TRITICUM URARTU AND GENOME EVOLUTION IN THE TETRAPLOID WHEATS

The A genome of the tetraploid wheats (AABB, 2n = 28) shows 5-6 bivalents in crosses with Triticum boeoticum (2n = 14) and various Aegilops diploids (2n = 14). The B genome has never been similarly identified with any species, and is commonly thought to have been modified at the tetraploid level. Triticum boeoticum was presumably accepted as the A-genome donor because of its morphological similarity to the wild tetraploids and because it was formerly the only known wild diploid wheat. The B donor has been thought to be Ae. speltoides or another species of the Sitopsis section of Aegilops, but these diploids show pairing affinity with A rather than B. More recently, another diploid wheat, T. urartu, was found to be sympatric with T. boeoticum throughout the natural range of the tetraploids. The synthetic boeoticum-urartu amphiploid was virtually identical morphologically with the wild tetraploid wheats, whereas various boeoticum-Sitopsis amphiploids were markedly different. But the urartu genome, like those of T. boeoticum and Sitopsis, paired with A and not with B. However, cytological evidence also shows (1) that the genomes of any plausible parental combination pair with one another, (2) that the A and B genomes of the tetraploid wheats pair with one another in the absence of the gene Ph, and (3) that homoeologous chromosomes of the tetraploids have differentiated further, presumably as a result of diploidization. Consequently, chromosome pairing at Meiosis I can be expected to give ambiguous evidence regarding the identity of the tetraploid genomes with their parental prototypes. A hypothesis regarding the expected pairing affinities between tetraploid homoeologues that have differentiated from closely related parental chromosomes is advanced to explain the anomalous pairing behavior of the A and B genomes. Triticum boeoticum and T. urartu are inferred to be the parents of the tetraploid wheats.     

Basis of difference between reciprocal crosses involving Triticum boeoticum and T. urartu

Summary The boeoticum () X urartu () F₁ hybrids gave small, plump and viable seeds while the reciprocal crosses with T. urartu as the female parent had long, shrivelled and non-viable seeds. Reciprocal nuclear-substitution lines comprising the nucleus of one species into the cytoplasm of the other were developed through repeated backcrossing and were crossed as female parents with respective non-recurrent parents (the cytoplasm donors). The difference between the reciprocal crosses was presumably attributable to different boeoticum urartu genomic ratios in the triploid endosperm rather than to the cytoplasmic difference between the diploid wheats. The endosperm with two doses of the boeoticum and one of the urartu genome resulted in small, plump and viable seed while the endosperm of the reciprocal crosses with two doses of the urartu and one of the boeoticum genome led to large but shrivelled and non-viable seeds irrespective of the cytoplasmic type. One dose of the paternal genome in the triploid endosperm is probably not expressed in the presence of two doses of the maternal genome thereby leading to the difference between the reciprocal crosses. The results reported here indicate that difference between reciprocal crosses may not always be attributed to cytoplasmic difference between the parental species.     

THE RELATIONSHIPS BETWEEN MALE AND FEMALE FERTILITY AND AMONG TAXA IN DIPLOID WHEATS

Pollen stainability appears to be a reliable indication of the ultimate seed set in diploid interspecific hybrid and backcross populations in Triticum L. The correlation between percent pollen stained and number of seeds set is positive and highly significant (r = 0.92). Estimates of male and female fertility in the hybrids and backcrosses are interpreted to indicate that the domesticated diploid Triticum monococcum L. and wild diploid T. boeoticum Boiss. em. Schiem, are one and the same species, and that T. urartu Tum. is not a variety of monococcum or boeoticum, but rather a separate species. The F₁ hybrids and backcrosses between monococcum and boeoticum are normally male and female fertile. The F₁ hybrids between monococcum and urartu are completely sterile and complete to partial sterility exists in backcrosses.     

