Molecular characterisation of the amino- and carboxyl-domains in different Glu-A1x alleles of Triticum urartu Thum. ex Gandil.

The wild diploid wheat (Triticum urartu Thum. ex Gandil.) is a potential gene source for wheat breeding, as this species has been identified as the A-genome donor in polyploid wheats. One important wheat breeding trait is bread-making quality, which is associated in bread wheat (T. aestivum ssp. aestivum L. em. Thell.) with the high-molecular-weight glutenin subunits. In T. urartu, these proteins are encoded by the Glu-A1x and Glu-A1Ay genes at the Glu-A ^u 1 locus. The Glu-A1x genes of 12 Glu-A ^u 1 allelic variants previously detected in this species were analysed using PCR amplification and sequencing. Data showed wide diversity for the Glu-A1x alleles in T. urartu, which also showed clear differences to the bread wheat alleles. This variation could enlarge the high-quality genetic pool of modern wheat and be used to diversify the bread-making quality in durum (T. turgidum ssp. durum Desf. em. Husn.) and common wheat.     

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     

Genetic characterization and curation of diploid A-genome wheat species

A-genome diploid wheats represent the earliest domesticated and cultivated wheat species in the Fertile Crescent and include the donor of the wheat A sub-genome. The A-genome species encompass the cultivated einkorn (Triticum monococcum L. subsp. monococcum), wild einkorn (T. monococcum L. subsp. aegilopoides (Link) Thell.), and Triticum urartu. We evaluated the collection of 930 accessions in the Wheat Genetics Resource Center (WGRC) using genotyping by sequencing and identified 13,860 curated single-nucleotide polymorphisms. Genomic analysis detected misclassified and genetically identical (>99%) accessions, with most of the identical accessions originating from the same or nearby locations. About 56% (n = 520) of the WGRC A-genome species collections were genetically identical, supporting the need for genomic characterization for effective curation and maintenance of these collections. Population structure analysis confirmed the morphology-based classifications of the accessions and reflected the species geographic distributions. We also showed that T. urartu is the closest A-genome diploid to the A-subgenome in common wheat (Triticum aestivum L.) through phylogenetic analysis. Population analysis within the wild einkorn group showed three genetically distinct clusters, which corresponded with wild einkorn races α, β, and γ described previously. The T. monococcum genome-wide F_ST scan identified candidate genomic regions harboring a domestication selection signature at the Non-brittle rachis 1 (Btr1) locus on the short arm of chromosome 3A^m at ∼70 Mb. We established an A-genome core set (79 accessions) based on allelic diversity, geographical distribution, and available phenotypic data. The individual species core set maintained at least 79% of allelic variants in the A-genome collection and constituted a valuable genetic resource to improve wheat and domesticated einkorn in breeding programs.

Genotyping diploid A-genome relatives of wheat uncovered high genetic diversity and unique evolutionary relationships giving insight to the effective use of this germplasm for wheat improvement.     

Genetic control of the wheat Triticum monococcum L. resistance to powdery mildew

Using hybrid analysis and test-clone method, 102 accessions of Triticum monococcum L. from the collection of the Vavilov All-Russia Institute of Plant Industry have been studied. This species of wheat has been found to by considerably polymorphic with respect to the resistance to the fungus Erysiphe graminis DC. f. sp. tritici Marchal. causing powdery mildew. The resistance of most accessions to the fungus population and clones is determined by dominant genes. In rare cases, the resistance was determined by recessive genes or one, two, or three oligogenes. A group of einkorn wheat accessions has been found in which the resistance to powdery mildew was determined by the same dominant factor or different but closely linked ones. Recessive resistance genes of T. monococcum differ from the recessive gene pm5 determining the resistance of T. aestivum plants. The genome of T. monococcum contains various genes of resistance to powdery mildew and is a potential source of effective genes to be used when selecting cultivated species of wheat for immunity.     

