Comparative RFLP mapping of the chlorotoluron resistance gene (Su1) in cultivated wheat (Triticum aestivum) and wild wheat (Triticum dicoccoides)

Chlorotoluron is a selective phenylurea herbicide widely used for broad-leaved and annual grass weed control in cereals. Variation in the response to chlorotoluron (CT) was found in both hexaploid bread wheat (Triticum aestivum L.) and wild tetraploid wheat (Triticum dicoccoides KöRN.). Here, we describe the comparative mapping of the CT resistance gene (Su1) on chromosome 6B in bread and wild wheat using RFLP markers. In bread wheat, mapping was based on 58 F₄ single-seed descent (SSD) plants of the cross between a genotype sensitive to chlorotoluron, ‘Chinese Spring’ (CS), and a resistant derivative, the single chromosome substitution line, CS (‘Cappele-Desprez’ 6B) [CS (CAP6B). In T dicoccoides, mapping was based on 37 F₂ plants obtained from the cross between the CT-susceptible accession B-7 and the resistant accession B-35. Nine RFLP probes spanning the centromere were chosen for mapping. In bread wheat Su1 was found to be linked to α-Amy-1 (9.84 cM) and Xpsr371 (5.2 cM), both on the long arm of 6B, and Nor2 (2.74 cM) on the short arm. In wild wheat the most probable linkage map was Nor2-Xpsr312-Su1-Pgk2, and the genetic distances between the genes were 24.8cM, 5.3cM, and 6.8cM, respectively. These results along with other published map data indicate that the linear order of the genes is similar to that found in T. aestivum. The results of this study also show that the Su1 gene for differential response to chlorotoluron has evolved prior to the domestication of cultivated wheat and not in response to the development and use of chemicals.     

High molecular weight glutenin subunit in durum wheat (T. durum)

Summary The diversity of high molecular weight (HMW) glutenin subunits of 502 varieties of durum wheat (Triticum durum) from 23 countries was studied using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Twenty-nine types of patterns were observed with 18 mobility bands. A total of 18 alleles were identified by comparing the mobilities of their subunits to those previously found in hexaploid wheat (T. aestivum) and in Triticum turgidum var. dicoccum. Five new alleles were detected: two on the Glu A1 and three on the Glu B1 locus. Comparison of the frequency of alleles in the three species T. aestivum, T. dicoccum and T. durum was investigated. Significant differences exist between each of these species on the basis of the frequency distributions of their three and four common alleles at the Glu A1 and Glu B1 locus, respectively. The Glu B1c allele occuring very frequently in hexaploid wheats was not found in the two tetraploid species. More than 83% of the T. durum analysed were found to have the Glu A1c (null) allele.     

Assessment of genomic and species relationships in Triticum and Aegilops by PAGE and by differential staining of seed albumins and globulins

Summary Endosperm protein components from common bread wheats (Triticum aestivum L.) and related species were extracted with aluminum lactate, pH 3.2, and examined by electrophoresis in the same buffer. Electrophoretic patterns of the albumins and globulins were compared to evaluate the possibility that a particular species might have contributed its genome to tetraploid or hexaploid wheat. Together with protein component mobilities, differential band staining with Coomassie Brilliant Blue R250 was employed to test the identity or non-identity of bands. Eight species and 63 accessions, representative of Triticum and Aegilops were tested. Considerable intraspecific variation was observed for patterns of diploid but not for tetraploid or hexaploid species. Patterns of some accessions of Triticum urartu agreed closely with major parts of the patterns of Triticum dicoccoides and T. aestivum. A fast-moving, green band was found in all accessions of T. urartu and of Triticum boeoticum, however, that was not found in those of T. dicoccoides or T. aestivum. This band was present in all accessions of Triticum araraticum and Triticum zhukovskyi. Patterns of Aegilops longissima, which has been suggested as the donor of the B genome, differed substantially from those of T. dicoccoides and T. aestivum. Finally, two marker proteins of intermediate mobility were also observed and may be used to discriminate between accessions of T. araraticum/T. zhukovskyi and those of T. dicoccoides/T. aestivum.     

