Aegilops Accessions Research Articles

Response of Three Accessions of Jordanian Aegilops Crassa Boiss and Durum Wheat to Controlled Drought

Drought is a major abiotic stress that is threatening the production and the survival of many crops such as cereals. The response of three Aegilops crassa accessions (C1, C2 and C3) that inhabit areas with different rates of rainfall and durum wheat to controlled drought (with soil moisture of 50% field capacity) was tested in terms of changes in: relative water content, chlorophyll content, chlorophyll fluorescence and biomass accumulation. At the end of drought treatment, a slightly significant decrease in relative water content (RWC) was shown in two Ae. crassa accessions (C2 and C3). RWC of C1 accession and durum wheat showed no change. In all Aegilops accessions and durum wheat, the effect of drought on chlorophyll content and chlorophyll fluorescence was minimal. A differential response to drought in terms of biomass accumulation was revealed. Ae. crassa C2 and C3 accessions that are adapted to semiarid and arid areas, respectively, showed no significant difference in their biomass under drought stress. The biomass of C1 accession that is adapted to well-watered area was significantly decreased. A highly significant decrease in biomass was also shown in durum wheat. Hence, C2 and C3 accessions of Ae. crassa are promising genetic sources for the genetic engineering of drought tolerant wheat plants. Future understanding the molecular basis of how drought-tolerant Aegilops species respond to drought stress, can be one of the approaches to improve drought tolerance in wheat.

Genetic diversity and relationship analysis among accessions of Aegilops ssp. in Turkey using amplified fragment length polymorphism (AFLP) markers

Amplified fragment length polymorphism (AFLP) DNA markers were used to assess the genetic diversity and relationships between 55 accessions of genus Aegilops , including the species Aegilops triuncialis L. (UUCC), Aegilops geniculata Roth (MMUU), Aegilops cylindrica Host (CCDD) and Aegilops umbellulata Zhuk (UU). The samples were collected from Aegean region and East Anatolia, Turkey. 16 AFLP selective primer combinations generated a total of 3200 polymorphic amplification products. 50 Aegilops accessions were analyzed using the data analysis software, unweighted pair-group method arithmetic average (UPGMA) method and numerical taxonomy and multivariate analysis system (NTSYSpc-2.02k). The similarity index coefficients were calculated according to simple matching coefficient. Using 16 AFLP primer combinations, species from Aegean region and east Anatolia were clustered as four major groups. Aegilops species having U genome clustered together and A. cylindrica host was out grouped. Keywords: Aegilops cylindrica, Aegilops triuncialis, Aegilops umbellulata, Aegilops geniculata, amplified fragment length polymorphism (AFLP), Li-COR, genetic relationship, unweighted pair-group method arithmetic average (UPGMA), principle coordinate analysis.

Genetic diversity of Greek Aegilops species using different types of nuclear genome markers

Random Amplified Polymorphic DNA (RAPD) and Inter-Simple Sequence Repeat (ISSR) analyses were used to evaluate genetic variability and relationships of Greek Aegilops species. Thirty-eight accessions of seven Greek Aegilops species [ Ae. triuncialis (genome UC), Ae. neglecta (U M), Ae. biuncialis (U M), Ae. caudata (C), Ae. comosa (M), Ae. geniculata ( MU) and Ae. umbellulata (U)] as well as Triticum accessions were studied. Nineteen RAPD and ten ISSR primers yielded 344 and 170 polymorphic bands, respectively, that were used for the construction of dendrograms. Regardless of the similarity coefficient and marker type used, UPGMA placed 38 Aegilops accessions into one branch while the other branch consisted of wheat species. Within the Aegilops cluster, subgroups were identified that included species that shared the same genome or belonged to the same botanical section. Within the Triticum cluster, two robust subgroups were formed, one including diploid wheat and another including polyploid wheat. In conclusion, results showed that there is genetic diversity in the Greek Aegilops species studied, and clustering based on genetic similarities was in agreement with botanical classifications.

