Production and genetic characterization of near-isogenic lines in the bread-wheat cultivar Alpe

Two biotypes of the bread-wheat cultivar Alpe were shown to possess contrasting alleles at each of the glutenin (Glu-B1, Glu-D1, Glu-B3 and Glu-D3) and gliadin (Gli-B1 and Gli-D1) loci on chromosomes 1B and 1D. Fourteen near-isogenic lines (NILs) were produced by crossing these biotypes and used to determine the genetic control of both low-molecular-weight (LMW) glutenin subunits and gliadins by means of one-dimensional or two-dimensional electrophoresis. Genes coding for the B, C and D groups of EMW subunits were found to be inherited in clusters tightly linked with those controlling gliadins. Southern-blot analysis of total genomic DNAs hybridized to a -gliadin-specific cDNA clone revealed that seven NILs lack both the Gli-D1 and Glu-D3 loci on chromosome 1D. Segregation data indicated that these null alleles are normally inherited. Comparison of the null NILs with those possessing allele b at the Glu-D3 locus showed one B subunit, seven C subunits and two D subunits, as fractionated by two-dimensional A-PAGExSDS-PAGE, to be encoded by this allele. Alleles b and k at Glu-B3 were found to code for two C subunits plus eight and six B subunits respectively, whereas alleles b and k at Gli-B1 each controlled the synthesis of two -gliadins, one and two -gliadins. The novel Gli-B5 locus coding for two -gliadins was shown to recombine with the Gli-B1 locus on chromosome 1B. The two-dimensional map of glutenin subunits showed -gliadins encoded at the Gli-A2 locus on chromosome 6A. The use of Alpe NILs in the study of the individual and combined effects of glutenin subunits on dough properties is discussed.Research supported by a grant from the Commission of the European Communities, ECLAIR programme, Contract AGRE 0052     

Use of recombinant inbred lines of wheat for study of associations of high-molecular-weight glutenin subunit alleles to quantitative traits

Summary The high-molecular-weight glutenin subunits (HMW glutenin), encoded by alleles at homoeologous lociGlu-A1,Glu-B1, andGlu-D1 on the long arms of chromosomes1A,1B, and1D of a set of F₈ random recombinant inbred lines (RIL) derived from the bread wheat cross Anza × Cajeme 71, were classified by SDS-PAGE. Anza has poor breadmaking quality and HMW-glutenin subunits (Payne numbers) null (Glu-A1c), 7+8 (Glu-B1b), and 2+12 (Glu-D1a); Cajeme 71 has good quality and 1 (Glu-A1a), 17+18 (Glu-B1i), and 5+10 (Glu-D1d). The combinations of these alleles in the RIL were examined for associations with grain yield and four indicators of grain quality — protein content, yellowberry, pearling index, and SDS sedimentation volume. Data were obtained from a field experiment with three nitrogen fertilization treatments on 48 RIL and the parents. Orthogonal partitioning of the genetic variance associated with the three HMW glutenin subunit loci into additive and epistatic (digenic and trigenic) effects showed strong associations of these loci with grain yield and the indicators of quality; however, the associations accounted for no more than 25% of the differences between the parents. Genetic variance was detected among the RIL, which had the same HMW glutenin genotype for all traits. Epistatic effects were absent for grain yield and yellowberry, but were substantial for grain protein content, pearling index, and SDS sedimentation volume. All three loci had large single-locus additive effects for grain yield, protein, and SDS sedimentation volume. Yellowberry was largely influenced byGlu-B1 andGlu-D1, whereas pearling index was associated withGlu-A1 andGlu-B1. Even though the observed associations-of effects of HMW glutenin loci with the quantitative characters were small relative to the total genetic variability, they are of considerable importance in understanding the genetics of wheat quality, and are useful in the development of new wheat varieties with specific desired characteristics.     

