Polyphyly of intraspecific groups of <Emphasis Type="Italic">Umbelopsis ramanniana</Emphasis> and their genetic and morphological variation

The taxonomic positions of three intraspecific groups of Umbelopsis ramanniana in the genus Umbelopsis were analyzed based on the nucleotide sequences of their nuclear large subunit ribosomal DNA (nLSU rDNA) D1/D2 region. The examined members of the genus Umbelopsis were resolved into two major clades, Clades I and II. The intraspecific groups of U. ramanniana were nested within Clade II together with U. westeae, U. swartii, U. autotrophica, U. gibberisopra, U. angularis, and U. fusiformis. In this major clade, the intraspecific groups of U. ramanniana were split into three polyphyletic subclades. This suggests that U. ramanniana is an assemblage of several genetically distinct species. Interestingly, in spite of the diverse sporangiospore shapes of the members of Clade II, the genetic variation among them was small. It is considered that their flexible sporangia membranes make it possible for them to develop various sporangiospore shapes.     

Accelerated nrDNA evolution and profound AT bias in the medicinal fungus Cordyceps sinensis

Cordyceps sinensis is a reputed medicinal fungus growing parasitically on buried larvae of ghost moths in Asian high-altitude grassland ecosystems. We have analysed the intraspecific ITS nrDNA (ITS1, 5.8S gene, ITS2) variation among 71 sequences of C. sinensis available in EMBL/Genbank. The ITS sequences, submitted to Bayesian ML analyses, were distributed into five groups, referred to as A–E. Nine of the sequences (groups D and E) grouped with distantly related hypocrealean/clavicipitalean taxa and are interpreted as sequences erroneously accessioned under wrong taxon names. The remaining 62 sequences constituted three highly supported clades (groups A–C), that may represent cryptic (phylogenetic) species currently ascribed to C. sinensis. A remarkably high sequence divergence occurred in the 5.8S gene between the three groups. Sequences of groups B and C showed accelerated substitution rates and high AT nucleotide bias. We hypothesize that the accelerated evolution and AT bias have been caused by a shift in life historical attributes or ecology. We also suggest that the recorded differences in medicinal effects among C. sinensis populations may be attributed to the existence of genetically differentiated chemotypes in this morphotaxon.     

Identification and differentiation of mycorrhizal isolates of black alder by sequence analysis of the ITS region

 Twenty isolates of black alder ectomycorrhizas were characterized on the basis of internal transcribed spacer (ITS) DNA sequences and colony morphology in pure culture. The isolates were obtained from individual, surface-sterilized mycorrhizas morphologically identified as the mycorrhizal type "Alnirhiza cystidiobrunnea". Analysis of ITS sequences allowed differentiation into four groups; three were closely related, while one isolate (BEh-Uw1) was separated by high sequence dissimilarity within the ITS1 and ITS2 spacer regions. Culture morphology was not a satisfactory differentiating feature for these four groups. An Ncbi GenBank DNA database search revealed that isolates within the three closely related ITS groups displayed high homology to ITS sequences of Tomentella sublilacina and Thelephora terrestris, whereas BEh-Uw1 had the highest sequence similarity to an ITS DNA sequence of a basidiomycete DNA isolated from bamboo leaves. Accepted: 25 May 2000     

Genetic divergence and phylogenetic analysis of genus <Emphasis Type="Italic">Jatropha</Emphasis> based on nuclear ribosomal DNA ITS sequence

The genus Jatropha belongs to the family Euphorbiaceae having significant economic importance. The present investigation was undertaken with an aim to understand phylogenetic relationships among seven species (J. curcas, J. glandulifera, J. gossypifolia, J. integerrima, J. multifida, J. podagrica, and J. tanjorensis.) which are widely distributed in India, using nuclear ribosomal DNA ITS sequence (nrDNA ITS) and to compare the results with multilocus marker analysis systems reported earlier for the same genus. The size variation obtained among sequenced nrDNA ITS regions was narrow and ranged from 647 to 654 bp. The overall mean genetic distance (GD) of genus Jatropha was found to be 0.385. Highest interspecific GD (0.419) was found between J. glandulifera and J. multifida. The least interspecific GD (0.085) was found between J. gossypifolia and J. tanjorensis. The highest intraspecific GD was observed in J. podagrica (0.011) and least in J. gossypifolia (0.002). The phylogram obtained using nrDNA ITS sequence showed congruence with the phylograms obtained using multilocus markers system reported earlier with minor variations. The present study also strongly supports high phylogentic closeness of J. curcas and J. integerrima. The only exception found was J. podagrica which clustered with J. multifida in earlier based on multilocus marker analysis, was clustered with J. curcas in the present analysis. The sequence data generated in the present investigation will help for further studies in intraspecies population, and their phylogentic analysis, biogeographical, molecular evolution studies and also pave way for future phylogetic and/or evolution studies among the other groups belongs to the family Euphorbiaceae.     