English

  In this study karyotype and chromosome characteristics of the nine accessions ofAegilops crassa species obtained from gene bank of Seed and Plant Improvement Research Institute (SPII) of Iran and one accession collected by authors were inspected. Aceto-iron-hematoxilin staining method was used to stain chromosomes. For each accession, chromosome characteristics including long and short arms, chromosome lengths, arm ratio index and relative chromosome lengths were measured using micro measure 3.3 software. Results revealed that all of the studied accessions were tetraploid (2n = 4x = 28) and consisted of 13 pairs of metacentric and one pair of submetacentric chromosomes, of which two pairs were satellite chromosomes. Karyotype formula for these accessions were 13 m + 1 sm. Arm ratio index value of chromosomes ranged from 1.11 in chromosome number 6 to 1.77 in chromosome number 12. The B chromosomes were not seen in any of the accessions. Karyological characteristics of theseaccessions were similar to each other. However, some differences were observed between the accessions in some chromosome characteristics.   Key words: Aegilops Crassa, karyotype, aceto-iron-hematoxilin staining, satellite chromosome.

Cloning and characterization of novel low molecular weight glutenin subunit genes from two Aegilops species with the C and D genomes

Four novel low molecular weight glutenin subunit genes (designated as AmLMWm1, AcLMWm1, AcLMWm2 and AcLMWm3) were isolated and characterized from the genomic DNA of two Aegilops accessions, AmLMWm1 from Aegilops markgrafii (Greuter) K.Hammer (2n = 2x = 14, CC), AcLMWm1, AcLMWm2 and AcLMWm3 from Aegilops cylindrica Host (2n = 4x = 14, CCDD). The coding regions of AmLMWm1, AcLMWm1, AcLMWm2 and AcLMWm3 were 1,092, 1,119, 912 and 936 bp in length, encoding 39,168, 40,297, 31,961 and 33,396 Da LMW-GS, respectively. In order to confirm their authenticity, these LMW-GS genes were successfully expressed in E.coli. The four novel genes belong to LMW-m types and, according to the first and seventh cysteine positions, were further classified as types III, I, IV and V, respectively. Among these novel genes, AmLMWm1 and AcLMWm1 possessed a longer repetitive domain (20 and 22 repeats) than common LMW-GS genes, which was considered to be associated with good dough quality of wheat. Phylogenetic analysis showed C and D genomes of Aegilops involved in this study had LMW-GS loci similar to those of the A, B, and D genomes in common wheat.

The application of wheat microsatellite markers for the detection of interspecific variation in tetraploidAegilopsspecies with C and U genomes

We report the application of wheat microsatellites (GWM) for the investigation of Aegilops species carrying C and U genomes. Overall, 89 microsatellite markers located in A, B and D genomes of bred wheat were used for the analysis of Ae. cylindrica Host. (CCDD) and Ae. triuncialis L. (UUCC). Ae. tauschii Coss. (DD) was included as a control of amplification of the D-genome markers. Twelve, eleven and seven of the A-genome-specific markers produced amplification fragments in Ae. cylindrica, Ae. triuncialis and Ae. tauschii, respectively. The level of amplification of the B-genome markers was similar in all investigated species and amounted to 60–65%. The markers of the D genome showed a significantly higher polymorphism level among Ae. tauschii accessions than among those of Ae. cylindrica. Twenty-one microsatellite markers revealing polymorphism in Ae. cylindrica and Ae. triuncialis can be used as a markers for discrimination of C and U genomes. The results of microsatellite analysis were used to estimate genetic relationships among the Aegilops species. The dendrogram distinguished all Aegilops accessions and clustered them into three groups according to their species classification. There was no strong relation between the molecular data of the studied accessions and their geographical region of origin. Obtained data could be utilized for characterization and assessing genetic diversity of wild wheat relatives with C and U genomes.

