Stripe rust resistance in <Emphasis Type="Italic">Aegilops tauschii</Emphasis> and its genetic analysis

Aegilops tauschii Coss., the D-genome progenitor of common wheat (Triticum aestivum L.) includes two subspecies, tauschii and strangulata (Eig) Tzvel. Subspecies tauschii has a wide geographic distribution spreading westwards to Turkey and eastwards to Afghanistan and China, while ssp. strangulata has a narrower distribution occurring only in two disjoined regions, southeastern Caspian Iran and Transcaucasia. A collection of 56 Ae. tauschii accessions was screened at adult stage against a mixture of pathotypes of stripe rust prevalent in the current wheat production in China. The results for three crop seasons indicated that among the 38 ssp. tauschii accessions, 37 were susceptible and only one was resistant, while all the 18 ssp. strangulata accessions were resistant. These results indicated that stripe rust resistance was related to taxonomic origin. Further genetic analysis revealed the resistance of stripe rust in ssp. strangulata accession AS2388 was conferred by a single dominant gene.     

Molecular characterization of two novel Glu-D1-encoded subunits from Chinese wheat (Triticum aestivum L.) landrace and functional properties of flours possessing the two novel subunits

The high molecular weight glutenin subunits (HMW-GS) can be used for wheat quality improvement. Two novel alleles (designated 1Dx1.5* and 1Dy12.2*, respectively) at the Glu-D1 locus were identified in the Chinese wheat landrace variety ‘Jiuquanjinbaoyin’ by comparison of subunit mobility with that previously identified in several standard hexaploid wheats. The 1Dx1.5* and 1Dy12.2* genes were isolated using the allele-specific PCR primers and the complete open reading frames (ORFs) were obtained. Allele 1Dx1.5* consists of 2487 bp encoding a mature protein of 827 amino acid residues, whereas 1Dy12.2* consists 1980 bp encoding 658 residues. Comparisons of amino acid sequences analysis showed that 1Dx1.5* had higher similarity with the HMW-GS isolated from the wheat related species (Aegilops tauchi Coss.) than from the bread wheat varieties (Triticum aestivum L.). The 1Dy12.2* amino acid sequence showed a generally similar to the 1Dy12* isolated from Chinese endemic wheats. Meanwhile, the dough properties of the lines expressing (null, 7+8, 1.5*+10), (null, 7+8, 2+12.2*) and (null, 7+8, 2+12), respectively, were measured by a Mixograph, which demonstrates that the alleles 1.5*+10 can be considered as having positive impact on dough strength when compared with the alleles 2+12. In addition, the subunits 2+12.2* also showed a greater impact on dough strength than 2+12.     

Geographic patterns of Got1, Got2, Got3 and Est2 enzyme-encoding genes allelic variation in Aegilops tauschii Coss.

Geographic patterns of Got1, Got2, Got3 and Est2 enzyme-encoding genes allelic variation were investigated among 322 accessions of Aegilops tauschii Coss., 161 accessions of ssp. tauschii and 161 accessions of ssp. strangulata, representing all the species area. It was found that: (1) in the two ecologically different subspecies, ssp. tauschii and ssp. strangulata, the patterns of allelic variation of the four genes differ greatly; (2) the same allozymes have originated several times independently in different Ae. tauschii local populations; (3) allelic variation of Got1, Got3 and Est2 in ssp. strangulata corresponds to climatic conditions. The data obtained reflected that Ae. tauschii has been inhabiting its area from ancient times; and allelic variation patterns of Got1, Got2, Got3, Est2 loci were mostly formed by natural selection. Further investigations of these loci with molecular genetic methods are prospective for understanding the peculiarities of Ae. tauschii evolution.     

