Grains from ear to ear: the morphology of spelt and free-threshing wheat from Roman Mursa (Osijek), Croatia

Cereals were a significant part of the Roman diet, yet knowledge about their cultivation, distribution and consumption in certain regions is particularly lacking. In Europe, studies generally suggest that from the Iron Age to the Roman period there was a reduction in barley cultivation, an increase in spelt over emmer, a preference for free-threshing wheat over glume wheats, as well as the increased cultivation of rye and oats. Up till now, there was little evidence on crop cultivation in Croatia, but the discovery of around 24,000 cereal grains from the oven of a 2nd-4th c. ad Roman villa in the modern town of Osijek provides important insights into diet and subsistence in the Roman province of Pannonia. Here, the dominance of free-threshing wheat, spelt and rye with only a relatively small amount of other cereals, chaff and weeds corresponds well with this pattern seen elsewhere in Europe. The relatively clean grain deposit suggests that this sample represents processed grain ready for final food preparation and consumption at the villa. The morphological variation and overlap seen between the carbonised spelt and free-threshing wheat grains, as well as the identification of ‘stunted’ cereal grains, is also discussed.

     

The genetic origin of spelt and related wheats

Summary The genetic theory ofMcFadden andSears regarding the origin of spelt and related wheats is defended. This theory postulates thatT. spelta arose fromT. dicoccum (orT. dicoccoides) x Ae. squarrosa in the natural area of the latter. This hybrid became a component of a mixed crop of emmer and einkorn, but only a fractional one, and this medley was brought to southwestern Germany and northern Switzerland, where conditions particularly favorable to spelt caused it to emerge as a major crop.

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Zusammenfassung Die genetische Theorie vonMcFadden undSears über den Ursprung des Spelzes und verwandter Weizen wird unterstützt. Nach dieser Theorie istT. spelta aus der KreuzungT. dicoccum (oderT. dicoccoides) x Ae. squarrosa im natürlichen Areal vonAe. squarrosa entstanden. Diese Hybride wurde ein, allerdings nur in Spuren vorhandener Bestandteil einer aus Emmer und Einkorn bestehenden Mischkultur, und dieses Gemisch gelangte nach Südwestdeutschland und der nördlichen Schweiz, wo für den Spelz besonders günstige Bedingungen zu seiner Entwicklung als selbständige Kulturpflanze führten.

     

The Q locus of Iranian and European spelt wheat

A dominant allele at the Q locus on chromosome 5A is believed to be the principal factor responsible for free-threshing, square-head spikes with a non-fragile rachis in bread wheat, Triticum aestivum ssp. aestivum. The spelt syndrome, resulting in pyramidal spikes with a brittle rachis and hulled grain in T. aestivum, is believed to be principally caused by the q allele. Chromosome 5A of European and Iranian spelt was substituted for 5A of bread wheat and the lines were characterized with molecular markers. The substitution of bread wheat chromosome 5A by 5A of European spelt resulted in weakly hulled, pyramidal spikes with a non-brittle rachis, whereas and the substitution of 5A by 5A of Iranian spelt did not alter spike morphology at all. It is concluded that the expression of the spelt syndrome depends, to a large extent, on the interactions of q with genes controlling glume tenacity and rachis fragility on other chromosomes. The genetic basis for the spelt syndrome and the apparent presence of the Q allele in Iranian spelt are discussed. Received: 14 April 1999 / Accepted: 21 July 1999     

Sequence divergence between spelt and common wheat

Key message

Sequence comparison between spelt and common wheat reveals that the former has huge potential in enriching the genetic variation of the latter.

