sequences of the ITS1 region of its nuclear ribosomal DNA and its comparison with related species are given here.     

Two new species,Pythium agreste and P. wuhanense,based on morphological characteristics and DNA sequence data

In an investigation of Pythium species in China, two new species, P. agreste and P. wuhanense, were identified based on morphological characteristics and DNA sequence data. Pythium agreste has slightly inflated sporangia, oogonia encompassed by antheridia and antheridial stalks forming a very complicated knot, and plerotic oospores. It differs from the morphologically similar P. volutum which has inflated sporangia, bigger oogonia, and aplerotic oospores; from P. kashmirense which has contiguous inflated sporangia, catenulate oogonia and coiled or bent oogonial stalks; and from P. pectinolyticum which has catenulate oogonia and bigger oogonia and oospores. Pythium wuhanense can be differentiated from morphologically similar P. emineosum and P. paroecandrum by its possession of intercalary cylindrical to elongated sporangia and intercalary oogonia catenulate with sporangia and antheridia. Phylogenetic analyses showed that these two new species were clearly separated from morphologically similar Pythium species, based on the internal transcribed spacer (ITS) region and cytochrome C oxidase subunit I (COI) gene sequences using maximum parsimony and Bayesian methods. The two new species are described and illustrated in detail.     

Pythium burgundicum sp. nov. isolated from soil samples taken in French vineyards

During the course of investigation on pythiaceous fungi occurring in the Burgundian vineyards, a new species of Pythium has been isolated. This oomycete is characterized by its nonproliferating and nonsporulating, spherical to cylindrical type of sporangia (hyphal bodies) germinating through germ tubes, smooth-walled oogonia that are supplied with hypogynous, monoclinous or rarely diclinous antheridia, and smooth-walled oospores. The antheridial cells are very prominent and are reminiscent of Pythium bifurcatum, Pythium segnitium and Pythium longandrum described previously by the author. The internal transcribed spacer region of the rRNA of this new species is composed of 883 bases, which is quite different from that of the closest relatives. Morphological and molecular features of this new species, named as Pythium burgundicum , are discussed in this article.