Chloroplast DNA non-coding sequences variation in Aegilops tauschii Coss.: evolutionary history of the species

Sequences of four chloroplast DNA non-coding regions, about 3,000?bp in total, were analysed in 112 Aegilops tauschii accessions, 56 of ssp. tauschii and 56 of ssp. strangulata, representing all of the species range. One inversion, 8 insertions/deletions, 18 base pair substitutions and 5 microsatellite loci were found. The data revealed that Ae. tauschii originated in Caucasia. Neither of the two Ae. tauschii subspecies was an ancestor to one another. Aegilops tauschii divided into ssp. tauschii and ssp. strangulata at the very beginning of its existence as a species. Subspecies tauschii was the first to start geographic expansion and relatively rapidly occupied a vast area from Caucasia—eastward up to central Tien Shan and western Himalayas. In contrast to ssp. tauschii, geographic spread of ssp. strangulata was a complicated, multi-stage and slow process. At the beginning of ssp. strangulata evolutionary history its major phylogenetic lineage for a lengthy time span had existed as a small isolated population. Several forms of ssp. strangulata, better adapted to relatively moister and cooler habitats, had originated. Each of these forms has gradually forced out ssp. tauschii from some part of its area in the west, up to central Kopet-Dag.     

Genetic diversity of the D-genome in <Emphasis Type="Italic">T. aestivum</Emphasis> and <Emphasis Type="Italic">Aegilops</Emphasis> species using SSR markers

Simple sequence repeats (SSRs), highly dispersed nucleotide sequences in genomes, were used for germplasm analysis and estimation of the genetic relationship of the D-genome among 52 accessions of T. aestivum (AABBDD), Ae. tauschii (D^tD^t), Ae. cylindrica (CCD^cD^c) and Ae. crassa (MMD^cr1D^cr1), collected from 13 different sites in Iran. A set of 21 microsatellite primers, from various locations on the seven D-genome chromosomes, revealed a high level of polymorphism. A total of 273 alleles were detected across all four species and the number of alleles per each microsatellite marker varied from 3 to 27. The highest genetic diversity occurred in Ae. tauschii followed by Ae. crassa, and the genetic distance was the smallest between Ae. tauschii and Ae. cylindrica. Data obtained in this study supports the view that genetic variability in the D-genome of hexaploid wheat is less than in Ae. tauschii. The highest number of unique alleles was observed within Ae. crassa accessions, indicating this species as a great potential source of novel genes for bread wheat improvement. Knowledge of genetic diversity in Aegilops species provides different levels of information which is important in the management of germplasm resources.     

Molecular cytogenetic identification of newly synthetic <Emphasis Type="Italic">Triticum kiharae</Emphasis> with high resistance to stripe rust

Six new amphiploids, Triticum kiharae Dorof. et Migusch. (2n?=?6x?=?42, A^tA^tGGDD), are described in this study. They were developed by the chromosome doubling of F₁ hybrid crosses between Triticum timopheevii Zhuk. (A^tA^tGG) with high resistance to stripe rust and Aegilops tauschii Cosson (DD) by colchicine treatment. These amphiploids showed a high level of fertility of 68–80% and exhibited relatively normal chromosome pairing in meiotic metaphase I. Individual chromosomes of T. kiharae could be identified by multicolor fluorescence in situ hybridization using the combination of oligonucleotides probes Oligo-pSc119.2-1, Oligo-pTa535-1, and Oligo-pTa71-2. T. kiharae exhibited high resistance to predominant stripe rust races CYR34, CYR31, CYR32, CYR33, and SY11-4 both during the seedling and adult stages. However, high molecular weight glutenin subunits from Ae. tauschii parents were only partially expressed in the T. kiharae background. These T. kiharae lines provide novel materials to widen the genetic diversity of the common wheat gene pool.     