Abstract

Genetic variation is the foundation of crop improvement. By comparing genome sequences of a Triticum spelta accession and one of its derived hexaploid lines with the sequences of the international reference genotype Chinese Spring, we detected variants more than tenfold higher than those present among common wheat (T. aestivum L) genotypes. Furthermore, different from the typical ‘V-shaped’ pattern of variant distribution often observed along wheat chromosomes, the sequence variation detected in this study was more evenly distributed along the 3B chromosome. This was also the case between T. spelta and the wild emmer genome. Genetic analysis showed that T. spelta and common wheat formed discrete groups. These results showed that, although it is believed that the spelt and common wheat are evolutionarily closely related and belong to the same species, a significant sequence divergence exists between them. Thus, the values of T. spelta in enriching the genetic variation of common wheat can be huge.

     

A genetic basis for the origin of six different isolectins in hexaploid wheat

Wheat (Triticum aestivum) germ agglutinin represents a complex mixture of multiple isolectin forms. Upon ion exchange chromatography at pH 3.8, three isolectins can be separated, each of which is composed of two identical subunits. At pH 5.0, however, three additional isolectins can be distinguished, which are built up of two different subunits (heteromeric lectins). Evidence is presented that these heterodimers are normal constituents of the wheat embryo cells. Analyses of the isolectin patterns in extracts from Triticum monococcum, Triticum turgidum dicoccum and Triticum aestivum, provide evidence that each genome, either in simple or complex (polyploid) genomes, directs the synthesis of a single lectin subunit species. In addition, a comparison of the isolectin pattern in these wheat species of increasing ploidy level, made it possible to determine unequivocally the genome by which the individual lectin subunits in polyploid species are coded for. The possible use of lectins in studies on the origin of individual genoms in polyploid species is discussed.Abbreviations CL cereal lectin - PBS phosphate buffered saline - SP Sephadex sulfopropyl Sephadex - WGA wheat germ agglutinin     

Waxy genes from spelt wheat: new alleles for modern wheat breeding and new phylogenetic inferences about the origin of this species

Background and Aims

Waxy proteins are responsible for amylose synthesis in wheat seeds, being encoded by three waxy genes (Wx-A1, Wx-B1 and Wx-D1) in hexaploid wheat. In addition to their role in starch quality, waxy loci have been used to study the phylogeny of wheat. The origin of European spelt (Triticum aestivum ssp. spelta) is not clear. This study compared waxy gene sequences of a Spanish spelt collection with their homologous genes in emmer (T. turgidum ssp. dicoccum), durum (T. turgidum ssp. durum) and common wheat (T. aestivum ssp. aestivum), together with other Asian and European spelt that could be used to determine the origin of European spelt.

Methods

waxy genes were amplified and sequenced. Geneious Pro software, DNAsp and MEGA5 were used for sequence, nucleotide diversity and phylogenetic analysis, respectively.

Key Results

Three, four and three new alleles were described for the Wx-A1, Wx-B1 and Wx-D1 loci, respectively. Spelt accessions were classified into two groups based on the variation in Wx-B1, which suggests that there were two different origins for the emmer wheat that has been found to be part of the spelt genetic make-up. One of these groups was only detected in Iberian material. No differences were found between the rest of the European spelt and the Asiatic spelt, which suggested that the Iberian material had a different origin from the other spelt sources.

Conclusions

The results suggested that the waxy gene variability present in wheat is undervalued. The evaluation of this variability has permitted the detection of ten new waxy alleles that could affect starch quality and thus could be used in modern wheat breeding. In addition, two different classes of Wx-B1 were detected that could be used for evaluating the phylogenetic relationships and the origins of different types of wheat.     

The genetic control of grain esterases in hexaploid wheat

Summary A comparison of EST-5 grain esterase phenotypes from wheat-alien amphiploid, addition and substitution genotypes, resolved by flat-bed isoelectric focusing identified homoeologous Est-5 loci on chromosome 3H of Hordeum vulgare, 3H^ch of H. chilense, 3S^b of Aegilops bicornis, 3S¹ of Ae. sharonensis and Ae. longissima and 6R of Secale cereale and 6R^m of S. montanum. The Est-5 genes in alien species provide evidence for chromosome homoeology with wheat.     