Polyploid speciation inHedera (Araliaceae): Phylogenetic and biogeographic insights based on chromosome counts and ITS sequences

Variation in chromosome number and internal transcribed sequences (ITS) of nrDNA is used to infer phylogenetic relationships of a wide range ofHedera species. Polyploidy was found to be frequent inHedera, with diploid, tetraploid, hexaploid and octoploid populations being detected. Nucleotide additivity occurs in the ITS sequences of one tetraploid (H. hibernica) and two hexaploid species (H. maderensis, H. pastuchovii), suggesting that all three species originated by allopolyploidisation. ITS sequence polymorphism and nucleotide characters may indicate the presence of an ancient genome persistent only in some allopolyploid species. Phylogenetic analyses of ITS sequence data reveal two lineages ofHedera: one containing all sequences belonging to extant diploids plus the tetraploidH. algeriensis, and a second that includes this ancient ITS type and others exclusive to several polyploid species. The origin of the polyploids is evaluated on the basis of morphology, chromosome counts, ITS sequence polymorphism, and phylogenetic analyses. Reconstruction of reticulate evolution inHedera agrees with two allopolyploid areas on both sides of the Mediterranean basin. Morphological, molecular and cytological evidence also suggests an active dispersal ofHedera populations that may account for three independent introductions in Macaronesia.     

Restriction analysis of the amplified ribosomal DNA spacers ITS1 and ITS2 of <Emphasis Type="Italic">Bipolaris sorokiniana</Emphasis> isolates

The purpose of this study was to examine the genotypic variability of Bipolaris sorokiniana by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis using rDNA. Fifty B. sorokiniana isolates from Brazil and other countries, one Bipolaris oryzae and six Drechslera teres isolates were used. The intragenic spacer regions (ITS1 and ITS2) were the regions used for characterization of isolates. The amplification products for both ITS regions, showed two DNA fragments for all isolates. Two B. sorokiniana isolates presented an intraspecific variability showing a third fragment for the ITS1 region. The dendrograms generated with PCR-RFLP data showed intra- and inter-specific groups. The dendrograms showed that most of Brazilian isolates clustered together forming groups between them, and this behavior was repeated with most isolates from other countries. The dendrograms did not enable the separation of B. sorokiniana isolates by their geographic origin or host type. These results suggest the occurrence of gene flow between different populations of the fungus isolated in geographically distant regions and lends cogency to the occurrence of gene flow between species.     

Intra-isolate heterogeneity of the ITS region of rDNA in Pythium helicoides

Heterogeneity of the rDNA ITS region in Pythium helicoides and the phylogenetic relationship between P. helicoides and closely related species were investigated. In PCR-RFLP analysis of the rDNA ITS region of six P. helicoides isolates investigated, including the type culture, intraspecific variation was found at the HhaI site. The total length of fragments was longer than before cutting, indicating sequence heterogeneity within isolates. Digestion of the cloned rDNA ITS region derived from seven isolates with HhaI revealed polymorphisms among and within single zoospore isolates, and variability of the region was also present among the clones derived from the same isolate. To test whether the rDNA ITS region of closely related species and other regions in the genome of P. helicoides are also variable, the rDNA ITS region of P. ultimum and the cytochrome oxydase II (cox II) gene encoded in mitochondria were sequenced. P. ultimum had little variation in the rDNA ITS region. The cox II gene sequences of both species revealed only a low intraspecific variability and no intra-isolate variation. In the phylogenic tree based on the rDNA ITS sequences, all clones of P. helicoides formed one large clade that was distinct from the clades comprising morphologically similar species, such as P. oedochilum and P. ostracodes, and was closely related to P. chamaehyphon rather than the other species.     