Haplotype variations of gene Ppd-D1 in Aegilops tauschii and their implications on wheat origin

The Ppd-D1 controlling photoperiod response is an important gene for wheat adaptation since it affects heading time. In the present study, three haplotypes, i.e. haplotype I without deletion, haplotype II with a 24?bp deletion, and haplotype III with two deletions of 24 and 15?bp, were identified in the upstream of the coding region in 80 Ae. tauschii accessions. The haplotype distribution was related to subspecies taxon. All typical ssp. tauschii accessions had haplotype I, whereas all ssp. strangulata had haplotype III. The three haplotypes were observed in Ae. tauschii with morphologically intermediate forms between the two typical subspecies. Present results supported that ssp. strangulata or intermediate form was the D-genome donor of common wheat since only haplotype III were found in wheat. Moreover, a 16?bp deletion in exon 8 of gene Ppd-D1 exists in common wheat. However, none of Ae. tauschii accessions analyzed had the 16?bp deletion.     

Durum wheat cultivation associated with Aegilops tauschii in northern Iran

Hexaploid bread wheat (Triticum aestivum L. ssp. aestivum) is assumed to have originated by natural hybridization between cultivated tetraploid Triticum turgidum L. and wild diploid Aegilops tauschii Coss. This scenario is broadly accepted, but very little is known about the ecological aspects of bread wheat evolution. In this study, we examined whether T. turgidum cultivation still is associated with weedy Ae. tauschii in today’s Middle Eastern agroecosystems. We surveyed current distributions of T. turgidum and Ae. tauschii in northern Iran and searched for sites where these two species coexist. Ae. tauschii occurred widely in the study area, whereas cultivated T. turgidum had a narrow distribution range. Traditional durum wheat (T. turgidum ssp. durum (Desf.) Husn.) cultivation associated with weedy Ae. tauschii was observed in the Alamut and Deylaman-Barrehsar districts of the central Alborz Mountain region. The results of our field survey showed that the T. turgidum–Ae. tauschii association hypothesized in the theory of bread wheat evolution still exists in the area where bread wheat probably evolved.     

Spatial patterns of adenylate kinase,catalase, endopeptidase and fructose-1,6-diphosphatase encoding genes allelic variation in <Emphasis Type="Italic">Aegilops tauschii</Emphasis> Coss.

Investigation of spatial patterns of adenylate kinase, catalase, endopeptidase and fructose-1,6-diphosphatase encoding genes (Ak, Cat1, Cat2, Ep, Fdp) allelic variation in Aegilops tauschii was carried out. About 300 accessions, representing all the species range were taken for the study. Cat2 and Fdp loci are completely monomorphic in ssp. strangulata and in the western part of ssp. tauschii range, as well. Both Cat2 and Fdp are highly polymorphic in the eastern part of ssp. tauschii range, with the patterns of this polymorphism being discordant in these two loci. Ak ¹⁰⁸, a rare allele with sporadical spatial occurrence, was found in ssp. tauschii only. On the contrary, Ak ⁹² is absent in ssp. tauschii: it is the most common Ak allele in ssp. strangulata in Precaspian Iran, the most moist part of the area, and is very rare in other parts of ssp. strangulata area. Ep is a highly polymorphic locus with the highest level of variation in the west of Ae. tauschii area, where this species had originated. Ep allele variation patterns are rather similar in ssp. tauschii and ssp. strangulata. The data reveal the adaptive nature of Ak, Cat2, and Fdp allele variation, while Ep polymorphism seems to be mostly neutral.     

Distribution and diversity of Aegilops tauschii in Iran

The wide morphological variation of Aegilops tauschii has led to the distinction of different subspecies; a typical ssp. tauschii and a second ssp. strangulata. However some researchers pointed out the existance of the intermediate form among morphologically distinguished subspecies. Distribution, diversity and the relationship between different subspecies and the intermediate form were evaluated in the Iranian Ae. tauschii collection. This collection was classified to 15 different populations according to morphological similarities and the collecting origin of accessions. The highest variation was found in tauschii population of Golestan followed by tauschii populations of Gilan and Ardebill, whereas the lowest variation was observed in tauschii populations of central Iran. Two discriminant functions suggested that the length of rachis node and spikelet glume, particularly, the length/width ratios of these traits had the highest impact on identification of different forms. Mahalanobis distances (D ² ) between the two subspecies along with intermediate form on the multidimensional scaling plot showed that the intermediate form is more similar to ssp. tauschii than ssp. strangulata. Although, the diversity within the ssp. strangulata was not very high, it widely affected the diversity of Iranian accessions of Ae. tauschii through continues crossing with the more diversed subspecies, tauschii, during thousands of years. This fact had lead to expansion of its distribution from its origin to Northern Khorasan, Northern Semnan and Eastern Ardebill by producing the intermediate form.     