The genetic control of grain esterases in hexaploid wheat

Summary Analysis of grain esterase isozymes in Chinese Spring aneuploid genotypes by IEF confirmed that genes on the long arms of chromosomes 3A, 3B and 3D (Est-5) control the production of 19 isozymes. Allelic variants have been found for the isozyme pattern controlled by each chromosome. Segregational data involving null alleles and complex phenotypic differences indicate that the wheat grain esterases are encoded by three compound and probably homoeoallelic loci, each capable of producing at least six different isozymes. In a sample of 138 hexaploid genotypes, seven alleles were distinguished.     

The genetical control and tissue-specificity of esterase isozymes in hexaploid wheat

A comparative genetic analysis of esterase (E.C.3.1.1.1) isozymes of wheat cultivar Chinese Spring in endosperm, embryo, coleoptile, leaf and root tissues revealed eight sets of isozymes characterised by different tissue specificities, pI ranges and the chromosomal locations of their controlling genes. This data was considered together with previously published work, resulting in a proposed rationalization of nine sets of wheat esterase isozymes. Although this classification included two sets of isozymes controlled by genes on the short arms of homoeologous group 3 chromosomes and three sets on the long arms of the same chromosomes, for which no recombination evidence of genetic distinctness has been obtained among either group, it is argued that the different characteristics of the various sets warrant retention of separate set nomenclatures. Previously unreported esterase genes includeEst-9, a low pI, monomeric, embryo-specific group with controlling genes on chromosomes 3BS and 3DS and two further members ofEs-1,Est-H1 inHordeum vulgare andEst-S ^l1 inAegilops longissima.     

Genetic structure of Argentinean hexaploid wheat germplasm

The identification of genetically homogeneous groups of individuals is an ancient issue in population genetics and in the case of crops like wheat, it can be valuable information for breeding programs, genetic mapping and germplasm resources. In this work we determined the genetic structure of a set of 102 Argentinean bread wheat (Triticum aestivum L.) elite cultivars using 38 biochemical and molecular markers (functional, closely linked to genes and neutral ones) distributed throughout 18 wheat chromosomes. Genetic relationships among these lines were examined using model-based clustering methods. In the analysis three subpopulations were identified which correspond largely to the origin of the germplasm used by the main breeding programs in Argentina.     

The expression of salt tolerance from Triticum tauschii in hexaploid wheat

Summary Accessions of Triticum tauschii (Coss.) Schmal. (D genome donor to hexaploid wheat) vary in salt tolerance and in the rate that Na⁺ accumulates in leaves. The aim of this study was to determine whether these differences in salt tolerance and leaf Na⁺ concentration would be expressed in hexaploid wheat. Synthetic hexaploids were produced from five T. tauschii accessions varying in salt tolerance and two salt-sensitive T. turgidum cultivars. The degree of salt tolerance of the hexaploids was evaluated as the grain yield per plant in 150 mol m^-3 NaCl relative to grain yield in 1 mol m^-3 NaCl (control). Sodium concentration in leaf 5 was measured after the leaf was fully expanded. The salt tolerance of the genotypes correlated negatively with the concentration of Na⁺ in leaf 5. The salt tolerance of the synthetic hexaploids was greater than the tetraploid parents primarily due to the maintenance of kernel weight under saline conditions. Synthetic hexaploids varied in salt tolerance with the source of their D genome which demonstrates that genes for salt tolerance from the diploid are expressed at the hexaploid level.     

Synthetic hexaploid wheat and its utilization for wheat genetic improvement in China

