Distribution and characterization of Aegilops and Triticum species from the Bulgarian Black Sea coast

A total of 158 Aegilops-Triticum samples representing six Aegilops species (one diploid, four tetraploid and one hexaploid) and one diploid Triticum were collected along the Bulgarian Black Sea coast, and their distribution on the 350 km long coastal line was reported. The region south of Kamchia river, accepted as the middle point of the coast, was characterized by the greatest diversity of these wild relatives of wheat. The most widely distributed species in this area was Ae. geniculata. Ae. cylindrica was distributed only in north (Durankulak), while Ae. biuncialis and Ae. triuncialis were collected both north and south of Kamchia river. All samples of Ae. neglecta were hexaploid. Natural hybrids of goatgrass and wheat were found in Ae. cylindrica populations. Triticum monococcum ssp. aegilopoides had limited distribution in the south region. Aegilops uniaristata was recorded as a new species for the Bulgarian flora. Most of the samples expressed resistance to powdery mildew in seedling and adult stage, but all of them were polymorphic regarding the resistance to leaf rust (cultures 73760 and 43763). The study revealed additional data for the distribution of Aegilops and Triticum species in Bulgaria and their potential value as genetic resources in wheat improvement.     

A chromosome-specific sequence common to the B genome of polyploid wheat and Aegilops searsii

A low-copy, non-coding chromosome-specific DNA sequence, isolated from common wheat, was physically mapped to the distal 19% region of the long arm of chromosome 3B (3BL) of common wheat. This sequence, designated WPG118, was then characterized by Southern hybridization, PCR amplification and sequence comparison using a large collection of polyploid wheats and diploid Triticum and Aegilops species. The data show that the sequence exists in all polyploid wheats containing the B genome and absent from those containing the G genome. At the diploid level, it exists only in Ae. searsii, a diploid species of section Sitopsis, and not in other diploids including Ae. speltoides, the closest extant relative to the donor of the B genome of polyploid wheat. This finding may support the hypothesis that the B-genome of polyploid wheat is of a polyphyletic origin, i.e. it is a recombined genome derived from two or more diploid Aegilops species.     

Syntenic Relationships between the U and M Genomes of Aegilops,Wheat and the Model Species Brachypodium and Rice as Revealed by COS Markers

Diploid Aegilops umbellulata and Ae. comosa and their natural allotetraploid hybrids Ae. biuncialis and Ae. geniculata are important wild gene sources for wheat. With the aim of assisting in alien gene transfer, this study provides gene-based conserved orthologous set (COS) markers for the U and M genome chromosomes. Out of the 140 markers tested on a series of wheat-Aegilops chromosome introgression lines and flow-sorted subgenomic chromosome fractions, 100 were assigned to Aegilops chromosomes and six and seven duplications were identified in the U and M genomes, respectively. The marker-specific EST sequences were BLAST-ed to Brachypodium and rice genomic sequences to investigate macrosyntenic relationships between the U and M genomes of Aegilops, wheat and the model species. Five syntenic regions of Brachypodium identified genome rearrangements differentiating the U genome from the M genome and from the D genome of wheat. All of them seem to have evolved at the diploid level and to have been modified differentially in the polyploid species Ae. biuncialis and Ae. geniculata. A certain level of wheat–Aegilops homology was detected for group 1, 2, 3 and 5 chromosomes, while a clearly rearranged structure was showed for the group 4, 6 and 7 Aegilops chromosomes relative to wheat. The conserved orthologous set markers assigned to Aegilops chromosomes promise to accelerate gene introgression by facilitating the identification of alien chromatin. The syntenic relationships between the Aegilops species, wheat and model species will facilitate the targeted development of new markers specific for U and M genomic regions and will contribute to the understanding of molecular processes related to allopolyploidization.     