Allelic diversity of high molecular weight glutenin subunits (HMW-GS) in Iranian Aegilops tauschii Coss. accessions by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE)

Variation of high molecular weight glutenin subunits (HMW-GS) in 28 Iranian Aegilops tauschii (2n = 2x = 14, DD) accessions studied by sodium dodecyl sulphate electrophoresis method (SDS-PAGE). The results showed high variation of HMW-GS in the accessions. The range of frequency in 14 HMW-GS combinations was 3.57–25 % in the accessions. AMOVA showed the molecular variance between the geographic areas was lower than within the geographic areas. According to Nei’s genetic diversity, the highest diversity levels were in Semnan, Golestan and Azarbayjan, on the other hand the lowest levels of diversity were found in Khorasan, Gilan and Mazandaran accessions. Hence, the Caspian Sea South East accessions also Azerbayjan in Iran have more diversity. AMOVA did not show variance between strangulata and tauschii but there was more genetic diversity in ssp. tauschii subspecies in comparison of ssp. strangulata according to Nei’s gene diversity and Shannon information index. It showed Iranian Ae. tauschii have a good potential for bread making quality improvement in bread wheat.     

Powdery mildew resistance in Aegilops tauschii coss. and synthetic hexaploid wheats

Summary A collection of 400 Ae. tauschii (syn. Ae. squarrosa) Coss. accessions were screened for powdery mildew resistance based on the response patterns of 13 wheat cultivars/lines possessing major resistance genes to nine differential mildew isolates. 106 accessions showed complete resistance to all isolates, and 174 accessions revealed isolate-specific resistance, among which were 40 accessions exhibiting an identical response pattern as wheat cultivar Ulka/^*8Cc which is known to possess resistance gene Pm2. Expression of both complete and isolate-specific resistance from Ae. tauschii was observed in some synthetic hexaploid wheats derived from four mildew susceptible T. durum Desf. parents, each crossed with five to 38 resistant diploid Ae. tauschii accessions. Synthetic amphiploids involving different combinations of T. durum and Ae. tauschii generally showed a decrease in resistance compared with that expressed by the Ae. tauschii parental lines.     

Molecular characterization and diversity of puroindoline b-2 variants in cultivated and wild diploid wheat

Cloning and phylogenetic analysis of puroindoline b-2 variants in common wheat (Triticum aestivum L.) and its relatives would advance the understanding of the genetic diversity and evolution of puroindoline b-2 gene in common wheat and its related species. In the present study, common wheat (AABBDD) and four related species, including T. urartu (A^uA^u), Aegilops speltoides (SS), Ae. tauschii (DD), and T. turgidum (AABB) were sampled for the presence of novel alleles at Pinb2v-A1, Pinb2v-B1/Pinb2v-S1 and Pinb2v-D1 loci corresponding to common wheat puroindoline b-2 variants. Nine new alleles were identified at these loci, designated Pinb2v-A1a through Pinb2v-A1c, Pinb2v-S1a through Pinb2v-S1e, and Pinb2v-D1a. Alignment of puroindoline variants or alleles from common wheat and its relatives indicated that all alleles in diploid wheats are attributed to single nucleotide substitution when compared with puroindoline b-2 variants in polyploids. Deduced amino acid sequences showed that all three alleles at Pinb2v-A1 locus and four alleles (Pinb2v-S1a, Pinb2v-S1b, Pinb2v-S1c and Pinb2v-S1e) at the Pinb2v-S1 locus could not be normally translated due to the presence of premature stop codons, whereas Pinb2v-D1a at the Pinb2v-D1 locus and Pinb2v-S1d at the Pinb2v-S1 locus could be normally translated, possibly suggesting that the puroindoline b-2 variant in Ae. tauschii was more highly conserved than those in T. urartu and Ae. speltoides. Meanwhile, puroindoline b-2 variant could be normally translated in all of the durum and common wheat cultivars surveyed. None of the puroindoline b-2 alleles previously identified in durum and common wheat were found in the diploid genome donors examined here, even though a greater diversity of alleles were found in diploid wheat compared to polyploid wheat. These results likely reflect the evolutionary history of tetraploid and hexaploid wheats, although it may be that puroindoline b-2 variant alleles have been selected for stability and functionality in common and durum wheat. This study provides a survey of puroindoline b-2 variants in common wheat and its relatives, and provides useful information for understanding the genetic diversity of puroindoline-like genes and their duplication events in wheat.     