Genetic control of seed proteins in wheat

Summary Electrophoretic profiles of crude protein extracts from seed of F₁ hybrids and reciprocal crosses among diploid, tetraploid and hexaploid wheats were compared with those of their respective parental species. The electrophoretic patterns within each of three pairs of reciprocal crosses, T.boeoticum X T.urartu, T.monococcun X T. urartu and T.dicoccum X T. araraticum, were different from one another but were identical with those of their respective maternal parents. Protein bands characteristic of the paternal parents were missing in F₁ hybrid seed suggesting that the major seed proteins in wheat were presumably regulated by genotype of the maternal parent rather than by the seed genotype. However, in another three pairs of reciprocal crosses, T.boeoticum X T. durum, T.dicoccum X T.aestivum and T. zhukovskyi x T. aestivum, protein bands attributable to the paternal parents were present in the F₁ hybrid seeds indicating that the seed proteins were not always exclusively regulated by the maternal genotype. The expression of paternal genomes is presumably determined by dosage and genetic affinity of the maternal and paternal genomes in the hybrid endosperm. The maternal regulation of seed protein content is probably accomplished through the maternal control over seed size. The seed protein quality may, however, depend upon the extent of expression of the paternal genome.     

High molecular weight glutenin subunit variation in wild and cultivated einkorn wheats (Triticum spp.,Poaceae)

Variation in high molecular weight (HMW) glutenin subunit composition among wild and cultivated einkorn wheats (2n = 2x = 14, AA) was investigated using one- (SDS-PAGE and urea/SDS-PAGE) and two-dimensional (IEF × SDS-PAGE) electrophoretic analyses. The material comprised 150 accessions ofTriticum urartu, 160 accessions ofT. boeoticum, 24 accessions ofT. boeoticum subsp.thaoudar and 74 accessions of primitive domesticatedT. monococcum from many different germplasm collections. The biochemical characteristics of HMW-glutenin subunits ofT. boeoticum andT. monococcum were highly similar to one another but distinctly different from those ofT. urartu. All the species analysed were characterised by large intraspecific variation and only three HMW-glutenin subunit patterns were identical betweenT. boeoticum andT. monococcum. Consistent with the distinct nature ofT. urartu, all its HMW-glutenin patterns were different from those found inT. boeoticum andT. monococcum. The differences detected between these species might reflect their reproductive isolation and are consistent with recent nomenclatural and biosystematic treatments that recogniseT. urartu as separate species fromT. boeoticum andT. monococcum. The presence of three distinct glutenin components in some accessions of the species studied seems to be evidence for the existence of at least three active genes controlling the synthesis of the HMW-glutenin subunits in the A genome of wild and primitive domesticated diploid wheats. Results indicate also that HMW-glutenin subunits could represent useful markers for the evaluation of genetic variability present in different wild diploid wheat collections and subsequently for their conservation and future utilisation.     

Molecular characterization of vernalization loci VRN1 in wild and cultivated wheats

Background  

Variability of the VRN1 promoter region of the unique collection of spring polyploid and wild diploid wheat species together with diploid goatgrasses (donor of B and D genomes of polyploid wheats) were investigated. Accessions of wild diploid (T. boeoticum, T. urartu) and tetraploid (T. araraticum, T. timopheevii) species were studied for the first time.     

ANTHER MORPHOLOGY AND THE ORIGIN OF THE TETRAPLOID WHEATS

Anther morphology of various species of the genus Triticum is consistent with previous evidence that different biotypes of T. boeoticum (AA) and T. urartu (BB) contributed the respective A and B genomes to the emmer (A^eA^eB^eB^e) and timopheevi (A^tA^tB^tB^t) tetraploid complexes. Anther length of T. dicoccoides (2.8 mm) and T. araraticum (3.0 mm) is mid-way between that of T. boeoticum (3.6) and T. urartu (2.2) and the same as that of the sterile hybrid T. boeoticum X T. urartu. With respect to mode of dehiscence, post anthesis reflexion of anther lobes and twisting of the anthers, T. dicoccoides resembles T. boeoticum, whereas T. araraticum resembles T. urartu. With respect to anther apex, T. dicoccoides resembles neither T. boeoticum nor T. urartu but is identical with their F₁ hybrid. Among amphiploids involving four different Aegilops species and T. boeoticum lines, none could similarly account for the length or other diagnostic attributes of the tetraploid anthers. Anther morphology is consistent with the presumed genomic composition of the cultivated tetraploid and hexaploid wheats and seems to distinguish effectively the different genomic groups of the genus Triticum.     