HMW and LMW glutenin alleles among putative tetraploid and hexaploid European spelt wheat (<Emphasis Type="Italic">Triticum spelta</Emphasis> L.) progenitors

The allelic compositions of high- and low-molecular-weight subunits of glutenins (HMW-GS and LMW-GS) among European spelt (Triticum spelta L.) and related hexaploid and tetraploid Triticum species were investigated by one- and two-dimensional polyacrylamide-gel electrophoresis (PAGE) and capillary electrophoresis (CE). A total of seven novel glutenin alleles (designated A1a*, B1d*, B1g*, B1f*, B1j*, D1a* at Glu-1 and A3h at the Glu-3 loci, respectively) in European spelt wheat were detected by SDS-PAGE, which were confirmed further by employing A-PAGE and CE methods. Particularly, two HMW-GS alleles, Glu-B1d* coding the subunits 6.1 and 22.1, and Glu-B1f* coding the subunits 13 and 22*, were found to occur in European spelt with frequencies of 32.34% and 5.11%, respectively. These two alleles were present in cultivated emmer (Triticum dicoccum), but they were not observed in bread wheat (Triticum aestivum L.). The allele Glu-B1g* coding for 13* and 19* subunits found in spelt wheat was also detected in club wheat (Triticum compactum L.). Additionally, two alleles coding for LMW-GS, Glu-A3h and Glu-B3d, occurred with high frequencies in spelt, club and cultivated emmer wheat, whereas these were not found or present with very low frequencies in bread wheat. Our results strongly support the secondary origin hypothesis, namely European spelt wheat originated from hybridization between cultivated emmer and club wheat. This is also confirmed experimentally by the artificial synthesis of spelt through crossing between old European emmer wheat, T. dicoccum and club wheat, T. compactum.Communicated by H.F. Linskens     

Inheritance of B subunits of glutenin and ω-and γ-gliadins in tetraploid wheats

A double-1RS wheat-rye translocation line lacking all B subunits of glutenin was produced in durum wheat cv ‘Langdon’ for use in backcrosses and testcrosses in the study of the inheritance of low-molecular-weight (LMW) glutenin subunits in tetraploid wheats. The B subunits of glutenin and γ-and ω-gliadin bands present in parents derived from Triticum durum and T. dicoccoides, encoded by Glu-3 and Gli-1 loci, respectively, were found to be inherited mainly as units (blocks), as reported previously. Two rare recombination events between the Glu-A3 and Gli-A1 loci were detected in testcross progeny from ‘Edmore’ x T. dicoccoides landrace 19–27. Several rare recombinants were also detected within the 1BS-controlled B subunits of glutenin blocks, suggesting that there are two separate tightly linked loci (3.07±1.35 cM) within the Glu-B3 ‘locus’. Evidence was also obtained for the presence of an additional locus coding for a B subunit of glutenin in ‘Edmore’ that is loosely linked (20.9±3.18%) with the main Glu-B3 ‘locus’.     

N-banded karyotypes of wheat species

Nine of the twenty-one chromosome pairs of the hexaploid wheat Triticum aestivum var. Chinese Spring (genome constitution AABBDD) show distinctive N-banding patterns. These nine chromosomes are 4A, 7A and all of the B genome chromosomes. The remaining chromosomes show either faint bands or no bands at all. Tetraploid wheat, T. dicoccoides (AABB), showed banded chromosomes similar to those observed in the hexaploid. Of the diploid species T. monococcum, T. boeoticum, T. urartu and Aegilops sauarrosa showed little or no banding as would be expected of donors of the A and D genomes. Ae. speltoides had a number of N-banded chromosomes as would be expected of a candidate for the B genome donor. Since N-bands are not evident on some nucleolar organiser chromosomes, the staining specificity cannot be correlated with the presence of nucleolar organiser regions.     