Stem and leaf rust resistance in wild relatives of wheat with D genome (Aegilops spp.)

Resistance to stem rust and leaf rust in five D genome species of wheat viz., 267 accessions of Aegilops tauschii Coss., 39 of Ae. cylindrica Host, 17 of Ae. ventricosa Tausch, 4 of Ae. crassa Boiss. and 8 of Ae. juvenalis (Thell.) Eig were evaluated at adult plant stage. Two hundred and thirty nine (90 %) accessions of Ae. tauschii, 30 (77 %) of Ae. cylindrica, 16 (94 %) of Ae. ventricosa, 3 (75 %) of Ae. crassa Boiss. and 5 (62.5 %) of Ae. juvenalis were resistant to stem rust pathotypes prevalent in South India at Wellington under field condition. Invariably, all the accessions of the five species were resistant to leaf rust pathotypes. Quantitative measurement of disease using area under the disease progress curve revealed the slow progress of disease in the resistant accessions compared to susceptible check (Agra Local). Since all the five species have D genome, it could be concluded that the genes present in D genome might play a vital role in leaf rust resistance, but in case of stem rust resistance wide range of differential response was noticed. Among the species evaluated, Ae. tauschii was exploited to a larger extent, followed by Ae. ventricosa and Ae. cylindrica for leaf and stem rust resistance because of the homology of D genome with hexaploid bread wheat. While, Ae. crassa and Ae. juvenalis could not be utilized so far, possibly due to partial homology which makes the transfer of traits difficult. So, these species have considerable potential as a source of rust resistance and may enhance the existing gene pool of resistance to stem and leaf rusts.     

Allelic variation and distribution of HMW glutenin subunit 1Ay in Triticum species

The allelic variation and distribution of high-molecular-weight (HMW) glutenin subunit 1Ay in 814 Triticum lines were investigated by sodium dodecyl sulfate polyacrylamide-gel electrophoresis (SDS–PAGE). 1Ay subunit existed in 13 out of analyzed 21 species. The four species T. turgidum L., T. polonicum L., T. turanicum Jakubz. and T. zhukovskyi Men. et Er. were firstly discovered with expressed 1Ay subunit. The distribution frequencies for diploid, tetraploid and hexaploid wheats were at 87.89, 20.31 and 1.79%, respectively. Among the observed eight 1Ay alleles, three with the electrophoretic mobilities similar to 1Bx6, 1By8, and between 1By8 and 1Dy10 were firstly observed. Five had the mobilities similar to 1Bx6, 1Bx7, 1By8, 1Dy10, and 1Dy12 in Glu-1B and Glu-1D loci of hexaploid wheat. It is very difficult to distinguish these 1Ay alleles in Glu-1Ay from those in hexaploid wheat. The predominant 1Ay alleles were those with the mobilities similar to 1Bx7, 1By8, 1Dy10 and 1Dy12, and faster than 1Dy12. Comparison results of 1Ay alleles in different species indicated that multiple diploid lines were involved in the evolution process of tetraploid wheat. The 1Ay allelic variations and genetic resources might be useful in the quality improvement of common wheat.     