Comparative germination responses to water potential across different populations of Aegilops geniculata and cultivar varieties of Triticum durum and Triticum aestivum

• Crop Wild Relatives are often used to improve crop quality and yields because they contain genetically important traits that can contribute to stress resistance and adaptation.
• Seed germination of different populations of Aegilops geniculata Roth collected along a latitudinal gradient was studied under different drought stress in order to find populations suitable for improving drought tolerance in wheat. Different accessions of Aegilops neglecta Req. ex Bertol., Triticum aestivum L. and T. durum Desf. were used as comparison.
• Under full hydration, germination was high in all populations, but increasing drought stress led to reduced and delayed germination. Significant differences in final germination and mean time to germinate were detected among populations. Wheat, durum wheat and the southern population of Ae. geniculata were not significantly affected by drought stress, germinating similarly under all treatments. However, seed germination of the northern populations of Ae. geniculata was significantly reduced under high water stress treatment. Differences between populations of the same species could not be explained by annual rainfall across populations’ distributions, but by rainfall during seed development and maturation.
• Differences in the germination responses to drought found here highlight the importance of source populations as criteria for genotype selection for pre‐breeders.

     

Association between simple sequence repeat-rich chromosome regions and intergenomic translocation breakpoints in natural populations of allopolyploid wild wheats

Background and Aims

Repetitive DNA sequences are thought to be involved in the formation of chromosomal rearrangements. The aim of this study was to analyse the distribution of microsatellite clusters in Aegilops biuncialis and Aegilops geniculata, and its relationship with the intergenomic translocations in these allotetraploid species, wild genetic resources for wheat improvement.

Methods

The chromosomal localization of (ACG)_n and (GAA)_n microsatellite sequences in Ae. biuncialis and Ae. geniculata and in their diploid progenitors Aegilops comosa and Aegilops umbellulata was investigated by sequential in situ hybridization with simple sequence repeat (SSR) probes and repeated DNA probes (pSc119·2, Afa family and pTa71) and by dual-colour genomic in situ hybridization (GISH). Thirty-two Ae. biuncialis and 19 Ae. geniculata accessions were screened by GISH for intergenomic translocations, which were further characterized by fluorescence in situ hybridization and GISH.

Key Results

Single pericentromeric (ACG)_n signals were localized on most U and on some M genome chromosomes, whereas strong pericentromeric and several intercalary and telomeric (GAA)_n sites were observed on the Aegilops chromosomes. Three Ae. biuncialis accessions carried 7U^b–7M^b reciprocal translocations and one had a 7U^b–1M^b rearrangement, while two Ae. geniculata accessions carried 7U^g–1M^g or 5U^g–5M^g translocations. Conspicuous (ACG)_n and/or (GAA)_n clusters were located near the translocation breakpoints in eight of the ten translocated chromosomes analysed, SSR bands and breakpoints being statistically located at the same chromosomal site in six of them.

Conclusions

Intergenomic translocation breakpoints are frequently mapped to SSR-rich chromosomal regions in the allopolyploid species examined, suggesting that microsatellite repeated DNA sequences might facilitate the formation of those chromosomal rearrangements. The (ACG)_n and (GAA)_n SSR motifs serve as additional chromosome markers for the karyotypic analysis of UM genome Aegilops species.     

Analysis of metaphase I chromosome association in species of the genus Aegilops

Summary Metaphase-I chromosome associations in every diploid and polyploid species of the genus Aegilops were studied using C-banding in order to analyse the cytogenetic behaviour of the whole complement as well as of specific genomes in different polyploid species. Differences were observed in the frequency of associations per cell among different species of the same ploidic level and even between species sharing the same genomic constitution. Differences were also found between different genomes within the same polyploid species and between the same genome when present in several diploid and polyploid species. Several factors proposed as having an influence on the frequency of metaphase-I associations, such as chromosome morphology, C-heterochromatin content, genetic control and genome interactions, are discussed. Most of the polyploid Aegilops species showed a diploid-like behaviour at metaphase I although multivalents involving homoeologous associations were occasionally observed in Ae. biuncialis, Ae. juvenalis and Ae. crassa(6x); therefore, the Aegilops diploidising genetic system is not equally effective in all polyploid species.     