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     

Exploring the diploid wheat ancestral A genome through sequence comparison at the high-molecular-weight glutenin locus region

The polyploid nature of hexaploid wheat (T. aestivum, AABBDD) often represents a great challenge in various aspects of research including genetic mapping, map-based cloning of important genes, and sequencing and accurately assembly of its genome. To explore the utility of ancestral diploid species of polyploid wheat, sequence variation of T. urartu (A^uA^u) was analyzed by comparing its 277-kb large genomic region carrying the important Glu-1 locus with the homologous regions from the A genomes of the diploid T. monococcum (A^mA^m), tetraploid T. turgidum (AABB), and hexaploid T. aestivum (AABBDD). Our results revealed that in addition to a high degree of the gene collinearity, nested retroelement structures were also considerably conserved among the A^u genome and the A genomes in polyploid wheats, suggesting that the majority of the repetitive sequences in the A genomes of polyploid wheats originated from the diploid A^u genome. The difference in the compared region between A^u and A is mainly caused by four differential TE insertion and two deletion events between these genomes. The estimated divergence time of A genomes calculated on nucleotide substitution rate in both shared TEs and collinear genes further supports the closer evolutionary relationship of A to A^u than to A^m. The structure conservation in the repetitive regions promoted us to develop repeat junction markers based on the A^u sequence for mapping the A genome in hexaploid wheat. Eighty percent of these repeat junction markers were successfully mapped to the corresponding region in hexaploid wheat, suggesting that T. urartu could serve as a useful resource for developing molecular markers for genetic and breeding studies in hexaploid wheat.     

Molecular characterisation of the Wx-B1 allelic variants identified in cultivated emmer wheat and comparison with those of durum wheat

Emmer wheat is a neglected crop that could be used in the breeding of modern durum wheat for quality, one important aspect of which is the starch composition that is related to the waxy proteins. A collection of 87 accessions of Spanish emmer wheat was analysed for waxy protein composition by SDS?CPAGE. No polymorphism was found for the Wx-A1 gene. However, for the Wx-B1 gene, three alleles were detected, two of them new. The whole gene sequence of these alleles was amplified by PCR in three fragments, which were digested with several endonucleases to determine internal differences in the sequence. These variants were also compared with the Wx alleles present in durum wheat. Differences in size and restriction sites were detected. DNA sequence analysis confirmed that the alleles found in emmer wheat are different from those in durum wheat. The first data suggested that these alleles showed a different influence on the amylose content of these lines. The variation found could be used to enlarge the gene pool of durum and emmer wheat, and design new materials with different amylose content.     

Molecular Characterization of the pina Gene in Einkorn Wheat

Fifty-six sequences encoding the pina protein were characterized from three species or subspecies of einkorn wheat. These sequences contained 1,595 nucleotides, including 1,270 conserved sites, 21 single nucleotide polymorphisms (SNPs), and 16 indels. The average frequency of SNPs and indels was one out of 76.1 and 99.9 bases, respectively. Five SNPs and no indels were found in the translated sequences. Fourteen haplotypes were defined, and the accessions in each haplotype ranged from 1 to 18. There were nine haplotypes in Triticum monococcum ssp. aegilopoides, eight in T. monococcum ssp. monococcum, and two in T. urartu. Phylogenetic analysis showed that pina genes from different species or subspecies could be clearly differentiated based on the open reading frame. Genes from T. urartu grouped together, whereas genes from T. monococcum ssp. aegilopoides and T. monococcum ssp. monococcum were shared by three and two clusters, respectively. Both the haplotype and phylogenetic analyses indicated that T. monococcum ssp. aegilopoides was more diverse. These results would contribute to the understanding of functional aspects and efficient utilization of pina genes.     

In vitro mature embryo culture protocol of einkorn (Triticum monococcum ssp. monococcum) and bread (Triticum aestivum L.) wheat under boron stress

Mature embryos of einkorn (Triticum monococcum ssp. monococcum) and bread (Triticum aestivum L.) wheat were used for callus induction on media containing four different doses (0, 1, 2 and 4 mg L^?1) of 2,4-D and dicamba supplemented with five different boron concentrations (0, 6.2, 12.4, 24.8, and 37.2 mg L^?1). The obtained callus was transferred to culture media with three (0, 0.5, and 2 mg L^?1) different BAP doses with five boron concentrations for further regeneration. The maximum callus weight in einkorn wheat was in culture media with 1 mg L^?1 dicamba and 6.2 mg L^?1 (3.71?±?0.13 g). Bread wheat had the maximum callus weight on culture media with 4 mg L^?1 dicamba and 12.4 mg L^?1 (3.46?±?0.40 g). The highest plantlet numbers were in only 2 mg L^?1 BAP (2.92?±?0.88) for einkorn wheat and 0.5 mg L^?1 BAP supplemented with 6.2 mg L^?1 boron (3.71?±?1.12) for bread wheat. This indirect regeneration protocol using mature embryos of einkorn and bread wheat under boron stresses expected to be useful for future wheat breeding studies.