Gliadin polymorphism in wild and cultivated einkorn wheats

To study the relationships between different species of the Einkorn group, 408 accessions of Triticum monococcum, T. boeoticum, T. boeoticum ssp. thauodar and T. urartu were analyzed electrophoretically for their protein composition at the Gli-1 and Gli-2 loci. In all the species the range of allelic variation at the loci examined is remarkable. The gliadin patterns of T. monococcum and T. boeoticum were very similar to one another but differed substantially from those of T. urartu. Several accessions of T. boeoticum and T. monococcum were shown to share the same alleles at the Gli-1 and Gli-2 loci, confirming the recent nomenclature that considers these wheats as different subspecies of the same species, T. monococcum. The gliadin composition of T. urartu resembled that of the A genome of polyploid wheats more than did T. boeoticum or T. monococcum, supporting the hypothesis that T. urartu, rather than T. boeoticum, is the donor of the A genome in cultivated wheats. Because of their high degree of polymorphism the gliadin markers may help in selecting breeding parents from diploid wheat germ plasm collections and can be used both to search for valuable genes linked to the gliadin-coding loci and to monitor the transfer of alien genes into cultivated polyploid wheats. Received: 8 July 1996 / Accepted: 12 July 1996     

Length variation of i-type low-molecular-weight glutenin subunit genes in diploid wheats

Allelic variation of the low-molecular-weight glutenin subunit (LMW-GS) is associated with the significant differences of dough quality in bread and durum wheat, and has been widely evaluated at protein level in wheat and its relatives. In this study, a PCR primer set, targeting the high variable repetitive domains, was employed to assay the length variation of i-type LMW-GS genes in the A-genomes of diploid wheats, the diploid progenitors of tetraploid and hexaploid wheat. A total of 71 accessions of diploid wheats, belonging to two wild and one cultivated species, were investigated. The higher variations of repetitive length in i-type LMW-GS genes were found in diploid wheats with Nei’s genetic variation index (H) of 0.834. The two wild species, T. boeoticum and T. urartu, were found to possess the similar degree of variability, with the Nei’s genetic variation index of 0.806 and 0.783, respectively. Less variation was detected in T. monococcum (H = 0.680), a cultivated species domesticated from T. boeoticum. The sufficient variation found in this study could be used as valuable source for the enrichment of genetic variations and the alteration of flour-processing properties of the cultivated wheat. To our knowledge, it was the first time that an analysis of length variation targeting a particular group of genes of LMW-GS complex multigene families was conducted. This article was submitted by the authors in English.     

Paternal regulation of seed development in wheat hybrids

Summary Diallel crosses among Triticum boeoticum (4 lines from different geographical areas), T.urartu, Aegilops squarrosa and Ae. speltoides exhibited reciprocal differences in hybrid seed morphology, endosperm development, and embryo viability. T. urartu and Ae. squarrosa as females with T. boeotiaum and Ae. speltoides lead to shrivelled inviable seed. T.boeoticum accessions as female with Ae.speltoides also lead to shrivelled seeds. The reciprocal crosses produced plump seeds which either resembled the maternal parent or showed size differences. By altering the endospermic genome ratios, hybrid seeds with 1 (PF)/1 (PM) showed extreme shrivelling whereas those with 4 (PF)/1 (PM) were medium shrivelled to plump. Genetic experiments involving hybrids of T. boeoticum, T. urartu and T. monococcum showed that a factor is present in pollen or male gametes, which shows dosage effect and which, by interacting with the maternal genome, leads to endosperm abortion.     

Genetic diversity in wild diploid wheats Triticum monococcum var. boeoticum and T. urartu (Poaceae)

Summary The genetic diversity of two wild diploid wheat species, Triticum monococcum var. boeoticum and T. urartu, was assessed using starch gel electrophoresis. Genetic diversity is uniformly low in both species. Number of alleles per locus was very low with a mean of 1.22 for T. monococcum var. boeoticum and 1.19 in T. urartu. Percentage of polymorphic loci was also low, with a mean of 19.71 for T. monococcum var. boeoticum and a mean of 18.35 for T. urartu. Mean gene diversity was low with a mean of 0.052 in populations of T. monococcum var. boeoticum and a mean of 0.040 in populations of T. urartu. Genetic affinities of the species and of populations were computed using Nei's identity index (NI). Overall genetic affinities of the two species are NI=0.697. The genetic affinities of different populations of a species are uniformly high with NIs ranging from 0.894 to 1.000 in T. monococcum var. boeoticum and from 0.898 to 1.000 in T. urartu.Research supported by the California Agricultural Experiment Station and the International Board of Plant Genetic Resources     

Morphological and molecular characterisation confirm that Triticum monococcum s.s. is resistant to wheat leaf rust