Genomic diversity of germinating scutellum specific gene P23k in barley and wheat

P23k is a 23 kDa protein involved in sugar translocation in the scutellum of germinating barley seeds. The present study was carried out to provide the genomic characterization for P23k gene in terms of copy number, chromosome mapping, genetic mapping and expression analysis in germinating sculletum in two major Triticeae crops, barley and wheat, and their relatives. Southern blotting showed that a variable copy number with different restriction fragment sizes was found among 15 Hordeum accessions, while low copy number were found to be conserved in 23 Triticum and 3 Aegilops accessions. Genetic and physical mapping study identified that the P23k gene is duplicated in wild and cultivated barley on chromosomes 1H, 2H, and 3H, and further tandem duplication on chromosomes 1H and 3H. In contrast, the wheat P23k is located on chromosome 3A of durum wheat and at the distal portion of the long arms of 3A and 3D chromosomes of bread wheat. Northern blotting showed remarkably high accumulation of P23k transcript in the germinating scutellum in cultivated and wild barley, whereas very few or no accumulation was detected in diploid, tetraploid, and hexaploid wheat accessions. The present study suggests a simple scenario where the ancestral P23k is encoded on the distal portion of an ancestral chromosome of homoeologous chromosome 3. Beside of polyploidy, dispersed and tandem duplications could trigger generation of the P23k family in the Hordeum lineage, while an ancestral P23k has been conserved in homoeologous 3A and 3D chromosomes in the wheat lineage.

Development and characterization of Triticum aestivum– Aegilops kotschyi amphiploids with high grain iron and zinc contents

Synthetic amphiploids betweenTriticum aestivum(AABBDD) landrace Chinese Spring (PhI) and cultivar WL711 with different accessions ofAegilops kotschyi(UUSlSl) were developed through colchicine treatment of sterile hybrids. TheF1hybrids and amphiploid plants were intermediate between the parents for plant morphology and spike characteristics. Meiotic metaphase chromosome analysis of theF1hybrids (ABDUSl) showed the expected chromosome number (35) and very little but variable homoeologous chromosome pairing. The amphiploids (AABBDDUUSlSl), however, had variable frequency of univalents at meiotic metaphase-I. The SDS–PAGE of high molecular weight glutenin subunits of amphiploids along with the parents showed the presence and expression of all the parental genomes in the amphiploids. The amphiploids with seeds as large as that of wheat cultivars had higher grain, flag leaf and grain ash iron and zinc concentrations than the wheat parents and comparable with those of theirAe. kotschyiparents suggest thatAe. kotschyipossesses a distinctive genetic system for the micronutrient uptake, translocation and sequestration than the wheat cultivars. This could, however, be demonstrated unequivocally only with comprehensive data on biomass, grain yield and harvest index of theAegilopsdonors and the synthetic amphiploids, which is not feasible due to their shattering and hard threshing. The use of amphiploids for the transfer of high iron and zinc concentrations and development of alien addition and substitution lines in wheat is in progress.

Chemotaxonomic Studies on Aegilops L. (Poaceae) In Iran

This study, using seed storage protein electrophoresis, evaluates the taxonomic status of the Aegilops L. species and the variation between the species. Therefore, with the seeds of seven species and 46 accessions of Aegilops, the prolamin was separated. On the base of the banding patterns, the cluster analysis among these species was studied. The results of this study show that most of the tetraploid species (2n = 4x = 28; x = 7) and the diploid species (2n = 2x = 14; x = 7) were grouped with each other. This document illustrates that a high gene flow exists among the diploid species. Further, high variability was observed among the accessions of Aegilops species. Morphologically; some of the species, which are very similar (Ae. umbellulata Zhuk., Ae. columnaris Zhuk.), have exactly been distinguished in this method. Chemo taxonomically, the status of these species was partially illustrated. Finally, Prolamin is an appropriate marker for identifying the taxonomic position of Aegilops species.

Sources of resistance to Hessian fly (Diptera: Cecidomyiidae) in Syria identified among Aegilops species and synthetic derived bread wheat lines

The Hessian fly, Mayetiola destructor (Say), is a major pest of wheat in North Africa, southern Europe, North America, and northern Kazakhstan. It is believed this pest (like wheat) originated in West Asia. The Syrian Hessian fly biotype has been found to be the most virulent worldwide, and has been used at the International Center for Agricultural Research in the Dry Areas (ICARDA) for screening wheat and its wild relatives to identify new sources of resistance. The screening was conducted in an insect rearing room set at 20°C and 70% RH using a Hessian fly population collected from Lattakia region, Syria. The experimental design was a randomized complete block with four replications. ‘Nasma’ (bread wheat) and ‘Cando’ (durum wheat) were used as susceptible and resistant checks, respectively. A total of 623 lines/accessions of wheat and its wild relatives (Aegilops and Triticum) were evaluated. Twenty-nine Aegilops accessions and four synthetic derived bread wheat lines were found resistant. The presence of dead first instars confirmed the resistance reaction and also showed that antibiosis is the major mechanism of resistance in these materials. These sources of resistance are used in ICARDA’s wheat breeding programs for the development of Hessian fly-resistant germplasm/varieties.