     

Molecular characterization and diversity of the Pina and Pinb genes in cultivated and wild diploid wheat

Grain hardness is one of the most important characteristics of wheat quality. Soft endosperm is associated with the presence of two proteins in the wild form, puroindoline a and b. The puroindoline genes and their derived proteins are present in the putative wheat diploid ancestors which are thought to be the donors of the A, B and D genomes in common and durum wheat. In this study, we investigated the variability of grain hardness in einkorn, along with the nucleotide diversity of Pina and Pinb genes in a collection of einkorn wheat and T. urartu, in addition to studying the neutrality and linkage disequilibrium of these genes. Various alleles were detected for Pina and Pinb genes including three novel alleles for the Pinb locus: Pinb-A ^m 1i, Pinb-A ^m 1j and Pinb-A ^m 1k. Some differences were found in grain hardness between the different genotypes. The neutrality test showed a different pattern of variation between the two Pin genes. The genetic analysis of a diploid wheat collection has demonstrated that these species are a potential source of novel puroindoline variants. Our data suggest that, although further studies must be carried out, these variants could be used to expand the range of grain texture in durum and common wheat, which would permit the development of new materials adapted to novel uses in the baking and pasta industry.     

Mechanisms,origin and heredity of Glu-1Ay silencing in wheat evolution and domestication

Key message

Allotetraploidization drives Glu-1Ay silencing in polyploid wheat.

Abstract

The high-molecular-weight glutenin subunit gene, Glu-1Ay, is always silenced in common wheat via elusive mechanisms. To investigate its silencing and heredity during wheat polyploidization and domestication, the Glu-1Ay gene was characterized in 1246 accessions containing diploid and polyploid wheat worldwide. Eight expressed Glu-1Ay alleles (in 71.81% accessions) and five silenced alleles with a premature termination codon (PTC) were identified in Triticum urartu; 4 expressed alleles (in 41.21% accessions), 13 alleles with PTCs and 1 allele with a WIS 2-1A retrotransposon were present in wild tetraploid wheat; and only silenced alleles with PTC or WIS 2-1A were in cultivated tetra- and hexaploid wheat. Both the PTC number and position in T. urartu Glu-1Ay alleles (one in the N-terminal region) differed from its progeny wild tetraploid wheat (1–5 PTCs mainly in the repetitive domain). The WIS 2-1A insertion occurred?~?0.13 million years ago in wild tetraploid wheat, much later than the allotetraploidization event. The Glu-1Ay alleles with PTCs or WIS 2-1A that arose in wild tetraploid wheat were fully succeeded to cultivated tetraploid and hexaploid wheat. In addition, the Glu-1Ay gene in wild einkorn inherited to cultivated einkorn. Our data demonstrated that the silencing of Glu-1Ay in tetraploid and hexaploid wheat was attributed to the new PTCs and WIS 2-1A insertion in wild tetraploid wheat, and most silenced alleles were delivered to the cultivated tetraploid and hexaploid wheat, providing a clear evolutionary history of the Glu-1Ay gene in the wheat polyploidization and domestication processes.

     

Electrophoretic analysis of the high-molecular-weight glutenin subunits of Triticum monococcum,T. urartu,and the A genome of bread wheat (T. aestivum)

Summary The high molecular weight (HMW) subunit composition of glutenin was analysed by sodium dodecyl sulphate, polyacrylamide gel electrophoresis (SDS-PAGE) in the A genome of 497 diploid wheats and in 851 landraces of bread wheat. The material comprised 209 accessions of wild Triticum monococcum ssp. boeoticum from Greece, Turkey, Lebanon, Armenia, Iraq, and Iran; 132 accessions of the primitive domesticate T. monococcum ssp. monococcum from many different germplasm collections; one accession of free-threshing T. monococcum ssp. sinskajae; 155 accessions of wild T. urartu from Lebanon, Turkey, Armenia, Iraq, and Iran; and landraces of T. aestivum, mainly from the Mediterranean area and countries bordering on the Himalayan Mountains. Four novel HMW glutenin sub-units were discovered in the landraces of bread wheat, and the alleles that control them were designated Glu-Ald through Glu-Alg, respectively. The HMW subunits of T. monococcum ssp. boeoticum have a major, x subunit of slow mobility and several, less prominent, y subunits of greater mobility, all of which fall within the mobility range of HMW subunits reported for bread wheat. In T. monococcum ssp. monococcum the range of the banding patterns for HMW subunits was similar to that of ssp. boeoticum. However, two accessions, while containing y subunits were null for x subunits. The single accession of Triticum monococcum ssp. sinskajae had a banding pattern similar to that of most ssp. boeoticum and ssp. monococcum accessions. The HMW subunit banding patterns of T. urartu accessions were distinct from those of T. monococcum. All of them contained one major x and most contained one major y subunit. In the other accessions a y subunit was not expressed. The active genes for y subunits, if transferred to bread wheat, may be useful in improving bread-making quality.     