The three diploid wheat species Triticum monococcum, Triticum boeoticum and Triticum urartu differ in their reaction to wheat leaf rust, Puccinia triticina. In general, T. monococcum is resistant while T. boeoticum and T. urartu are susceptible. However, upon screening a large collection of diploid wheat accessions, 1% resistant T. boeoticum accessions and 16% susceptible T. monococcum accessions were found. In the present study these atypical accessions were compared with 49 typical T. monococcum, T. boeoticum and T. urartu accessions to gain insight into the host-status of the diploid wheat species for wheat leaf rust. Cluster analysis of morphological data and AFLP fingerprints of the typical accessions clearly discriminated the three diploid species. T. monococcum and T. boeoticum had rather-similar AFLP fingerprints while T. urartu had a very different fingerprint. The clustering of most atypical accessions was not consistent with the species they were assigned to, but intermediate between T. boeoticum and T. monococcum. Only four susceptible T. monococcum accessions were morphologically and moleculary similar to the typical T. monococcum accessions. Results confirmed that T. boeoticum and T. monococcum are closely related but indicate a clear difference in host-status for the wheat leaf rust fungus in these two species. Received: 7 November 2000 / Accepted: 31 March 2001     

Transferable bread wheat EST-SSRs can be useful for phylogenetic studies among the Triticeae species

The genetic similarity between 150 accessions, representing 14 diploidand polyploid species of the Triticeae tribe, was investigated following the UPGMA clustering method. Seventy-three common wheat EST-derived SSR markers (EST-SSRs) that were demonstrated to be transferable across several wheat-related species were used. When diploid species only are concerned, all the accessions bearing the same genome were clustered together without ambiguity while the separation between the different sub-species of tetraploid as well as hexaploid wheats was less clear. Dendrograms reconstructed based on data of 16 EST-SSRs mapped on the A genome confirmed that Triticum aestivum and Triticum durum had closer relationships with Triticum urartu than with Triticum monococcum and Triticum boeoticum, supporting the evidence that T. urartu is the A-genome ancestor of polyploid wheats. Similarly, another tree reconstructed based on data of ten EST-SSRs mapped on the B genome showed that Aegilops speltoides had the closest relationship with T. aestivum and T. durum, suggesting that it was the main contributor of the B genome of polyploid wheats. All these results were expected and demonstrate thus that EST-SSR markers are powerful enough for phylogenetic analysis among the Triticeae tribe.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Comparative and evolutionary analysis of new variants of ω-gliadin genes from three A-genome diploid wheats

A genomic polymerase chain reaction (PCR) cloning strategy was applied to isolate ω-gliadin sequences from three A-genome diploid wheats (Triticum monococcum, T. boeoticum and T. urartu). Amplicon lengths varied from 744 and 1,044 bp, and those of the corresponding deduced mature proteins from 248 to 348 residues. The primary structure of the deduced polypeptides comprised a short N- and C-terminal conserved domain, and a long, variable repetitive domain. A phylogenetic analysis recognised several clades: the first consisted of three T. aestivum sequences; the second and the third two T. boeoticum and six T. monococcum sequences; and the rest four T. urartu and three T. aestivum sequences. Among the functional (non-pseudogene) ARQ/E-type ω-gliadin sequences, two were derived from T. boeoticum and three from T. monococcum; one of the latter sequences appeared to be a chimera originating via illegitimate recombination between the other two T. monococcum sequences. None of the 12 intact ω-gliadin sequences contained any cysteine or methionine residues. We discussed the variation and evolution of A-genome ω-gliadin genes.     

Isozyme variation in some populations of wild diploid wheats in Iran

Isozyme electrophoresis data of seed extracts from 11 populations of diploid wheat species (Triticum boeoticum Bioss. and Triticum urartu Thumanian ex Gandilyan), distributed mainly in the western and west-northern Iran, were investigated. The five enzyme systems used were peroxidase, polyphenol oxidase, superoxide dismutase, malate dehydrogenase and catalase. The first three were found to be useful as molecular marker for characterization of diploid wheat populations. A total of 13 bands from three enzyme systems were recorded. The value of a ‘Jaccard's’ similarity coefficient ranges from 0.333 to 1.000. Data analysis was done using clustering method UPGMA. On the basis of Jaccard's coefficient, the obtained dendrogram supports previous relationship between T. boeoticum and T. urartu as separate species as well as reflecting their distinct gene pools and substantiating their specific recognition despite the overall morphological similarity.     