Assessment of genetic diversity in Triticum spp. and Aegilops spp. using AFLP markers

Genetic diversity among some wild relatives of wheat was estimated using amplified fragment length polymorphism (AFLP) and morphological markers. Thirty one Triticum and Aegilops genotypes including twenty-four Triticum and Aegilops accessions belonging to five diploid (Triticum baeoticum, Triticum monococcum, Aegilops umbellulata, Aegilops caudata and Aegilops tauschii), five tetraploid (Triticum dicoccoides, Triticum dicoccum, Aegilops crassa (4x), Aegilops cylindrica, Aegilops triuncialis) and two hexaploid (Triticum compactum, A. crassa (6x)) species sampled from different ecogeographical regions of Iran; a durum wheat cultivar 'Langdon', a local wheat cultivar 'Roshan', a wheat cultivar 'Chinese spring' and four synthetic hexaploid wheats were evaluated. Genetic diversity among wheat accessions was estimated using 14 PstI:MseI primer pair combinations. Of the approximately 414 detected AFLP markers, 387 (93.5%) were polymorphic with 28 bands per used primer pair. Cluster analysis of 31 accessions belonging to the 15 species by UPGMA cluster analysis based on Jaccard’s similarity estimates for AFLP data divided all accessions into two major clusters reflecting almost their genome composition. The first one included wheat species having A and AB genomes, while second cluster included wheat species having C, D, AB, CD, UC, DM, DDM and ABD genomes. The genetic similarity coefficients ranged from 0.12 between Ae. glabra and accession number 3 of T. monococcum and 0.57 between A. crassa (6x) and Ae. crassa (4x-6x). Two Aegilops species of A. umbellulata and A. caudata were ranked as the second most related species.

Sequence diversity and copy number variation of Mutator-like transposases in wheat

Partial transposase-coding sequences of Mutator-like elements (MULEs) were isolated from a wild einkorn wheat, Triticum urartu, by degenerate PCR. The isolated sequences were classified into a MuDR or Class I clade and divided into two distinct subclasses (subclass I and subclass II). The average pair-wise identity between members of both subclasses was 58.8% at the nucleotide sequence level. Sequence diversity of subclass I was larger than that of subclass II. DNA gel blot analysis showed that subclass I was present as low copy number elements in the genomes of all Triticum and Aegilops accessions surveyed, while subclass II was present as high copy number elements. These two subclasses seemed uncapable of recognizing each other for transposition. The number of copies of subclass II elements was much higher in Aegilops with the S, Sl and D genomes and polyploid Triticum species than in diploid Triticum with the A genome, indicating that active transposition occurred in S, Sl and D genomes before polyploidization. DNA gel blot analysis of six species selected from three subfamilies of Poaceae demonstrated that only the tribe Triticeae possessed both subclasses. These results suggest that the differentiation of these two subclasses occurred before or immediately after the establishment of the tribe Triticeae.

Classification of wheat low-molecular-weight glutenin subunit genes and its chromosome assignment by developing LMW-GS group-specific primers

On the basis of sequence analysis, 69 known low-molecular-weight glutenin subunit (LMW-GS) genes were experimentally classified into nine groups by the deduced amino acid sequence of the highly conserved N-terminal domain. To clarify the chromosomal locations of these groups, 11 specific primer sets were designed to carry out polymerase chain reactions (PCR) with the genomic DNA of group 1 ditelosomic lines of Chinese Spring, among which nine primer sets proved to be LMW-GS group-specific. Each group of LMW-GS genes was specifically assigned on a single chromosome arm and hence to a specific locus. Therefore, these results provided the possibility to predict the chromosome location of a new LMW-GS gene based on its deduced N-terminal sequence. The validity of the classification was confirmed by the amplifications in 27 diploid wheat and Aegilops accessions. The length polymorphisms of LMW-GS genes of groups 1 and 2, and groups 3 and 4.1 were detected in diploid A-genome and S-genome accessions, respectively. The diploid wheat and Aegilops species could be used as valuable resources of novel allele variations of LMW-GS gene in the improvement of wheat quality. The nine LMW-GS group-specific primer sets could be utilized to select specific allele variations of LMW-GS genes in the marker-assisted breeding.