Study on the response of diploid,tetraploid and hexaploid species of wheat to the elevated CO2

Study was done to compare the response of Triticum aestivum (hexaploid), Triticum durum (tetraploid) and Triticum monococcum (diploid) wheat species to the elevated CO₂ using Free Air CO₂ Enrichment (FACE) facility. It was demonstrated that the modern cultivar of wheat Triticum aestivum (hexaploid) was largely sink limited. It appeared to have less photosynthesis per unit leaf area than Triticum monococcum (diploid wheat). While leaf size, grain weight and amylase activity increased with the ploidy level from diploid to hexaploid wheat forms, the photosynthetic rate was reduced significantly. These wheat species responded differentially to the elevated CO₂. The larger leaf area and greater seed weight and presence of 38 KDa protein band caused by elevated CO₂ had additive effect in improving the productivity of hexaploid wheat by changing the source sink ratio. Whereas, such a source sink balance was not induced by elevated CO₂ in diploid wheat. The increasing CO₂ may present opportunities to breeders and possibly allow them to select for cultivars responsive to the elevated CO₂ with better sink potential.Key words: Elevated CO₂, FACE technology, Photosynthesis, Seed weight, Source sink ratio, Triticum     

Confirmation of primitive chromosome structure in the hexaploid wheats

Summary Hybrids between Triticum aestivum cv Chinese Spring (CS) and T. dicoccoides of chromosome type E_1a showed only a few or no trivalents at meiosis, but both trivalents and quadrivalents were shown by hybrids with six other types. Since there is strong evidence that the E_1a type has the primitive chromosome structure of T. dicoccoides, Chinese Spring can be said to have the primitive chromosome structure of the hexaploid wheats in regard to reciprocal translocation.Contribution no. 51 from the Plant Germ-plasm Institute, Faculty of Agriculture, Kyoto University, Kyoto, Japan     

Transferability of wheat microsatellites to diploid Triticeae species carrying the A, B and D genomes

Hexaploid wheat (Triticum aestivum L em Thell) is derived from a complex hybridization procedure involving three diploid species carrying the A, B and D genomes. In this study, we evaluated the ability of microsatellite sequences from T. aestivum to be revealed on different ancestral diploid species more or less closely related, i.e. to test for their transferability. Fifty five primer pairs, evenly distributed all over the genome, were investigated. Forty three of them mapped to single loci on the hexaploid wheat genetic map although only 20 (46%) gave single PCR products; the 23 others (54%) gave more than one band with either only one being polymorphic, the others remaining monomorphic, or with several co-segregating polymorphic bands. The other 12 detected two (9) or three (3) different loci. From the 20 primer pairs which gave one amplification pro- duct on hexaploid wheat, nine (45%) also amplified products on only one of the diploid species, and seven (35%) on more than one. Four microsatellites (20%) which mapped to chromosomes from the B genome of wheat, did not give any amplification signal on any of the diploid species. This suggests that some regions of the B genome have evolved more rapidly compared to the A or D genomes since the emergence of polyploidy, or else that the donor(s) of this B genome has(have) not yet been identified. Our results confirm that Triticum monococcum ssp. urartu and Triticum tauschii were the main donors of the A and D genomes respectively, and that Aegilops speltoides is related to the ancestor(s) of the wheat polyploid B genome. Received: 21 June 2000 / Accepted: 15 November 2000     

Map-based analysis of the tenacious glume gene Tg-B1 of wild emmer and its role in wheat domestication