NADP-dependent aromatic alcohol dehydrogenase in polyploid wheats and their diploid relatives. On the origin and phylogeny of polyploid wheats

Summary The three major isoenzymes of the NADP-dependent aromatic alcohol dehydrogenase (ADH-B), distinguished in polyploid wheats by means of polyacrylamide gel electrophoresis, are shown to be coded by homoeoalleles of the locus Adh-2 on short arms of chromosomes of the fifth homoeologous group. Essentially codominant expression of the Adh-2 homoeolleles of composite genomes was observed in young seedlings of hexaploid wheats (T. aestivum s.l.) and tetraploid wheats of the emmer group (T. turgidum s.l.), whereas only the isoenzyme characteristic of the A genome is present in the seedlings of the timopheevii-group tetraploids (T. timopheevii s.str. and T. araraticum).The slowest-moving B³ isoenzyme of polyploid wheats, coded by the homoeoallele of the B genome, is characteristic of the diploid species Aegilops speltoides S.l., including both its awned and awnless forms, but was not encountered in Ae. bicornis, Ae. sharonensis and Ae. longissima. The last two diploids, as well as Ae. tauschii, Ae. caudata, Triticum monococcum s.str., T. boeoticum s.l. (incl. T. thaoudar) and T. urartu all shared a common isoenzyme coinciding electrophoretically with the band B² controlled by the A and D genome homoeoalleles in polyploid wheats. Ae. bicomis is characterized by the slowest isoenzyme, B⁴, not found in wheats and in the other diploid Aegilops species studied.Two electrophoretic variants of ADH-B, B¹ and B², considered to be alloenzymes of the A genome homoeoallele, were observed in T. dicoccoides, T. dicoccon, T. turgidum. s.str. and T. spelta, whereas B² was characteristic of T. timopheevii s.l. and only B¹ was found in the remaining taxa of polyploid wheats. The isoenzyme B¹, not encountered among diploid species, is considered to be a mutational derivative which arose on the tetraploid level from its more ancestral form B² characteristic of diploid wheats.The implication of the ADH-B isoenzyme data to the problems of wheat phylogeny and gene evolution is discussed.     

HYBRIDIZATION IN THE GENUS GLYCINE SUBGENUS GLYCINE WILLD. (LEGUMINOSAE,PAPILIONOIDEAE)

The genus Glycine is composed of two subgenera, Glycine and Soja. Soja includes the cultivated soybean, G. max, and its wild annual counterpart G. soja, while Glycine includes seven wild perennial species. Hybridization was carried out within and between wild perennial species of the subgenus Glycine. The success rate (pods set/flowers crossed) was 11% for intraspecific and 8% for interspecific crosses. A total of 220 F₁ hybrids was examined morphologically and cytologically where possible. Hybrids within G. canescens (2n = 40) and G. latifolia (2n = 40) were fertile as expected. Glycine clandestina (2n = 40) was morphologically separable into at least three groups, which produced fertile hybrids within each group. One cross between two groups gave vegetatively vigorous but sterile hybrids. The majority of crosses within G. tabacina (2n = 80) were fertile, except that extremely narrow-leaved forms gave sterile hybrids in combination with more usual forms. Sterility was also encountered in G. tomentella when aneuploids (2n = 78) from New South Wales, Australia, were crossed with tetraploids (2n = 80) from either Queensland, Australia, or Taiwan; crosses between the latter two populations resulted in seedling lethality. Cytological behavior of sterile hybrids followed a similar pattern, whether at the diploid or tetraploid level. The frequency of chromosome pairing was approximately half that expected if genomes showed full pairing homology. Bivalent disjunction at anaphase I was usually followed by precocious division of the majority of univalents. Telophase I and II were characterized by lagging chromosomes and micronuclei, so that resulting pollen was misshapen and sterile. Chromosome pairing data from sterile intraspecific hybrids at the tetraploid level may indicate a polyphyletic origin of tetraploids, whereby different diploid populations were involved in their formation. Similarly, chromosome pairing in sterile intraspecific diploid hybrids may indicate that the various diploid groups arose independently of one another. Both 40- and 80-chromosome forms are fully diploidized, however, and if they are of ancient origin, divergence since that time could have resulted in the chromosomal differentiation which becomes apparent when intraspecific hybridization is effected. Diploid (2n = 40) interspecific hybrids G. falcata × G. canescens, and G. falcata × G. tomentella grew poorly and did not reach flowering stage. Diploid (2n = 40) crosses between G. latifolia and G. tomentella produced inviable seedlings. Tetraploid (2n = 80) hybrids between G. tomentella and G. tabacina were vegetatively vigorous but sterile owing to low chromosome pairing at meiosis, indicating little pairing homology between the two species. Diploid hybrids between G. canescens and G. clandestina, however, showed almost complete chromosome pairing at diakinesis and partial fertility. Although morphologically distinct, these two species have not diverged sufficiently to prevent hybridization and possible gene exchange through recombination. Self compatibility, perennial growth habit, and geographic isolation have favored divergence among Glycine populations to the point that gene exchange appears no longer possible in many cases. Internal isolating mechanisms have been shown to operate at various levels of plant development from hybrid lethality at seedling stage, to failure of seed-set in sterile but vegetatively vigorous hybrids.     