Synthetic hexaploid wheat （Triticum turgidum x Aegilops tauschii） was created to explore for novel genes from T. turgidum and Ae. tauschii that can be used for common wheat improvement. In the present paper, research advances on the utilization of synthetic hexaploid wheat for wheat genetic improvement in China are reviewed. Over 200 synthetic hexaploid wheat （SHW） accessions from the International Maize and Wheat Improvement Centre （CIMMYT） were introduced into China since 1995. Four cultivars derived from these, Chuanmai 38, Chuanmai 42, Chuanmai 43 and Chuanmai 47, have been released in China. Of these, Chuanmai 42, with large kernels and resistance to stripe rust, had the highest average yield （〉 6 t/ha） among all cultivars over two years in Sichuan provincial yield trials, outyielding the commercial check cultivar Chuanmai 107 by 22,7%. Meanwhile, by either artificial chromosome doubling via colchicine treatment or spontaneous chromosome doubling via a union of unreduced gametes （2n） from T. turgidum-Ae, tauschii hybrids, new SHW lines were produced in China. Mitotic-like meiosis might be the cytological mechanism of spontaneous chromosome doubling. SHW lines with genes for spontaneous chromosome doubling may be useful for producing new SHW-alien amphidiploids and double haploid in wheat genetic improvement.     

The structure of the Aegilops tauschii genepool and the evolution of hexaploid wheat

 Polymorphism in the lengths of restriction fragments at 53 single-copy loci, the rRNA locus Nor3, and the high-molecular-weight glutenin locus Glu1 was investigated in the D genome of hexaploid Triticum aestivum and that of Aegilops tauschii, the source of the T. aestivum D genome. The distribution of genetic variation in Ae. tauschii suggests gene flow between Ae. tauschii ssp. strangulata and ssp. tauschii in Iran but less in Transcaucasia. The “strangulata” genepool is wider than it appears on the basis of morphology and includes ssp. strangulata in Transcaucasia and southeastern (SE) Caspian Iran and ssp. tauschii in north-central Iran and southwestern (SW) Caspian Iran. In the latter region, Ae. tauschii morphological varieties ‘meyeri’ and ‘typica’ are equidistant to ssp. strangulata in Transcaucasia, and both belong to the “strangulata” genepool. A model of the evolution of Ae. tauschii is presented. On the geographic region basis, the D genomes of all investigated forms of T. aestivum are most closely related to the “strangulata” genepool in Transcaucasia, Armenia in particular, and SW Caspian Iran. It is suggested that the principal area of the origin of T. aestivum is Armenia, but the SW coastal area of the Caspian Sea and a corridor between the two areas may have played a role as well. Little genetic differentiation was found among the D genomes of all investigated free-threshing and hulled forms of T. aestivum, and all appear to share a single D-genome genepool, in spite of the fact that several Ae. tauschii parents were involved in the evolution of T. aestivum. Received: 17 November 1997 / Accepted: 17 March 1998     

Genome inheritance in populations derived from hexaploid/tetraploid and tetraploid/hexaploid wheat crosses

Hexaploid/tetraploid and tetraploid/hexaploid wheat hybrids were established using the hexaploid (Triticum aestivum L.) bread wheat LRC2010-150 and the tetraploid durum wheat (T. turgidum spp. durum) WID802. Thirty F₂ progeny from each cross were characterised using Diversity Arrays Technology (DArTseq?) markers to determine whether there are differences between the crosses in the proportion of A, B and D genomic material inherited from each parent. Inheritance of the A and B genome from the tetraploid durum parent varied from 32 to 63% among the 60 lines assessed, and results indicated significant differences between the two F₂ populations in the mean overall proportion of chromosomes A and B inherited from each parent. Significant differences were also observed between the crosses in the proportion of chromosomal segments on 2B, 3A, 3B and 4A inherited from the tetraploid parent. The F₂ populations also showed significant differences in the average retention of D chromosomes per line with the tetraploid/hexaploid cross retaining a mean of 2.83 chromosomes while the reciprocal cross retained a mean of 1.8 chromosomes per line. A strong negative correlation was observed in individual lines from both populations between the proportion of the A and B genome inherited from the tetraploid durum parent and the retention of the D genome. The implication of these results for the design of efficient crossing strategies between hexaploid and tetraploid wheats is discussed.     