Molecular characterisation of two novel starch granule proteins 1 in wild and cultivated diploid A genome wheat species

Starch synthase IIa, also known as starch granule protein 1 (SGP-1), plays a key role in amylopectin biosynthesis. The absence of SGP-1 in cereal grains is correlated to dramatic changes in the grains’ starch content, structure, and composition. An extensive investigation of starch granule proteins in this study revealed a polymorphism in the electrophoretic mobility of SGP-1 between two species of wheat, Triticum urartu and T. monococcum; this protein was, however, conserved among all other Triticum species that share the A genome inherited from their progenitor T. urartu. Two different electrophoretic profiles were identified: SGP-A1 proteins of T. urartu accessions had a SDS–PAGE mobility similar to those of tetraploid and hexaploid wheat species; conversely, SGP-A1 proteins of T. monococcum ssp. monococcum and ssp. boeoticum accessions showed a different electrophoretic mobility. The entire coding region of the two genes was isolated and sequenced in an attempt to explain the polymorphism identified. Several single nucleotide polymorphisms (SNPs) responsible for amino acid changes were identified, but no indel polymorphism was observed to explain the difference in electrophoretic mobility. Amylose content did not differ significantly among T. urartu, T. monococcum ssp. boeoticum and T. monococcum ssp. monococcum, except in one accession of the ssp. boeoticum. Conversely, several interspecific differences were observed in viscosity properties (investigated as viscosity profiles using a rapid visco analyzer—RVA profiles) of these cereal grains. T. monococcum ssp. boeoticum accessions had the lowest RVA profiles, T. urartu accessions had an intermediate RVA profile, whereas T. monococcum ssp. monococcum showed the highest RVA profile. These differences could be associated with the numerous amino acid and structural changes evident among the SGP-1 proteins.     

Genetic transformation of einkorn (<Emphasis Type="Italic">Triticum monococcum L.</Emphasis> ssp. monococcum L.), a diploid cultivated wheat species

Background

Domesticated einkorn (Triticum monococcum L.) is one of the oldest cultivated cereal crops in the world. Its small genome size (~?5.7 GB), low ploidy (2n?=?2x?=?14, A^mA^m) and high genetic polymorphism make this species very attractive for use as a diploid model for understanding the genomics and proteomics of Triticeae. Einkorn, however, is still a recalcitrant monocotyledonous species for the application of modern biotechnologies, including transgenesis. This paper reports the factors that may influence transgene delivery, integration, expression and inheritance in einkorn.

Results

In this study, we report the successful genetic transformation of einkorn using biolistic-mediated DNA delivery. Immature embryo-derived tissues of spring einkorn were bombarded with a plasmid containing the reporter gene GFP (green fluorescent protein) driven by the rice actin promoter (act1) and the selectable bar gene (bialaphos resistance gene) driven by the maize ubiquitin promoter (ubi1). Adjustments to various parameters such as gas pressure, microcarrier size and developmental stage of target tissue were essential for successful transient and stable transformation. Bombarded einkorn tissues are recalcitrant to regenerating plants, but certain modifications of the culture medium have been shown to increase the production of transgenic events. In various experiments, independent transgenic plants were produced at frequencies ranging from 0.0 to 0.6%. Molecular analysis, marker gene expression and herbicide treatment demonstrated that gfp/bar genes were stably integrated into the einkorn genome and successfully inherited over several generations. The transgenes, as dominant loci, segregated in both Mendelian and non-Mendelian fashion due to multiple insertions. Fertile homozygous T₁-T₂ populations of transgenic einkorn that are resistant to herbicides were selected.