四照花亚属的nrDNA ITS致同进化不完全

四照花亚属(Cornus subg.Syncarpea)隶属于山茱萸科山茱萸属(Cornus),我国该亚属共有5种8亚种。为探讨四照花亚属nrDNA ITS序列的致同进化不完全现象及假基因产生的可能原因,分析了该亚属4种(每种1~2个居群)共21个个体的nrDNA ITS序列。结果表明,这些类群的nrDNA ITS存在多态性,通过分析这些nrDNA ITS克隆序列的G+C含量、5.8S保守基序和二级结构最小自由能,推测其可能存在假基因。系统发育研究结果显示所有nrDNA ITS序列分成5个分支,同一个体的不同拷贝被分别置于两个甚至多个分支中,且不同分支显示了不同种间关系。四照花亚属物种个体内部存在nrDNA ITS不完全致同进化,可能归咎于不完全的世系分选(incomplete lineage sorting)、种间杂交或多倍化等进化事件,从而导致基因组内nrITS区序列出现多态性,同时也导致难以通过外部形态来划分亚属内种间界限。     

RAPD patterns,nrDNA ITS sequences and morphological patterns inSilene sectionSedoideae (Caryophyllaceae)

Hierarchical patterns inSilene sect.Sedoideae were investigated using random amplified polymorphic DNA (RAPD), nucleotide sequences of the internal transcribed spacer (ITS) regions of the 18S–28S nuclear ribosomal DNA, and discrete morphological characters. All data sets firmly supported the species recognized. The RAPD data offered the best resolution at the intraspecific level, supporting the current intraspecific classifications ofS. sedoides andS. integripetala. The ITS sequences and the morphological data gave poor resolution within species, and the three data sets disagreed about the relationships among species. The signal from the RAPD data was strongest and remained when the total data set was analysed. The three data sets all support an amphiploid origin ofS. aegaea, with the strongest evidence from the ITS sequences. Incongruences among data sets as well as merits and shortcomings of each are discussed. The robustness of the results can be evaluated using perturbations of data, i.e., bootstrap and jackknife of taxa and characters. These methods should not be taken as methods of statistical inference at the taxonomic level, because unbiased sampling appears impossible. RAPD data, however, come close to being suitable for statistical estimation of hierarchies at the genome level, but several methodological problems have to be solved.     

Molecular phylogenetic and morphological analyses of Oidium heveae, a powdery mildew of rubber tree

Powdery mildew of rubber tree caused by Oidium heveae is an important disease of rubber plantations worldwide. Identification and classification of this fungus is still uncertain because there is no authoritative report of its morphology and no record of its teleomorphic stage. In this study, we compared five specimens of the rubber powdery mildew fungus collected in Malaysia, Thailand, and Brazil based on morphological and molecular characteristics. Morphological results showed that the fungus on rubber tree belongs to Oidium subgen. Pseudoidium. Nucleotide sequence analysis of the ribosomal DNA internal transcribed spacer (ITS) region and the large subunit rRNA gene (28S rDNA) were conducted to determine the relationships of the rubber powdery mildew fungus and to link this anamorphic fungus with its allied teleomorph. The results showed that the rDNA sequences of the two specimens from Malaysia were identical to a specimen from Thailand, whereas they differed by three bases from the two Brazilian isolates: one nucleotide position in the ITS2 and two positions in the 28S sequences. The ITS sequences of the two Brazilian isolates were identical to sequences of Erysiphe sp. on Quercus phillyraeoides collected in Japan, although the 28S sequences differed at one base from sequences of this fungus. Phylogenetic trees of both rDNA regions constructed by the distance and parsimony methods showed that the rubber powdery mildew fungus grouped with Erysiphe sp. on Q. phillyraeoides with 100% bootstrap support. Comparisons of the anamorph of two isolates of Erysiphe sp. from Q. phillyraeoides with the rubber mildew did not reveal any obvious differences between the two powdery mildew taxa, which suggests that O. heveae may be an anamorph of Erysiphe sp. on Q. phillyraeoides. Cross-inoculation tests are required to substantiate this conclusion.     