Evaluation for resistance to Pyrenophora tritici-repentis in Aegilops tauschii Coss. and synthetic hexaploid wheat amphiploids

Summary A total of 59 diploid Aegilops tauschii Coss. (syn. Aegilops sguarrosa auct. non L.) and 39 synthetic hexaploid wheat accessions were evaluated for reaction to Pyrenophora tritici-repentis (Died.) Drechs. in a controlled environment, and classified using a disease rating system based on lesion type. 27 Ae. tauschii and 20 synthetic wheats were found to be resistant to tan spot disease. The overall mean disease ratings of Ae. tauschii and the synthetic wheat lines scored on a scale of 1 (resistant) to 5 (susceptible) were 1.80 and 2.38, respectively. Synthetic wheats generally showed a decrease in resistance, although several lines of synthetic wheat expressed a higher resistance than the diploid parents. Five synthetic wheat lines exhibited higher resistance than the standard resistant common wheat cultivar Red Chief.     

Aegilops tauschii: Genetic Variation in Iran

All the 79 Aegilops tauschii Coss. accessions of Iranian origin from Prof. Kihara’s collection were analyzed electrophoretically. Of 23 enzyme-encoding loci studied, 11 were polymorphic. In Iran Ae. tauschii is presented by ssp. tauschii and ssp. strangulata which distinctly differ genetically, morphologically and ecologically. Variation patterns of low polymorphic locus Aco2 and highly polymorphic Ep are similar in both subspecies. In contrast, variation of Acph1, Ak, Est2, Est5, Got1, Got2, Got3 and Lap is a set of diverse patterns which markedly differ between subspecies and natural regions also, implying that natural selection is involved.     

Molecular diversity of restriction enzyme sites, Indels and upstream open reading frames (uORFs) of 5′ untransalted regions (UTRs) of Waxy genes in Triticum L. and Aegilops L. species

5′ Untransalted regions (UTR) sequences of Waxy genes were amplified from all 81 Triticum L. and Aegilops L. species by PCR with specific primers. It was found that the sequence length at 7D loci was longer than that 7B and 7A. These sequences contained 170 singleton variable sites and 484 polymorphic sites and that the average length of Indels was 8.5?bp. There were abundant regions of restriction enzyme sites and two regions of simple sequence repeat, “GAA” and “CTGA”, in all sequences. A total of 65 uORFs were detected and classed into 37 types, with the variation in uORFs mainly due to single nucleotide polymorphisms (SNPs), and also to the presence of Indels. All sequences in tetraploids and hexaploids could be grouped into Types A, B, I, II, GI and GII based on sequence variation. Restriction enzyme sites, Indel polymorphisms and the classes of uORFs present together indicated that Type I was more similar to Ae. tauschii whereas Type II was more similar to Type B, and both more similar to Ae. longissima; Type A was more similar to Ae. speltoides. Population analysis was performed and Neighbour-joining trees derived from different species, types and accessions further confirmed that the ancestors of T. urartu, Ae. speltoides, Ae. longissima and Ae. tauschii were involved to the evolution of common wheat, and also implied that Ae. longissima might have participated later than Ae. speltoides. 5′ UTRs of Waxy genes in tetraploid and hexaploid species conserved characters from their respective progenitors when compared with diploid. For the first time, we are able to conclude there is abundant variation in SNPs, Indels and uORFs between 5′ UTRs of Waxy genes from different species related to common wheat, and suggest that further research could help to understand Waxy gene function more deeply and hence improve wheat breeding. Our results also show that three hexaploid species in China have unique diversity in the 5′ UTR of their Waxy gene.     