The domestication of wheat was instrumental in spawning the civilization of humankind, and it occurred through genetic mutations that gave rise to types with non-fragile rachises, soft glumes, and free-threshing seed. Wild emmer (Triticum turgidum ssp. dicoccoides), the tetraploid AB-genome progenitor of domesticated wheat has genes that confer tenacious glumes (Tg) that underwent genetic mutations to give rise to free-threshing wheat. Here, we evaluated disomic substitution lines involving chromosomes 2A and 2B of wild emmer accessions substituted for homologous chromosomes in tetraploid and hexaploid backgrounds. The results suggested that both chromosomes 2A and 2B of wild emmer possess genes that inhibit threshability. A population of recombinant inbred lines derived from the tetraploid durum wheat variety Langdon crossed with a Langdon — T. turgidum ssp. dicoccoides accession PI 481521 chromosome 2B disomic substitution line was used to develop a genetic linkage map of 2B, evaluate the genetics of threshability, and map the gene derived from PI 481521 that inhibited threshability. A 2BS linkage map comprised of 58 markers was developed, and markers delineated the gene to a 2.3 cM interval. Comparative analysis with maps containing the tenacious glume gene Tg-D1 on chromosome arm 2DS from Aegilops tauschii, the D genome progenitor of hexaploid wheat, revealed that the gene inhibiting threshability in wild emmer was homoeologous to Tg-D1 and therefore designated Tg-B1. Comparative analysis with rice and Brachypodium distachyon indicated a high level of divergence and poorly conserved colinearity, particularly near the Tg-B1 locus. These results provide a foundation for further studies involving Tg-B1, which, together with Tg-D1, had profound influences on wheat domestication.     

Structural evolution of wheat chromosomes 4A, 5A,and 7B and its impact on recombination

The construction of comparative genetic maps of chromosomes 4A^m and 5A^m of Triticum monococcum and chromosomes of homoeologous groups 4, 5 and 7 of T. aestivum has provided insight into the evolution of these chromosomes. The structures of chromosomes 4A, 5A and 7B of modern-day hexaploid bread wheat can be explained by a 4AL/5AL translocation that occurred at the diploid level and is present both in T. monococcum and T. aestivum. Three further rearrangements, a 4AL/7BS translocation, a pericentric inversion and a paracentric inversion, have taken place in the tetraploid progenitor of hexaploid wheat. These structural rearrangements and the evolution of chromosomes 4A, 5A and 7B of bread wheat are discussed. The presence of the 4AL/5AL translocation in several Triticeae genomes raises two questions — which state is the more primitive, and is the translocation of mono- or poly-phylogenetic origin? The rearrangements that have occurred in chromosome 4A resulted in segments of both arms having different positions relative to the telomere, compared to 4A^m and to 4B and 4D. Comparisons of map length in these regions indicate that genetic length is a function of distance from the telomere, with the distal regions showing the highest recombination.     

Leaf dehydroascorbate reductase and catalase activity is associated with soil drought tolerance in bread wheat

A number of morphological, physiological and phenological traits have been suggested as significant markers of adaptation to drought in bread wheat (Triticum aestivum L.). This study was aimed at the identification of a relationship between dehydroascorbate reductase (DHAR, EC 1.8.5.1) and catalase (CAT, EC 1.11.1.6) activities in leaves of wheat plants and stability of yield components under water deficit. The single chromosome substitution lines of cv. Chinese Spring carrying separate chromosomes from the donor Synthetic 6x, an artificial hexaploid combining the genomes of the two wild species, Triticum dicoccoides (AABB) and Aegilops tauschii (DD), were the objects of the investigations. The activities of the DHAR and CAT were correlated with flag leaf relative water content and two indexes of stability of grain yield components under drought across the set substitution lines. The lines carrying a synthetic hexaploid homologous pair of chromosomes 1B, 1D, 2D, 3D or 4D all expressed a low constitutive level of DHAR and the lines carrying chromosomes 3B, 1D, 2D and 3D a low constitutive level of CAT. All were able to increase this level (by fourfold for DHAR and by 1.5-fold for CAT) in response to stress caused by water deficit. When challenged by drought stress, these lines tended to be the most effective in retaining the water status of the leaves and preventing the grain yield components from being compromised. The discovered genetic variability for enzymes activity in leaves of wheat might be a useful selection criterion for drought tolerance.     