Genome differentiation in Aegilops. 4. Evolution of the U-genome cluster

Phylogenetic relationships of polyploid Aegilops species sharing the U-genome were investigated by analyzing heterochromatin banding patterns of their somatic metaphase chromosomes as revealed by C-banding and fluorescence in situ hybridization (FISH) with the heterochromatin-limited repetitive DNA probes pSc119, pAs1, as well as the distribution of NOR and 5S DNA loci revealed by pTa71 (18S-26S rDNA), and pTa794 (5S rDNA) probes. Seven tetraploid (Ae. triuncialis, Ae. peregrina, Ae. kotschyi, Ae. geniculata, Ae. biuncialis, Ae. columnaris, and 4x Ae. neglecta) and one hexaploid (6x Ae. neglecta) Aegilops species of the U-genome cluster were studied. The U^t and C^t chromosomes of 4x Ae. triuncialis (U^tC^t) were similar to the diploid donors Ae. umbellulata (U) and Ae. caudata (C). However, the size of the NOR locus on chromosome 5U^t was reduced. Karyotypic analyses confirmed that 4x Ae. peregrina (S^pU^p) was derived from a hybridization of the diploid species Ae. umbellulata with Ae. longissima, whereas Ae. umbellulata and Ae. sharonensis (or an immediate precursor) were the diploid progenitor species of Ae. kotschyi (S^kU^k). In both 4x species, the NORs on S-genome chromosomes were inactivated and were accompanied with a decrease or loss of rDNA sequences. Karyotypes of the tetraploid species, Ae. geniculata (U^gM^g) and Ae. biuncialis (U^bM^b) differed from each other and from the putative diploid progenitors Ae. umbellulata and Ae. comosa indicating that various types of chromosomal alterations occurred during speciation. Inactivation of major NORs on the M-genome chromosomes, redistribution of 5S rDNA sites, and loss of some minor 18S-26S rDNA loci were observed in Ae. geniculata and Ae. biuncialis. Significant differences in the total amount and distribution of heterochromatin, the number and location of 5S and 18S-26S rDNA loci observed between Ae. columnaris (U^cX^c)/4x Ae. neglecta (UⁿXⁿ) and Ae. geniculata/Ae. biuncialis indicate that these species have different origins. Similarities in C-banding and FISH patterns of most Ae. columnaris and 4x Ae. neglecta chromosomes suggest that they were probably derived from a common ancestor, whereas distinct differences of three chromosome pairs may indicate that the divergence of these species was probably associated with chromosomal rearrangements and/or introgressive hybridization. Ae. umbellulata contributed the U genome, however, the source of their second genomes remains unknown. The formation of 6x Ae. neglecta (UⁿXⁿNⁿ) was not associated with large modifications of the parental genomes.     

RAPD analysis of the intraspecific and interspecific variation and phylogenetic relationships of <Emphasis Type="Italic">Aegilops</Emphasis> L. species with the U genome

RAPD analysis was used to study the genetic variation and phylogenetic relationships of polyploid Aegilops species with the U genome. In total, 115 DNA samples of eight polyploid species containing the U genome and the diploid species Ae. umbellulata (U) were examined. Substantial interspecific polymorphism was observed for the majority of the polyploid species with the U genome (interspecific differences, 0.01–0,2; proportion of polymorphic loci, 56.6–88.2%). Aegilops triuncialis was identified as the only alloploid species with low interspecific polymorphism (interspecific differences, 0–0.01, P = 50%) in the U-genome group. The U-genome Aegilops species proved to be separated from other species of the genus. The phylogenetic relationships were established for the U-genome species. The greatest separation within the U-genome group was observed for the US-genome species Ae. kotschyi and Ae. variabilis. The tetraploid species Ae. triaristata and Ae. columnaris, which had the UX genome, and the hexaploid species Ae. recta (UXN) were found to be related to each other and separate from the UM-genome species. A similarity was observed between the UM-genome species Ae. ovata and Ae. biuncialis, which had the UM genome, and the ancestral diploid U-genome species Ae. umbellulata. The UC-genome species Ae. triuncialis was rather separate and slightly similar to the UX-genome species.     

An immunochemical approach to species relationship in Triticum and some related species

Summary An immunological reaction, precipitation in gel, was produced using a rabbit antiserum directed to a specific protein constantly present in bread wheats (T. aestivum, genome AABBDD), but absent in durum wheat (T. durum Desf., genome AABB). This protein was isolated in the soluble-protein fraction of bread wheat caryopses by combined biochemical and immunological techniques.The availability of such a specific anti-bread wheat serum made possible the analysis of a series of varieties and species of wheat and of some closely related (Secale, Aegilops) and less closely related (Hordeum, Haynaldia) taxa to determine whether the protein was present or absent. Hordeum vulgare, Haynaldia villosa, Triticum monoccocum and Triticum turgidum gave a negative result, while positive results were obtained in T. aestivum, T. timopheevi, T. zhukovskyi, Secale cereale, Aegilops speltoides, Ae. mutica, Ae. comosa, Ae. caudata, Ae. umbellulata, Ae. squarrosa, and also in the artificial amphiploids (Ae. speltoides x T. monococcum) and (Ae. caudata x T. monococcum).It is concluded that these results agree closely with the classification of Triticum proposed by MacKey in 1966. The investigated protein not only permits the differentiation of T. aestivum from T. turgidum, but also T. turgidum from T. timopheevi at tetraploid level and T. monococcum from all the diploid species of Aegilops.     