Resistance to Leaf Rust, Stripe Rust, and Stem Rust in Aegilops spp. in Israel.

In all, 1,323 single plant accessions of Aegilops bicornis, A. kotschyi, A. longissima, A. ovata, A. searsii, A. sharonensis, A. speltoides, and A. variabilis collected from 18 regions in Israel and 2 adjacent regions in Lebanon and Egypt were evaluated for leaf rust (Puccinia triticina) and stripe rust (P. striiformis) resistance in field plots and for seedling resistance to leaf rust and stem rust (P. graminis f. sp. tritici) in greenhouse tests. Nearly all accessions of A. speltoides were highly resistant to leaf rust, stripe rust, and stem rust. A. longissima and A. ovata were highly resistant to stripe rust, whereas A. bicornis and A. kotschyi were highly susceptible. A. searsii was highly susceptible to stem rust, but 24 to 51% of accessions of A. bicornis, A. longissima, A. ovata, and A. variabilis were resistant to stem rust. Except for A. ovata and A. speltoides, more than 95% of the Aegilops accessions were susceptible to leaf rust caused by P. recondita alternating on Anchusa spp. Only Aegilops ovata was susceptible to P. recondita from Echium spp. A. bicornis, A. koschyi, and A. searsii were highly susceptible as seedlings to common wheat leaf rust caused by P. triticina. Most accessions of A. variabilis and about half of the accessions of A. longissima had good seedling resistance to P. triticina. Few accessions of A. ovata showed seedling resistance to the P. triticina population in Israel, but 30% were resistant to U.S. isolates. In field tests, A. bicornis showed high susceptibility to common wheat leaf rust, but more than 90% of the accessions of the other Aegilops spp. developed little or no leaf rust on adult plants. The Aegilops spp. in Israel and adjoining countries provide a rich and varied source of rust resistance for wheat breeding.

Ecological distribution and species diversity of Aegilops L. genus in Bulgaria

The genus Aegilops has an important potential utilization in wheat improvement because of its resistance to different biotic and abiotic stresses and close relation with the cultivated wheat. Therefore, a better knowledge of the eco-geographical distribution of Aegilops species and their collection and conservation are required. A total of 297 Aegilops accessions representing nine (five tetraploid and four diploid) species were collected in different regions of Bulgaria, and the ecological characteristics of the 154 explored sites were recorded. The distribution of the diploid species (Ae. caudata L., Ae. speltoides Tausch, Ae. umbellulata Zhuk. and Ae. comosa Sibth. and Sm.) was limited to specific environments in south-central Bulgaria. Tetraploid species were present in harsher environments than diploid species and showed wider adaptation and distribution. Species–environment relationships were analysed by considering the worldwide distribution of the species and their physiological resistance to abiotic stress. Aegilops cylindrica Host was more frequently found in northern Bulgaria and at high altitudes. Its distribution was closely related to its tolerance to low temperatures. Aegilops geniculata Roth and Ae. neglecta Req. ex Bertol. were absent in the north of Bulgaria, but widely distributed in low rainfall areas. Aegilops neglecta, more frost resistant than Ae. geniculata, was present at higher altitude. Aegilops biuncialis Vis. and Ae. triuncialis L. showed adaptation to a wide range of climatic conditions. The study of Aegilops species ecology and distribution in Bulgaria provided useful information for the future collection and for the genetic resource management in this region.