Evidence for AEGILOPS SHARONENSIS Eig as the Donor of the B Genome of Wheat

A number of lines of evidence are advanced for the candidacy of Aegilops sharonensis Eig as the donor of the B genome of wheat. The cytoplasm of Ae. sharonensis is compatible with tetraploid wheat Triticum turgidum dicoccoides, as evidenced by the high level of chromosome pairing and fertility of the amphiploid Ae. sharonensis x T. turgidum dicoccoides. Ae. sharonensis chromosomes exhibit high levels of pairing with those of the B genome of wheat in hybrids with Ph-deficient hexaploid wheat and low levels of homoeologous pairing with T. monococcum chromosomes.——The amphidiploid between Ae. sharonensis and T. monococcum is very similar to T. turgidum dicoccoides in spike, spikelet and grain morphology. The karyotype of Ae. sharonensis resembles more closely that of extrapolated B genome karyotypes of wheat than do the karyotypes of other proposed B-genome donor species of Aegilops. Because of distinctiveness in cytological affinity and karyotype morphology between Ae. sharonensis and Ae. longissima, a separate genome symbol S^sh is proposed for the former species.     

Comparative characteristic of Triticum aestivum/Triticum durum and Triticum aestivum/Triticum dicoccum hybrid lines by genomic composition and resistance to fungal diseases under different environmental conditions

The genetic diversity of common wheat hybrid lines Triticum aestivum/Triticum durum and Triticum aestivum/Triticum dicoccum (2n = 42, F_6–7) using chromosome-specific microsatellite (SSR) markers and C-banding of chromosomes was studied. Cluster analysis of data obtained by 42 SSR markers indicated that the hybrid lines can be broken into three groups according to their origin. There were two cases of complete genetic similarity between lines 183₂-2/184₁-6 and 208-3/213-1, which were obtained using common wheat as the parental plants. In cross combinations, when the stabilization of the nuclear genome of hexaploid lines occurred against a background of the cytoplasmic genome of tetraploid wheats, there was a high level of divergence between sister lines, in some cases exceeding 50%. The evaluation of the degree of susceptibility of the lines to powdery mildew, leaf and stem rust, and septoria leaf blotch was performed under different environmental conditions. It was shown that resistance to powdery mildew and leaf rust significantly depended on the region where assays were conducted. An evaluation of the field data showed that the lines 195-3, 196-1, and 221-1 with T. durum genetic material displayed complex resistance to fungal pathogens in Western Siberia and the Republic of Belarus. For lines 195-3 and 196-1, one shows a possible contribution of chromosomes 4B and 5B in the formation of complex resistance to diseases. Hybrid lines with complex resistance can be used to expand the genetic diversity of modern common wheat cultivars for genes of immunity.     

Microsatellite tagging of the stripe-rust resistance gene YrH52 derived from wild emmer wheat, Triticum dicoccoides, and suggestive negative crossover interference on chromosome 1B

 Stripe rust caused by Puccinia striifomis West. is one of the most devastating diseases relating to wheat production. Wild emmer wheat, Triticum dicoccoides, the tetraploid progenitor of cultivated wheat, has proven to be a valuable source of novel stripe-rust resistance genes for wheat breeding. For example, T. dicoccoides accessions from Mt. Hermon, Israel, are uniformly and highly resistant to stripe-rust. The main objective of the present study is to map a stripe-rust resistance gene, derived from the unique Mt. Hermon population of wild emmer, using microsatellite markers. An F₂ mapping population was established by crossing stripe-rust resistant T. dicoccoides accession H52 from Mt. Hermon with the Triticum durum cultivar Langdon. The stripe-rust resistance derived from accession H52 was found to be controlled by a single dominant gene which was temporarily designated as YrH52. Out of 120 microsatellite markers tested, 109 (91%) showed polymorphism between the parental lines. Among 79 segregating microsatellite loci generated from 56 microsatellite primer pairs, nine were linked to YrH52 with recombination frequencies of 0.02–0.35, and LOD scores of 3.56–54.22. A genetic map of chromosome 1B, consisting of ten microsatellite loci and the stripe-rust resistance gene YrH52, was constructed with a total map length of 101.5 cM. YrH52 is also closely linked to RFLP marker Nor1 with a map distance of 1.4 cM and a LOD value of 29.62. Apparent negative crossover interference was observed in chromosome 1B, especially in the region spanning the centromere. Negative crossover interference may be a common characteristic of gene-rich regions or gene clusters in specific chromosomes. Received: 30 October 1998 / Accepted: 2 November 1998     