Conclusion

To the best of our knowledge, this is the first report of the production of genetically modified einkorn plants. We believe that the results of our research could be a starting point for the application of the current biotechnological-based technologies, such as transgenesis and genome editing, to accelerate comparative functional genomics in einkorn and other cereals.

     

Microsatellite Marker Linked to a Leaf Rust Resistance Gene from Triticum monococcum L Transferred to Bread Wheat

Triticum monococcum L, a diploid wheat species closely related to the A genome of cultivated wheats, is highly resistant to leaf rust. A synthetic amphiploid, T. monococcum — T. durum was crossed with T. aestivum cv WL711, highly susceptible to leaf rust. Leaf rust resistant derivatives were selected among backcross generations with the recurrent parent WL711 and cytologically analysed. Chromosome number of the leaf rust resistant BC₁F₃ progenies varied from 39 to 44. Six leaf rust resistant and susceptible bulks from different BC₁F₃ progenies were analysed using 29 wheat microsatellite(WMS) markers already mapped on A genome of bread wheat and found polymorphic among parents. One T. monococcum specific allele of WMS gwm136 locus was found to be closely linked to the leaf rust resistance gene in all the resistant bulks. Differential chromosome number, frequency of univalents and multivalents, however, indicated that the critical T. monococcum chromosome might be present in addition to the A genome chromosomes of wheat, substituted either for the B or D genome chromosome of wheat or translocated to chromosome 1A of wheat in one or the other bulks. The association of the T. monococcum specific allele of WMS gwm136 locus to leaf rust resistance was further confirmed from bulked segregant analysis in BC₂F₁ generation.     

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 two y-type high molecular weight glutenin subunit alleles 1Ay12 and 1Ay8 from cultivated einkorn wheat (Triticum monococcum ssp. monococcum)

Two y-type high molecular weight glutenin subunits (HMW-GSs) 1Ay12^? and 1Ay8^? from the two accessions PI560720 and PI345186 of cultivated einkorn wheat (Triticum monococcum ssp. monococcum, AA, 2n = 2x = 14), were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The mobility of 1Ay12^? and 1Ay8^? was similar to that of 1Dy12 and 1By8 from common wheat Chinese Spring, respectively. Their ORFs respectively consisted of 1812 bp and 1935 bp, encoding 602 and 643 amino acid residues with the four typical structural domains of HMW-GS including signal peptide, conserved N-, and C-terminal and central repetitive domains. Compared with the most similar active 1Ay alleles previous published, there were a total of 15 SNPs and 2 InDels in them. Their encoding functions were confirmed by successful heterogeneous expression. The two novel 1Ay alleles were named as 1Ay12^? and 1Ay8^? with the accession No. JQ318694 and JQ318695 in GenBank, respectively. The two alleles were classed into the two distinct groups, Phe-type and Cys-type, which might be relevant to the differentiation of Glu-A1-2 alleles. Of which, 1Ay8^? belonged to Cys-type group, and its protein possessed an additional conserved cysteine residue in central repetitive region besides the six common ones in N- and C-terminal regions of Phe-type group, and was the second longest in all the known active 1Ay alleles. These results suggested that the subunit 1Ay8^? of cultivated einkorn wheat accession PI345186 might have a potential ability to strengthen the gluten polymer interactions and be a valuable genetic resource for wheat quality improvement.     

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     

Assessment of the type and degree of restriction fragment length polymorphism (RFLP) in diploid species of the genus Triticum

The A genome of the Triticeae is carried by three diploid species and subspecies of the genus Triticum: T. monococcum ssp. monococcum, T. monococcum ssp. boeoticum, and T. urartu, the A-genome donor of bread wheat. These species carry many genes of agronomic interest, including disease resistances, and may also be used for the genetic mapping of the A genome. The aim of this study was to evaluate the variability present in a sample of 25 accessions representative of this group using RFLP markers. Twenty probes, consisting of genomic DNA or cDNA from wheat, were used in combination with four restriction enzymes. A high level of polymorphism was found, especially at the interspecific level. Selecting the most informative enzymes appeared to be of great importance in order to obtain a stable structure for the diversity observed with only 20 probes. The results are largely consistent with taxonomy and data relating to geographical origins. The probes were also tested on 14 wheat cutivars. A good correlation coefficient was found for their informative values on wheat cultivars and diploid lines. Whether the group of species studied here would be useful for genetic mapping remains to be determined. Nevertheless, RFLP markers will be useful to follow genes that can possibly be introgressed from these species into cultivated wheat.