Amylase protein inhibitors and the role of Aegilops species in polyploid wheat speciation

Protein inhibitors extracted with water from seeds of Triticum and genetically related species were characterized according to their apparent molecular weights, electrophoretic mobilities and their specificities in inhibiting α-amylases from human saliva and Tenebrio molitor L. larvae. No detectable amylase inhibition activity was found in extracts from diploid wheats, whereas in all tetraploid and hexaploid wheats as well as in the Aegilops species tested we found several amylase inhibitor groups of different molecular weights. In each group, several inhibitor components slightly different in their electrophoretic mobilities, but identical in their inhibition behaviour toward amylases from different origins have been shown. Both from the qualitative and quantitative standpoints, amylase protein inhibitors from hexaploid wheats were the summation of those from tetraploid wheats plus the ones from Aegilops squarrosa. Amylase inhibitors from Aegilops speltoides largely differed from those extracted from tetraploid wheats as well as from all the amylase inhibitors described in plant seeds up to now. These results indicate a relevant homology between the amylase inhibitor coding genes of the D wheat genome and those of the D Aegilops genome and confirm that Ae. squarrosa is the donor of the whole D genome to hexaploid wheats. They also suggest that Ae. speltoides is not the donor of the B genome to polyploid wheats, although a not yet identified Aegilops species might be such a donor.     

Species relationships and genetic variation in the diploid wheats (Triticum,Aegilops) as revealed by starch gel electrophoresis

Twenty enzyme loci were examined in the diploid species ofTriticum andAegilops for allelic variation by starch gel electrophoresis. SectionSitopsis, including the five species,Ae. speltoides, Ae. lingissima, Ae. sharonensis, Ae. bicornis andAe. searsii form a close subgroup withAe. speltoides slightly removed from the others.T. monococcum s. lat., was found to be closest to the species of theSitopsis group.Ae. comosa, Ae. umbellulata andAe. uniaristata form a second subgroup withAe. caudata most closely related to these species.Ae. squarrosa appears almost equally related to all of the species, showing no special affinity for any one species group. Nineteen out of twenty loci examined were polymorphic with a mean of 6.7 alleles per locus. Species could be, for most loci, characterized by the presence of predominant alleles. A conspicious genetic characteristic ofTriticum-Aegilops is the sharing of these predominant alleles between species. Within species variation is characterized by a diffuse distribution of secondary alleles.     

Characterization of genetic variation in and phylogenetic relationships among diploid<Emphasis Type="Italic"> Aegilops</Emphasis> species by AFLP: incongruity of chloroplast and nuclear data

Intra- and inter-specific genetic variation was investigated in seven diploid Aegilops species using the amplified fragment length polymorphism (AFLP) technique. Of the seven species, the cross-pollinating Aegilops speltoides and Aegilops mutica showed high levels of intraspecific variation whereas the remaining five self-pollinating species showed low levels. Aegilops bicornis, Aegilops searsii and Ae. speltoides formed one cluster in the dendrograms, while Aegilops caudata and Aegilops umbellulata formed another. Relationships among the species inferred were more consistent with the relationships inferred from studies of chromosome pairing in interspecific hybrids, and previous molecular phylogenetic reconstructions based on nuclear DNA, than they were with those based on molecular plasmon analysis, suggesting that the nuclear genome has evolved differently from the cytoplasmic genome in the genus Aegilops.Communicated by J. Dvorak     

On the diploidization mechanism of the genus Aegilops: meiotic behaviour of interspecific hybrids