Allelic variation of high molecular weight glutenin subunits of bread wheat in Hebei province of China

In common wheat (Triticum aestivum L.), allelic variations of Glu-1 loci have important influences on grain end-use quality. The allelic variations in high molecular weight glutenin subunits (HMW-GSs) were identified in 151 hexaploid wheat varieties representing a historical trend in the cultivars introduced or released in Hebei province of China from the years 1970s to 2010s. Thirteen distinct alleles were detected for Glu-1. At Glu-A1, Glu-B1 and Glu-D1, we found that the most frequent alleles were the 1 (43.0%), 7+8 (64.9%), 2+12 (74.8%) alleles, respectively, in wheat varieties. Twenty two different HMW-GS compositions were observed in wheat. Twenty-five (16.6%) genotypes possessed the combination of subunits 1, 7+8, 2+12, 25 (16.6%) genotypes had subunit composition of 2*, 7+8, 2+12; 20 (13.2%) genotypes had subunit composition of null, 7+8, 2+12. The frequency of other subunit composition was less than 10%. The Glu-1 quality score greater than or equal to 9 accounted for 20.6% of the wheat varieties. The percentage of superior subunits (1 or 2* subunit at Glu-A1 locus; 7+8, 14+15 or 17+18 at Glu-B1 locus; 5+10 or 5+12 at Glu-D1 locus) was an upward trend over the last 40 years. The more different superior alleles correlated with good bread-making quality should be introduced for their usage in wheat improvement efforts.     

Genetic analysis of photosynthetic variation in hexaploid and tetraploid wheat and their interspecific hybrids

Intra- and inter-specific variation in CO₂ assimilation rate (A) in Triticum spp. is well documented for reproductive growth stages. Research was conducted to characterize early vegetative photosynthetic variation in a diverse set of cultivated hexaploid wheat (T. aestivum L.) germplasm and in wild tetraploid (T. dicoccoides Korn) and hexaploid x tetraploid populations. Choice of hexaploid genotypes was based on maximum genetic distance between cultivars within the HRW and SRW wheat classes of the USA. The tetraploid material was produced by hybridizing two accessions of T. dicoccoides previously shown to differ widely in A and A/Chl but with similar leaf morphology. Genetic variability in the HRW and SRW gene pools was attributed to more recently developed descendent lines and unrelated lines rather than parental lines. Phenotypic distributions for A, stomatal conductance (gs), and internal CO₂ concentration (Ci) in the F₂ tetraploid population were continuous and showed transgressive segregation, reflecting quantitative inheritance with intermediate heritability. Variability in A was not associated with chlorophyll content or CO₂ supply to the mesophyll measured as Ci. Genetic variability in A was also observed in the interspecific backcross population, 2*TAM W-101/PI 428109, thereby providing a germplasm pool to select for high A while restoring the D genome of hexaploid wheat. These results suggest that genetic improvement of vegetative assimilation rate is feasible in hexaploid wheat via homologous transfer from an alien source.Abbreviations HRW hard red winter - LA leaf area - r_G genotypic correlation - r_P phenotypic correlation - SRW soft red winter     

Photosynthetic response of tetraploid and hexaploid wheat to water stress

Photosynthetic characteristics of ear and flag leaves of wheat species, tetraploid Triticum dicoccoides Kom and hexaploid Bima1, were studied in plants grown under well-watered (WW) and water-stressed (WS) conditions. Compared to ears, flag leaves exhibited higher photosynthetic rate (P _N) at the filling stage, but more severe decrease under WS. P _N in the tetraploid wheat ear remained higher than that in the hexaploid wheat during the grain-filling stage. Water stress decreased PN in both the organs; this decline was caused by a reduction in Rubisco activity, not by drought-induced stomatal limitation. Tetraploid wheat ears exhibited higher relative water content and water-use efficiency than that of hexaploid wheat, under WS. The change in phosphoenolpyruvate carboxylase activity and carbon isotope composition indicated the absence of C₄ metabolism in the ears of both species under both conditions. The improved performance of the tetraploid wheat ears under WS was associated with better water relations.     