Comparisons of phylogenetic hypotheses among different data sets in dwarf dandelions (Krigia,Asteraceae): Additional information from internal transcribed spacer sequences of nuclear ribosomal DNA

The internal transcribed spacer (ITS) region of the 18 S–25 S nuclear ribosomal DNA repeat was sequenced from 19 populations of the tribeLactuceae, including all species of dwarf dandelion (Krigia) and five outgroup genera. The incidence of length changes and base substitutions was at least two times higher for ITS 1 than ITS 2. Interspecific sequence divergence withinKrigia averaged 9.62% (1.61%–15.19%) and 4.26% (0%–6.64%) in ITS 1 and ITS 2, respectively. Intergeneric sequence divergence ranged from 15.6% to 44.5% in ITS 1 and from 8.0% to 28.6% in ITS 2. High sequence divergence and homoplasy among genera of tribeLactuceae suggest that the phylogenetic utility of ITS sequence data is limited to interspecific studies or comparisons among closely related genera. Trees generated from ITS sequences are essentially identical to those from restriction site comparisons of the entire nuclear ribosomal (nr) DNA region. The degree of tree resolution differed depending on how gaps were treated in phylogenetic analyses. The ITS trees were congruent with the chloroplast DNA and morphological phylogenies in three major ways: 1) the sister group relationship betweenKrigia andPyrrhopappus; 2) the recognition of two monophyletic sections,Krigia andCymbia, in genusKrigia; and 3) the monophyly of theK. occidentalis-K. cespitosa clade in sect.Cymbia. However, the two nrDNA-based trees are not congruent with morphology/chloroplast DNA-based trees for the interspecific relationships in sect.Krigia. An average of 22.5% incongruence was observed among fourKrigia data sets. The relatively high degree of incongruence among data sets is due primarily to conflict between trees based on nrDNA and morphological/cpDNA data. The incongruence is probably due to the concerted evolution of nrDNA repeating units. The results fromKrigia and theLactuceae suggest that nrDNA data may have limited utility in phylogenetic studies of plants, especially in groups which exhibit high levels of sequence divergence. Our combined phylogenetic analysis as a total evidence shows the least conflict to each of the individual data sets.     

Molecular features of a defined genetic marker for the determination of the Porphyra tenera lineage

Nucleotide sequences of the nuclear SSU rDNA and ITS1 are presented as a defined genetic marker for Porphyra tenera as a species. Exon nucleotide sequences were identical within all the P. tenera specimens. Intron nucleotide sequences varied between populations. The introns and ITS1 variations are presented as defined genetic markers to establish the Porphyra tenera strains. Wild-collected thalli identified by morphological systematics, from five populations of Porphyra tenera throughout Japan, were discriminated by comparing sequences of the various regions utilizing the results of this and previous studies.     

球孢白僵菌种内比较线粒体基因组学分析

【目的】明确球孢白僵菌种内线粒体基因组的分化程度。【方法】从GenBank下载已知的球孢白僵菌6个菌株线粒体基因组序列,详细分析基因组的组成结构,比较外显子区、内含子区和基因间区的碱基变异情况,分析菌株间的系统发育关系。【结果】球孢白僵菌不同菌株的线粒体基因组大小为28.8–32.3 kb,都有14个常见的核心蛋白编码基因、2个rRNA基因和25个tRNA基因,具有很强的共线性关系。但是,不同菌株含有的线粒体内含子数目存在差异(2–5个/菌株),在cox1、cox2和nad1基因中表现出内含子插入/缺失多态性,这是导致线粒体基因组大小变化的主要因素。对外显子、内含子和基因间区的碱基变异情况进行分析,发现内含子和基因间区相对变异较大,而外显子区相对变异较小。系统发育分析发现,这些球孢白僵菌菌株以很高的支持度聚在一起,具有相同内含子分布规律的菌株也具有较近的聚类关系。【结论】本研究首次报道球孢白僵菌因内含子数目不同、插入缺失突变和单核苷酸变异等在线粒体基因组上表现出较大程度的遗传分化,为认识真菌种内线粒体基因组分化提供了新的证据。     

Lengths and nucleotide sequences of the internal spacers of nuclear ribosomal DNA in gymnosperms and pteridophytes

The nucleotide sequences of the internal transcribed spacers (ITS1 and ITS2) of the nuclear ribosomal DNA were analyzed in species belonging to gymnosperms and pteridophytes. The lengths of the ITSs of sixteen species of gymnosperms and seven species of pteridophytes were estimated. The gymnosperms have ITS1 regions larger than those observed in the pteridophytes and angiosperms (ca. 610–3100 bp versus 159–360 bp). On the other hand, the ITS2 regions appear to be of a conserved length (182–370 bp). We have determined the complete nucleotide sequences of ITS regions from four gymnosperm species and five pteridophyte species by cloning the PCR products. Sequence analysis showed the presence of three short tandem arranged subrepeats of about 70 bp in the 1112 bp ITS1 ofEphedra fragilis. Pyrimidine rich (about 90%) DNA segments of 40–50 bp were observed in the ITS1 ofGinkgo biloba. A highly conserved 16 bp long sequence known to be present in the ITS1 of the angiosperm species has been also found in the ITS1 ofCycas revoluta, Taxus baccata andEphedra fragilis. Dedicated to Prof.Emilio Battaglia.     