Chromosomal pairing of the three diploid hybrids Aegilops uniaristata × Ae. tauschii (ND), Ae. umbellulata × Ae. tauschii (UD) and Ae. comosa × Ae. uniaristata (MN), and a triploid hybrid Ae. cylindrica × Ae. caudata (DCC), was analyzed by electron microscopy in surface-spread-prophase-I nuclei and compared with light-microscopic observations of metaphase-I cells after C-banding and fluorescence in situhybridization. All hybrids showed extensive synapsis and complex multivalents in which up to 14 chromosomes were involved. In the diploid hybrids most metaphase-I chromosomal associations were between homoeologs, their frequencies being dependent on the relationship between the donor genomes. Despite the different overall bound-arm frequencies displayed by ND and MN hybrids at metaphase-I, chromosomes bearing rDNA sequences showed similar mean cell chromosomal association frequencies. In the triploid hybrid preferential associations involving C genomes were predominant. These observations are discussed in relation to the mechanism of diploidization showed by allotetraploid Aegilops species. Received: 13 January 1999 / Accepted: 12 March 1999     

Atrazine-resistant cytoplasmic male-sterile-nigra broccoli obtained by protoplast fusion between cytoplasmic male-sterile Brassica oleracea and atrazine-resistant Brassica campestris

Summary By using restriction endonuclease digestion patterns, the degree of intraspecific polymorphism of mitochondrial DNA in four diploid species of wheat and Aegilops, Ae. speltoides, Ae. longissima, Ae. squarrosa, and Triticum monococcum, was assessed. The outbreeding Ae. speltoides was found to possess the highest degree of variability, the mean number of nucleotide substitutions among conspecific individuals being 0.027 substitutions per nucleotide site. A very low degree of mtDNA variation was detected among Ae. longissima accessions, with most of the enzyme-probe combinations exhibiting uniform hybridization patterns. The mean number of substitutions among Ae. longissima individuals was 0.001 substitutions per nucleotide site. The domesticated diploid wheat T. monococcum var. monococcum and its conspecific variant T. monococcum var. boeoticum seem to lack mitochondrial DNA variability altogether. Thus, the restriction fragment pattern can be used as a characteristic identifier of the T. monococcum cytoplasmic genome. Similarly, Ae. squarrosa accessions were found to be genetically uniform. A higher degree of variation among accessions is observed when noncoding sequences are used as probes then when adjacent coding regions are used. Thus, while noncoding regions may contain regulatory functions, they are subject to less stringent functional constraints than protein-coding regions. Intraspecific variation in mitochondrial DNA correlates perfectly with the nuclear variability detected by using protein electrophoretic characters. This correlation indicates that both types of variation are selectively neutral and are affected only by the effective population size.     

Electrophoretic and molecular analysis of alpha-gliadins inAegilops species (Poaceae) belonging to the D genome cluster and in their putative progenitors

The D genome cluster includes six allopolyploidAegilops species having as pivotal genome that ofAegilops squarrosa. Alpha-gliadins, endosperm proteins coded by multigenic families, have been analyzed in the D genome species cluster and in their putative progenitors. They can be present or weakly expressed when analyzed in acid polyacrylamide gel electrophoresis. Molecular analysis has shown the possibility to distinguish subsp.strangulata from subsp.eusquarrosa and to confirm the presence ofAe. caudata and ofAe. umbellulata in the polyploidsAe. cylindrica andAe. juvenalis, respectively. Finally, introgression fromAe. longissima orAe. searsii in tetraploid and hexaploidAe. crassa, Ae. juvenalis, andAe. vavilovii is supposed.     

Phylogenetic Relationships and Intraspecific Variation of D-Genome Aegilops L. as Revealed by RAPD Analysis