Comparative performance of bread wheat and hexaploid triticale cytoplasms

Summary Thirteen wheat-like advanced-generation triticale x wheat derivatives, having tetraploid wheat cytoplasm from triticale, were reciprocally crossed with three improved bread wheats, and the resulting F₁s were evaluated for determining the comparative performance of the bread wheat and triticale cytoplasms for different traits. Significant reciprocal differences in the mean performance were observed for days to heading, days to maturity, spikes/plant, flag-leaf area, peduncle length, plant height, spike length, grains/spike, 1,000-grain weight, grain yield and grain protein content, and most of them were in favour of hexaploid wheat cytoplasm. However, this superiority of the hexaploid cytoplasm was not universal for a particular trait, implying that the differences in the performance of the evaluated reciprocal crosses depended not solely on the cytoplasmic background, but also on the interplay of the specific genotype with the cytoplasm.     

Isolation and characterisation of microsatellites from hexaploid bread wheat

 The development of large panels of simple-to-analyse genetic markers for tagging agronomically important genes and diversity studies in hexaploid bread wheat is an important goal in applied cereal genetic research. We have isolated and sequenced over 200 clones containing microsatellites from the wheat genome and have tested 153 primer pairs for genetic polymorphism using a panel of ten wheat varieties, including the parents of our main mapping cross. A subset comprising 49 primer pairs detects 76 loci, of which 74 can be unequivocably allocated to one of the wheat chromosomes. A relatively low frequency of the loci detected are from the D genome, and these loci show less polymorphism than those from the A and B genomes. Generally, the microsatellites show high levels of genetic polymorphism and an average of 3.5 alleles per locus with an average polymorphism information content (PIC), value of 0.51. The observed levels of polymorphism are positively correlated with the length of the microsatellite repeats. A high proportion, approximately two-thirds, of primer pairs designed to detect simple sequence repeat (SSR) variation in wheat do not generate the expected amplification products and, more significantly, often generate unresolvable PCR products. In general, our results agree closely with those obtained from other recent studies using microsatellites in plants. Received: 19 March 1996 / Accepted: 28 June 1996     

The origin and meiotic behaviour of hexaploid northern wheatgrass (Agropyron dasystachyum)

The occurrence of hexaploid (2n = 6x = 42) forms in some otherwise natural tetraploid populations of Agropyron dasystachyum (2n = 4x = 28) was cytologically detected and studied. The hexaploid plants are morphologically similar to the tetraploids except for a small reduction in the anther size. The general survey of chromosome numbers of natural Northern Wheatgrass (A. dasystachyum 2n = 4x = 28) populations derived from eight different regions of Alberta indicated that the occurrence of hexaploid variants was not restricted to a single locality. A comparative study of chromosome pairing in the natural and the synthetic hexaploids revealed that the naturally occurring 42-chromosomed plants of A. dasystachyum originated as a result of fertilization between unreduced (SSHH) and the natural (SH) gametes, both coming from the tetraploid form of A. dasystachyum. Based on chromosome pairing, the genomes of the natural hexaploid A. dasystachyum have been designated as SSSHHH. The natural hexaploids appear to intercross among themselves and also with tetraploids producing euploid and aneuploid hybrids. The possible evolutionary significance of these findings is briefly discussed.     

Genes responding to vernalization in hexaploid wheat

Genotype-specific gene expression in response to vernalization in common wheat was examined by the differential display method. Two near-isogenic lines of Vrn-A1 ( Vrn-A1 for the spring type and vrn-A1 for the winter type) were treated by vernalization of developing embryos in detached-ear cultures. This treatment was effective to promote vrn-A1 genotypes to head at a time equivalent to that of Vrn-A1. Differential cDNA fragments were isolated by the RT-PCR method from embryos subjected to vernalization treatments for 2- and 4-weeks at DAP10 and DAP20 stages, respectively. Among 110 differential cDNA fragments isolated, 48 were examined for their chromosomal locations and designated as wec ( wheat- embryo cold treatment) genes. Seven wec genes showed genotype-specific expression in response to vernalization. The statistical analysis utilizing two recombinant inbred lines showed that four wec genes were significantly associated with heading factors.