Botryosphaeria spp. isolated from apple and several deciduous fruit trees are divided into three groups based on the production of warts on twigs, size of conidia, and nucleotide sequences of nuclear ribosomal DNA ITS regions

We examined the phytopathological and biological characters ofBotryosphaeria spp. isolated from apples and other deciduous fruit trees, and determined the nucleotide sequences of their rDNA ITS regions. TheBotryosphaeria isolates from deciduous fruit trees can be divided into three groups based on their production of warts on twigs, size of the conidia, and nucleotide sequences of rDNA ITS 1, ITS 2 and 5.8S rDNA. Isolates ofBotryosphaeria in ITS group A produced conidia of intermediate size and showed warts on infected twigs prior to the development of ring rot on fruit. This group was common on deciduous fruit trees in Japan as a causal agent of ring rot and wart bark diseases of apples and pears; and it appears similar to theB. dothidea from the US that was isolated from apple exhibiting white rot. The ITS group BBotryosphaeria produced small conidia and induced shoot blight without wart development prior to the development of ring rot on fruit. This group was localized on pear, persimmon, and kiwi fruit in restricted areas of Japan. The ITS group CBotryosphaeria consisted ofB. obtusa, the causal agent of apple black rot in the US, which produced large dark brown conidia.     

Ribosomal DNA-ITS sequence polymorphism in the sugarcane rust,Puccinia kuehnii

The two highly divergent ITS types previously observed in isolates ofPuccinia kuehnii were amplified from the same isolates through the use of ITS type-specific primers for PCR and are therefore considered as polymorphisms of ITS regions within the species. Although homology of sequences of one of the ITS types with otherPuccinia species was of expected levels, significantly high homology of sequences of the other type with those ofCronartium members indicates that abnormal genetic events led to the occurrence of these polymorphic regions. These results indicate that ITS gene tree phylogeny may not reflect true species phylogeny in this group of rust fungi. Rather, D1/D2 region tree phylogeny, which was concordant with the differences in morphology with and among related rusts, more correctly reflects phylogenetic relationships of sugarcane and related grass rusts. contribution No. 159, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba.     

Phylogenetic and evolutionary implications of nuclear ribosomal DNA variation in dwarf dandelions (Krigia,Lactuceae, Asteraceae)

Restriction site and length variations of nrDNA were examined for 51 populations of seven species ofKrigia. The nrDNA repeat ranged in size from 8.7 to 9.6 kilobase (kb). The transcribed region, including the two ITSs, was 5.35 kb long in all examinedKrigia populations. In contrast, the size of the nontranscribed IGS varied from 3.35 to 4.25 kb. Eight different types of length-variations were identified among the 51 populations, including distinct nrDNA lengths in the tetraploid and diploid populations of bothK. biflora andK. virginica. However, a few variations were detected among populations of the same species or within a cytotype. All populations ofKrigia sect.Cymbia share a 600 bp insertion in IGS near the 18 S gene, and this feature suggests monophyly of the section. AllKrigia spp. had a conjugated type of subrepeat composed of approximately 75 basepairs (bp) and 125 bp. Base modifications in the gene coding regions were highly conserved among species. Forty-five restriction sites from 15 enzymes were mapped, 24 of which were variable among populations. Only four of the variable sites occurred in the rRNA coding region while 20 variable sites were detected in the noncoding regions. Collectively, 25 enzymes generated about 66 restriction sites in each nrDNA; this amounts to about 4.3% of the nrDNA repeat. A total of 50 restriction sites was variable, 28 of which were phylogenetically informative. Phylogenetic analyses of site mutations indicated that two sections ofKrigia, sect.Cymbia and sect.Krigia, are monophyletic. In addition, relationships among several species were congruent with other sources of data, such as cpDNA restriction site variation and morphology. Both length and restriction site variation supported an allopolyploid origin of the hexaploidK. montana. The average sequence divergence value inKrigia nrDNA was 40 times greater than that of the chloroplast DNA. The rapid evolution of nrDNA sequences was primarily due to changes of the IGS sequences.     