RAPD analysis was carried out to study the genetic variation and phylogenetic relationships of polyploid Aegilops species, which contain the D genome as a component of the alloploid genome, and diploid Aegilops tauschii, which is a putative donor of the D genome for common wheat. In total, 74 accessions of six D-genome Aegilops species were examined. The highest intraspecific variation (0.03–0.21) was observed for Ae. tauschii. Intraspecific distances between accessions ranged 0.007–0.067 in Ae. cylindrica, 0.017–0.047 in Ae. vavilovii, and 0–0.053 inAe. juvenalis.Likewise, Ae. ventricosaand Ae. crassa showed low intraspecific polymorphism. The among-accession difference in alloploidAe. ventricosa (genome D^vN^v) was similar to that of one parental species, Ae. uniaristata (N), and substantially lower than in the other parent, Ae. tauschii (D). The among-accession difference in Ae. cylindrica(C^cD^c) was considerably lower than in either parent, Ae. tauschii (D) orAe. caudata (C). With the exception of Ae. cylindrica, all D-genome species—Ae. tauschii (D),Ae. ventricosa (D^vN^v), Ae. crassa (X^crD^cr1 and X^crD^cr1D^cr2), Ae. juvenalis (X^jD^jU^j), andAe. vavilovii (X^vaD^vaS^va)—formed a single polymorphic cluster, which was distinct from clusters of other species. The only exception, Ae. cylindrica(C^cD^c), did not group with the other D-genome species, but clustered withAe. caudata (C), a donor of the C genome. The cluster of these two species was clearly distinct from the cluster of the other D-genome species and close to a cluster of Ae. umbellulata (genome U) and Ae. ovata (genome U^gM^g). Thus, RAPD analysis for the first time was used to estimate and to compare the interpopulation polymorphism and to establish the phylogenetic relationships of all diploid and alloploid D-genome Aegilops species.     

Electrophoretic survey of seedling esterases in wheats in relation to their phylogeny

Summary Evolutionary and ontogenetic variation of six seedling esterases of independent genetic control is studied in polyploid wheats and their diploid relatives by means of polyacrylamide gel electrophoresis. Four of them are shown to be controlled by homoeoallelic genes in chromosomes of third, sixth and seventh homoeologous groups.The isoesterase electrophoretic data are considered supporting a monophyletic origin of both the primitive tetraploid and the primitive hexaploid wheat from which contemporary taxa of polyploid wheats have emerged polyphyletically and polytopically through recurrent introgressive hybridization and accumulation of mutations. Ancestral diploids belonging or closely related to Triticum boeoticum, T. urartu, Aegilops speltoides and Ae. tauschii ssp. strangulata are genetically the most suitable genome donors of polyploid wheats. Diploids of the Emarginata subsection of the section Sitopsis, Aegilops longissima s.str., Ae. sharonensis, Ae. searsii and Ae. bicornis, are unsuitable for the role of the wheat B genome donors, being all fixed for the esterase B and D electromorphs different from those of tetraploid wheats.     

Salt tolerance potential of wild resources of the tribe Triticeae

The salt tolerance potential of variousAegilops species of different genome combinationsviz., Aegilops squarrosa, Ae. cylindrica, Ae. ovata. Ae. triuncialis, Ae. variabilis, Ae. bicornis, Ae. longissima, Ae. umbellulata, andAe. sharonensis was tested to identify the high salt-tolerant genotype(s). Screening was done in cement tanks filled with gravel and Hoagland nutrient solution. Salinity was created by mixing Na₂SO₄, CaCl₂, MgCl₂ and NaCl in the ratio of 10∶5∶1∶4 and induced by a stepwise increase in electrical conductivity number of tillers and number of leaves. Inter-and intragenomic variations for cation uptake were also significant. Species with DD and CD genome were found to be highly tolerant. Possible factors responsible for these observations have been discussed.     

Molecular characterization of novel low-molecular-weight glutenin genes inAegilops longissima

Extensive genetic variations of low-molecular-weight glutenin subunits (LMW-GS) and their coding genes were found in the wild diploid A- and D-genome donors of common wheat. In this study, we reported the isolation and characterization of 8 novel LMW-GS genes fromAe.longissima Schweinf. & Muschl., a species of the sectionSitopsis of the genusAegilops, which is closely related to the B genome of common wheat. Based on the N-terminal domain sequences, the 8 genes were divided into 3 groups. A consensus alignment of the extremely conserved domains with known gene groups and the subsequent cluster analysis showed that 2 out of the 3 groups of LMW-GS genes were closely related to those from the B genome, and the remaining was related to those from A and D genomes of wheat andAe. tauschii. Using 3 sets of gene-group-specific primers, PCRs in diploid, tetraploid and hexaploid wheats andAe. tauschii failed to obtain the expected products, indicating that the 3 groups of LMW-GS genes obtained in this study were new members of LMW-GS multi-gene families. These results suggested that theSitopsis species of the genusAegilops with novel gene variations could be used as valuable gene resources of LMW-GS. The 3 sets of group-specific primers could be utilized as molecular markers to investigate the introgression of novel alien LMW-GS genes fromAe. longissima into wheat.     

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.