Phylogeny of the a genomes of wild and cultivated wheat species

Diploid species of the genus Triticum L. are its most ancient representatives and have the A genome, which was more recently inherited by all polyploid species. Studies of the phylogenetic relationships among diploid and polyploid wheat species help to identify the donors of elementary genomes and to examine the species specificity of genomes. In this study, molecular analysis of the variable sequences of three nuclear genes (Acc-1, Pgk-1, and Vrn-1) was performed for wild and cultivated wheat species, including both diploids and polyploids. Based on the sequence variations found in the genes, clear differences were observed among elementary genomes, but almost no polymorphism was detected within each genome in polyploids. At the same time, the regions of the three genes proved to be rather heterogeneous in the diploid species Triticum boeoticum Boiss., T. urartu Thum. ex Gandil., and T. monococcum L., thus representing mixed populations. A genome variant identical to the A genome of polyploid species was observed only in T. urartu. Species-specific molecular markers discriminating the diploid species were not found. Analysis of the inheritance of morphological characters also failed to identify a species-specific character for the three diploid wheat species apart from the hairy leaf blade type, described previously.     

SEED PROTEIN PROFILES AND THE ORIGIN OF THE HEXAPLOID WHEATS

Protein profiles of Triticum and Aegilops species were obtained by electrophoresis of crude seed extracts on polyacrylamide gels. All subspecies of the hexaploid T. aestivum (AABBDD) showed a very uniform profile that could be closely simulated only by the pattern produced by a protein mixture (2:1) from specific profile types of the ancient tetraploid cultivar T. dicoccum (AABB) and the wild diploid Ae. squarrosa (DD). An exceptional hexaploid pattern occurred only in some accessions of T. aestivum ssp. macha. These results confirm the parentage of the aestivum hexaploids in general as T. dicoccum and Ae. squarrosa and more specifically identify the type of the D-genome donor. They suggest that these wheats, excepting the aberrant macha types, had essentially a monophyletic origin in southwestern Asia. They favor the hypotheses that the cultivated aestivum wheats were derived from the so-called primitive spelta complex primarily by mutation of a single gene governing the free threshing character and that alpine spelta represents an element displaced from the area of endemism.     

Can Triticum urartu (Poaceae) be identified by pollen analysis? Implications for detecting the ancestor of the extinct two‐grained einkorn‐like wheat

The domestication of the one‐grained einkorn (Triticum monococcum) in the Near East is relatively well known. However, an independent two‐grained einkorn‐like domestication has been archaeobotanically detected and scarce information is available. Triticum urartu, a wild wheat, was not fully described until the 1970s because the phenology does not allow it to be distinguished easily from wild einkorn (Triticum boeoticum subsp. thaoudar), although a genetic separation exists. Both species are mostly two grained and could potentially be the relatives of the extinct two‐grained form. Pollen grains of several genetically well‐identified wheat species, including T. urartu and T. boeoticum subsp. thaoudar, were studied by measuring the grain diameter and examining the exine sculpturing with phase‐contrast microscopy and scanning electron microscopy to gain an insight into differences enabling taxonomic identification. This work showed that, although T. urartu pollen is smaller on average, grain diameter is not sufficient because of the size overlap between the species, but T. urartu presents a different exine sculpturing (scabrate) from other Triticum spp. (aerolate). This outcome is useful for taxonomists and archaeobotanists. First, it will allow a simple re‐classification of herbarium materials. Second, further research could establish whether T. urartu was cultivated. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 278–289.