Evaluation of Aegilops tauschii Coss. for resistance to wheat stem rust and inheritance of resistance genes in hexaploid wheat

With the objective to identify new sources of resistance to wheat stem rust, a collection of 169 accessions ofAegilops tauschii, obtained from the IPK genebank at Gatersleben, Germany, were screened for resistance undercontrolled conditions. Fourteen (8%) accessions were resistant to stem rust among which 10 were highly resistant(IT 5 ; and 1) and four exhibited a moderately resistance reaction (IT 5 2). From the synthetic hexaploids whichwere produced by hybridizing resistant Ae. tauschii with susceptible Triticum durum, six synthetics expressed ahigh level of stem rust resistance similar to their corresponding diploid parents, while five displayed either areduced or complete susceptibility compared to their Ae. tauschii parents. This suppression of resistance at thehexaploid level suggests the presence of suppressor genes in the A and/ or B genomes of the T. durum parents.Inheritance of resistance from crosses of five stem rust resistant synthetic hexaploids with two susceptible T.aestivum genotypes revealed that three of the synthetics (syn 101, syn 601 and syn 801) possessed one dominantgene each, syn 111 has two different dominant genes and syn 116 has two complementary interacting genes forstem rust resistance. Intercrosses among the four stem rust resistant synthetic hexaploids indicated that the putativegenes conferring stem rust resistance in each of the synthetics are neither allelic nor closely linked to each other.

Identification of Aegilops germplasm with multiple aphid resistance

The greenbug, Schizaphis graminum(Rondani), the Russian wheat aphid, Diuraphis noxia (Mordvilko), and the bird cherry oat aphid, Rhopalosiphum padi(L.), annually cause several million dollars worth of wheat production losses in Europe and the United States. In this study, Triticum and Aegilops accessions from the Czech Research Institute of Crop Production and the Kansas State University Wheat Genetic Resources Center were evaluated for resistance to these aphids. Accessions with aphid cross-resistance were examined for expression of the antibiosis, antixenosis, and tolerance categories of resistance. Aegilops neglecta accession 8052 exhibited antibiotic effects toward all three aphids in the form of reduced intrinsic rate of increase (rm). The rm of greenbug (biotype I) on Ae. neglecta 8052 was significantly lower than that of greenbugs on plants of the susceptible U. S. variety Thunder bird. The rm of Russian wheat aphids was significantly lower on foliage of both Ae. neglecta 8052 and T. araraticum accession 168 compared to Thunderbird. The rm values of bird cherry oat aphids fed both Ae. neglecta 8052 and T. araraticum 168 were also significantly lower than those fed the susceptible accession T. dicoccoides 62. Neither Ae. neglecta 8052 or T. araraticum 168 exhibited tolerance to either greenbug biotype I or Russian wheat aphid. Preliminary data suggest that T. araraticum 168 may also possess tolerance to bird cherry oat aphid. New genes from Ae. neglecta 8052 and T. araraticum 168 expressing aphid antibiosis can be used to develop multiple aphid resistant wheat in the U. S. and Central Europe.

Physiological and morphological responses to water stress in Aegilops biuncialis and Triticum aestivum genotypes with differing tolerance to drought.

The physiological and morphological responses to water stress induced by polyethylene glycol (PEG) or by withholding water were investigated in Aegilops biuncialis Vis. genotypes differing in the annual rainfall of their habitat (1050, 550 and 225 mm year-1) and in Triticum aestivum L. wheat genotypes differing in drought tolerance. A decrease in the osmotic pressure of the nutrient solution from -0.027 to -1.8 MPa resulted in significant water loss, a low degree of stomatal closure and a decrease in the intercellular CO2 concentration (Ci) in Aegilops genotypes originating from dry habitats, while in wheat genotypes high osmotic stress increased stomatal closure, resulting in a low level of water loss and high Ci. Nevertheless, under saturating light at normal atmospheric CO2 levels, the rate of CO2 assimilation was higher for the Aegilops accessions, under high osmotic stress, than for the wheat genotypes. Moreover, in the wheat genotypes CO2 assimilation exhibited less or no O2 sensitivity. These physiological responses were manifested in changes in the growth rate and biomass production, since Aegilops (Ae550, Ae225) genotypes retained a higher growth rate (especially in the roots), biomass production and yield formation after drought stress than wheat. These results indicate that Aegilops genotypes, originating from a dry habitat have better drought tolerance than wheat, making them good candidates for improving the drought tolerance of wheat through intergeneric crossing.