<Emphasis Type="Italic">Umbelopsis gibberispora</Emphasis> sp. nov. from Japanese leaf litter and a clarification of <Emphasis Type="Italic">Micromucor ramannianus </Emphasis>var. <Emphasis Type="Italic">angulisporus</Emphasis>

 Umbelopsis gibberispora is described as a new species in the genus Umbelopsis, Umbelopsidaceae, Mucorales. The species differs from others in this genus by ellipsoidal sporangiospores with unilaterally thickened walls. Phylogenetic analyses based on nuclear large subunit ribosomal DNA (nLSU rDNA) partial sequences suggest that U. gibberispora, U. swartii, and U. westeae form a clade together with the strains of Umbelopsis ramanniana. The ex-type strain of Micromucor ramannianus var. angulisporus is found to be very close to Umbelopsis vinacea, whereas other isolates identified under the former name in the sense of Linnemann fall in the U. ramanniana subclade. For these isolates, a new species, Umbelopsis angularis, is introduced. Phylogenetic relationships among Umbelopsis species are discussed related to their attributes of the sporangial wall and mature spore shapes. Received: August 27, 2002 / Accepted: March 11, 2003 Acknowledgments We thank Dr. Takashi Ohsono, Graduate School of Agriculture, Kyoto University, Japan, for providing the strain of U. gibberispora (CBS 109328). We also thank Dr. Wieland Meyer, University of Sydney, Australia for access to the phylogenetic tree based on ITS sequence data before publishing, and Dr. Richard C. Summerbell, Centraalbureau von Schimmelcultures, the Netherlands, for linguistic corrections.     

Identification of Cyst Nematodes of Agronomic and Regulatory Concern with PCR-RFLP of ITS1

The first internally transcribed spacer region (ITS1) from cyst nematode species (Heteroderidae) was compared by nucleotide sequencing and PCR-RFLP. European, Asian, and North American isolates of five heterodefid species were examined to assess intraspecific variation. PCR-RFLP patterns of amplified ITS1 DNA from pea cyst nematode, Heterodera goettingiana, from Northern Ireland were identical with patterns from Washington State. Sequencing demonstrated that ITS1 heterogeneity existed within individuals and between isolates, but did not result in different restriction patterns. Three Indian and two U.S. isolates of the corn cyst nematode, Heterodera zeae, were compared. Sequencing detected variation among ITS1 clones from the same individual, between individuals, and between isolates. PCR-RFLP detected several restriction site differences between Indian and U.S. isolates. The basis for the restriction site differences between isolates from India and the U.S. appeared to be the result of additional, variant ITS1 regions amplified from the U.S. isolates, which were not found in the three India isolates. PCR-RFLP from individuals of the U.S. isolates created a composite pattern derived from several ITS1 types. A second primer set was specifically designed to permit discrimination between soybean (H. glycines) and sugar beet (H. schachtii) cyst nematodes. Fok I digestion of amplified product from soybean cyst nematode isolates displayed a uniform pattern, readily discernible from the pattern of sugar beet and clover cyst nematode (H. trifolii).     

Analysis of nucleotide sequence polymorphism of internal transcribed spacers of ribosomal genes in diploid <Emphasis Type="Italic">Aegilops</Emphasis> (L.) species

The nucleotide sequence of the fragment of the internal transcribed spacer (ITS) of rDNA comprising the full-length ITS1, the gene encoding 5.8S rRNA, and part of the ITS2 sequence was determined in 22 samples of five diploid Aegilops species. The full alignment length of compared sequences was 524 bp. Species-specific substitutions were found in the ITS nucleotide sequence of rDNA of different Aegilops species. Intraspecific differences in ITS structure in diploid Aegilops species were detected for the first time. Polymorphism of the ITS nucleotide sequence within the same sample was revealed, which might be due either to differences between the genomes of individual plants comprising the sample or to the presence of several types of ribosomal genes in the genome of one plant. In general, both interspecific and intraspecific variability of the ITS nucleotide sequences of rDNA is extremely low. In total, 26 variable sites, twelve of which were informative, were identified.__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 2, 2005, pp. 193–197.Original Russian Text Copyright © 2005 by Goryunova, Chikida, Gori, Kochieva.