Allelic variations in <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci of historical and modern Iranian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Proline and glutamine-rich wheat seed endosperm proteins are collectively referred to as prolamins. They are comprised of HMW-GSs, LMW-GSs and gliadins. HMW-GSs are major determinants of gluten elasticity and LMW-GSs considerably affect dough extensibility and maximum dough resistance. The inheritance of glutenin subunits follows Mendelian genetics with multiple alleles in each locus. Identification of the banding patterns of glutenin subunits could be used as an estimate for screening high quality wheat germplasm. Here, by means of a two-step 1D-SDS-PAGE procedure, we identified the allelic variations in high and low-molecular-weight glutenin subunits in 65 hexaploid wheat (Triticum aestivum L.) cultivars representing a historical trend in the cultivars introduced or released in Iran from the years 1940 to 1990. Distinct alleles 17 and 19 were detected for Glu-1 and Glu-3 loci, respectively. The allelic frequencies at the Glu-1 loci demonstrated unimodal distributions. At Glu-A1, Glu-B1 and Glu-D1, we found that the most frequent alleles were the null, 7 + 8, 2 + 12 alleles, respectively, in Iranian wheat cultivars. In contrast, Glu-3 loci showed bimodal or trimodal distributions. At Glu-A3, themost frequent alleles were c and e. At Glu-B3 the most frequent alleles were a, b and c. At Glu-D3 locus, the alleles b and a, were the most and the second most frequent alleles in Iranian wheat cultivars. This led to a significantly higher Nei coefficient of genetic variations in Glu-3 loci (0.756) as compared to Glu-1 loci (0.547). At Glu-3 loci, we observed relatively high quality alleles in Glu-A3 and Glu-D3 loci and low quality alleles at Glu-B3 locus.     

Wheat's wild relatives vary in their response to nitrogen and ozone

The wild relatives of bread wheat ( Triticum aestivum ) are valued by plant breeders for their genetic diversity. However, increasing levels of nitrogen (N) deposition and ground‐level ozone (O₃) threaten plant biodiversity in the Mediterranean and Near‐East, a hotspot for many crop wild relatives. Knowledge of the effect of these air pollutants in combination is still limited, but early indications are that effects vary depending on the level of pollutants, and on the sensitivity of the species to N and O₃. This study examined the responses of four important wheat wild relatives ( Aegilops tauschii , Aegilops speltoides , Triticum dicoccoides and Triticum monococcum ) and one modern wheat cultivar ( T. aestivum ‘Cadenza’) to treatments of N (equivalent to 50 kg ha^?1 year^?1 ammonium nitrate) and O₃ (100 ppb for 21 days), alone and in combination. Measurements included root, shoot and seed biomass, and electrolyte ratios. The O₃ sensitivity of A. tauschii and T. aestivum ‘Cadenza’ were exacerbated by the addition of N, while A. speltoides was found to be nitrophilous, with N ameliorating the negative effect of O_3. Both T. aestivum ‘Cadenza’ and T. dicoccoides produced immature seed heads, with the cultivar's seed head biomass reduced in response to O₃ and N + O₃ while that of T. dicoccoides was largely unaffected. These data suggest that all four wild relatives are likely to be affected when N and O₃ air pollutants co‐occur, and there in situ populations may therefore be at risk. Equally, the results of this study can inform use of their beneficial traits by wheat breeders, and alert them to the inadvertent inclusion of N and O₃ sensitivity.