Variation of specific morphological traits and ploidy level of five Aegilops L. species in Morocco.

ABSTRACT. Variation of specific morphological traits and ploidy level of five Aegilops L. species in Morocco.The genus Aegilops L. represents an important natural source of useful genes for wheat breeding, with particular emphasis on biotic and abiotic stress resistance. For successful crosses, the primarily step is to select appropriate Aegilops accessions. In this paper, we studied five Moroccan species of an Aegilops collection on the basis of spike structure and chromosome number. Twenty-eight specific morphological characters were used to differentiate the species. Statistical analyses, in particular the DFA, allowed the characterization of the genetic variability of the species; the two first standardized axes explained 96,2% of the total variability and 100% of the entities were classified within their own group. In addition, the dendrogram constructed using morphological data reveals a significant variability within and between species. Cytogenetic study revealed four species, A. geniculata Roth, A. triuncialis L., A. ventricosa Tausch and A.peregrina Maire & Weiller, to be tetraploid. However, A. neglecta Req. ex. Bertol., where only two accessions are represented in the collection, revealed to be hexaploid, and can then be classified as A. neglecta subsp. recta Chennav.Key words. Aegilops, Variation, Morphology, Ploidy, Morocco.RÉSUMÉ. Variation des caracteres morphologiques specificities et niveau de plordie de an(' espéces Aegilops L. au Maroc. Le genre Aegilops L. représente une importante source de genes, potentiellement utilisables dans Pamelioration des blés cultivés (Triticum spp.) notamment pour la resistance aux stress biotiques et abiotiques. Le choix des accessions Aegilops á employer, dans un programme d' hybridation interspécifique, necessite une caractérisation taxonomique et une evaluation préalables. L'objectif de ce travail a ete d'étudier des accessions, appartenant á 5 especes marocaines constituant une collection d'Aegilops, sur la base de caracteres morphologiques specifiques de l'épi et du niveau de ploYdie. La caractérisation phénotypique a été basée sur l'étude de 28 caracteres morphologiques qui discriminent entre les especes. Les resultats des analyses statistiques, en particulier de l'AFD, ont permis de caractériser la variabilite génetique de ces especes et ant donne un pourcentage d'appartenance á l'espece de 100%. Aussi, les deux premiers axes standardises expliquent 96,2% de la variabilité totale. Un demlrogramme a éte aussi construit, revelant une variabilite interspecifique. L'étude cytogenétique a révélé une tetraploYdie pour A. geniculata Roth, A. triuncialis L., A. ventricosa Tausch et A. peregrina Maire & Weiller. Quant á A. neglecta Req. ex. Bertol., une hexaploYdie a été mise en evidence pour les deux uniques accessions disponibles dans la collection, permettant de leur attribuer le nom A. neglecta subsp. recta Chennav.Mots clés. Aegilops, Variation, Morphologic, Plolidie, Maroc.

Morphological diversity and potential interest for wheat improvement of three Aegilops L., species from Bulgaria

A collection of fifty-two Aegilops accessions belonging to three tetraploid, self-pollinated species (Ae. cylindrica Host, Ae. geniculata Roth and Ae. neglecta Req. ex Bertol.) and sampled from different eco-geographical regions of Bulgaria was evaluated during three successive years on the basis of morphological descriptors and agronomical characters. Morphological diversity was analysed using a set of thirteen quantitative traits. Significant differences between populations were noted for most morphological traits, highest variation being observed in the three species for thousand kernel weight, grain weight per spike, plant height and earliness. There was not strong relation between the morphology of the studied accessions and their eco-geographical region of origin what was obviously due to marked differences between populations from the same region. The most important characters contributing to the eco-geographical differentiation were those related to vegetative growth in Ae. cylindrica and to grain production and earliness in Ae. geniculata. Considerable variability was found among and within species in response to biotic and abiotic stresses. Ae. cylindrica accessions exibited high frost resistance, but were the most susceptible to rusts and powdery mildew. At the opposite Ae. neglecta and Ae. geniculata were characterized with high level of foliar diseases resistance. Moreover, Ae. geniculataaccessions appeared to be the best adapted to drought conditions. Promising accessions were identified and are presently used to introgress potentially useful traits into wheat.