Relationship Between the Qualitative and Quantitative Compositions of Gluten Protein Types and Technological Properties of Synthetic Hexaploid Wheat Derived from Triticum durum and Aegilops tauschii

The contribution of the diploid wheat species Aegilops tauschii (Coss.) Schmall to the technological properties of bread wheat (Triticum aestivum L.) was previously studied by the investigation of synthetic hexaploids derived from tetraploid durum wheat (T. turgidum L.) and three diploid Ae. tauschii lines. The results indicated that bread volume, gluten index, SDS‐sedimentation volume, and maximum resistance of gluten were significantly influenced by the Ae. tauschii lines. To determine the relationship between technological properties and qualitative and quantitative compositions of gluten proteins, the flours of parental and synthetic lines were extracted using a modified Osborne fractionation. Gliadin and glutenin fractions were then characterized by reversed‐phase (RP) HPLC on C₈ silica gel. The HPLC patterns revealed typical differences between synthetic and parental lines. The gliadin patterns of three synthetic lines and the glutenin patterns of two synthetic lines were more similar to that of the diploid Ae. tauschii parents involved in the hybrids. In the glutenin pattern of one synthetic line, characteristics from both Ae. tauschii and the durum wheat parents were observed. The amount of total gliadin and gliadin types of the synthetic lines was mostly intermediate between those of the durum and Ae. tauschii parents. The amounts of total glutenin and glutenin types (HMW and LMW subunits) of the synthetic lines were generally higher than those of the parental lines, and the ratio of gliadins to glutenins was significantly decreased. High positive correlations were found between the amount of total glutenins, HMW, and LMW subunits and bread volume, maximum resistance and extension area of gluten, and SDS‐sedimentation volume. The ratio of gliadins to glutenin subunits had a strong negative influence on these properties. The protein content of the flours and the amount of total gluten proteins were not correlated with any of the technological properties. Results on the relationship between biochemical characteristics and the breadmaking properties indicated that wheat prebreeding would benefit from studies on protein types and quantification in the choice of parents. In addition, the potential of the diploid Ae. tauschii for improvement of breadmaking quality should be further exploited.     

Cloning and phylogenetic analysis of polyphenol oxidase genes in common wheat and related species

Cloning and phylogenetic analysis of polyphenol oxidase (PPO) genes in common wheat and its relatives would greatly advance the understanding of molecular mechanisms of grain PPO activity. In the present study, six wheat relative species, including T. urartu, T. boeoticum, T. monococcum, T. dicoccoides, T. durum and Ae. tauschii, were sampled to isolate new alleles at Ppo-A1 and Ppo-D1 loci corresponding to common wheat PPO genes, and seven new alleles were identified from these species, which were designated as Ppo-A1c (from T. urartu), Ppo-A1d (T. boeoticum), Ppo-A1e (T. monococcum and T. durum), Ppo-A1f (T. dicoccoides), Ppo-A1g (T. durum), Ppo-D1c (Ae. tauschii) and Ppo-D1d (Ae. tauschii), respectively. Five out of the seven alleles detected in the wheat relatives contained an open reading frame (ORF) of 1,731 bp, encoding a polypeptide of 577 residues, which is the same as those of Ppo-A1 and Ppo-D1 genes in common wheat, whereas, the full-length ORF of the allele Ppo-A1g from T. durum was not obtained, and a 73-bp deletion occurred in the third exon of Ppo-D1d, an allele from Ae. tauschii, resulting in a shorter polypeptide of 466 amino acids. The 191-bp insertion in the first intron reported previously in common wheat was also found in T. dicoccoides lines, implying that more than one tetraploid wheat lines may be involved in the origination of common wheat. Phylogenetic trees were constructed using the genomic DNA sequences of the seven alleles, together with four from common wheat and four partial PPO gene sequences deposited in GenBank. The genome tribe A was divided into two clusters, one of which contained Ppo-A1d and Ppo-A1e, and the other included the remaining five alleles at Ppo-A1 locus. The alleles from different clusters showed high sequence divergences, indicated by dozens of SNPs and five to six InDels. The genome tribe D comprised the alleles Ppo-D1a, Ppo-D1c, Ppo-D1d and Ppo-D1b, and the former three were clustered together, showing significant sequence divergence from Ppo-D1b. In addition, the relationships between these allelic variants and grain PPO activities were also discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.