Biochemical and genetic characterization of a monomeric storage protein (T1) with an unusually high molecular weight in Triticum tauschii

The protein named T1, present in Triticum tauschii, was previously characterized as a high-molecular-weight (HMW) glutenin subunit with a molecular size similar to that of the y-type glutenin subunit-10 of Triticum aestivum. This protein was present along with other HMW glutenin subunits named 2^t and T2, and was considered as part of the same allele at the Glu-D ^t 1 locus of T. tauschii. This paper describes a re-evaluation of this protein, involving analyses of a collection of 173 accessions of T. tauschii, by SDS-PAGE of glutenin subunits after the extraction of monomeric protein. No accessions were found containing the three HMW glutenin subunits. On the other hand, 17 lines with HMW glutenin subunits having electrophoretic mobilities similar to subunits 2^t and T2 were identified. The absence of T1 protein in these gel patterns has shown that protein T1 is not a component of the polymeric protein. Rather, the T1 protein is an ω-gliadin with an unusually high-molecular-weight. This conclusion is based on acidic polyacrylamide gel electrophoresis (A-PAGE), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and two-dimensional gel electrophoresis (A-PAGE+ SDS-PAGE), together with analysis of its N-terminal amino-acids sequence. The inheritance of ω-gliadin T1 was studied through analyses of gliadins and HMW glutenins in 106 F₂ grains of a cross between synthetic wheat, L/18913, and the wheat cv Egret. HMW glutenin subunits and gliadins derived from T. tauschii (Glu-D ^t 1 and Gli-D ^t 1) segregated as alleles of the Glu-D1 and Gli-D1 loci of bread wheat. A new locus encoding the ω-gliadin T1 was identified and named Gli-DT1. The genetic distance between this new locus and those of endosperm proteins encoded at the 1D chromosome were calculated. The Gli-DT1 locus is located on the short arm of chromosome 1D and the map distance between this locus and the Gli-D1 and Glu-D1 loci was calculated as 13.18 cM and 40.20 cM, respectively. Received: 13 October 2000 / Accepted: 18 April 2001     

Phylogenetic relationships of Triticum tauschii the D genome donor to hexaploid wheat

Summary In crosses between T. tauschii (D ^t) accesions, their polymorphic gliadin forms were inherited as blocks of gliadin components -Gli-D ^t1, Gli-D ^t2 — as single Mendelian characters. From the progeny of four tri-parental crosses (test-crosses), HMW glutenin subunits derived from T. tauschii (Glu-D ^t1) segregated as alleles of the Glu-D1 locus in bread wheat. In three of the tri-parental crosses, a small proportion (2.5%) of the progeny with atypical segregation patterns, were identified through somatic chromosome counts, to be aneuploids (1.9% hypoploids and 0.6% hyperploids). Chromosomal mapping studies revealed that the synteny of genes for HMW glutenin subunits and gliadins in T. tauschii are conserved in the D genome homologue (chromosome 1D) of T. aestivum. The map distance between the Glu-D1/-D ^t1 and Gli-D1/-D ^t1 loci was calculated to be 63.5 cM, while a linkage to the centromere of 7.7–9.7 cM was estimated for the Glu-D1/-D ^t1 locus.     

Characterization of heterotic quantitative trait loci in maize by evaluation of near-isogenic lines and their crosses at two competition levels

In a previous study on a maize (Zea mays L.) population of recombinant inbreds derived from B73 × H99, we identified several quantitative trait loci (QTL) for agronomic traits with high dominance-additive ratio. Then, for four of these QTL, we developed families of near-isogenic lines (NILs) homozygous either for the QTL allele from B73 (BB) or from H99 (HH); for two of these QTL, the NILs’ families were produced in two different genetic backgrounds. The present study was conducted to: (1) characterize these QTL for agronomic traits and (2) verify whether their effects were influenced by the genetic background, inbreeding level and plant density (PD). The six NILs’ families were tested across 3 years and in three experiments at different inbreeding levels as NILs per se and their reciprocal crosses (Experiment 1), NILs crossed to related inbreds B73 and H99 (Experiment 2) and NILs crossed to four unrelated inbreds (Experiment 3). Experiment 2 was conducted at two PDs (4.5 and 9.0 plants m⁻²). Results of Experiments 1 and 2 confirmed previous findings as to QTL effects, with dominance–additive ratio superior to 1 for several traits; as a tendency, dominance effects were more pronounced in Experiment 1. The QTL effects were also confirmed in Experiment 3. The interactions involving QTL effects, families and PD were generally negligible, suggesting a certain stability of the QTL. Results emphasize the importance of dominance effects for these QTL, suggesting that they might deserve further studies, using the NILs’ families and their crosses as base materials.     

Genetic control of wheat quality: interactions between chromosomal regions determining protein content and composition, dough rheology, and sponge and dough baking properties

While the genetic control of wheat processing characteristics such as dough rheology is well understood, limited information is available concerning the genetic control of baking parameters, particularly sponge and dough (S&D) baking. In this study, a quantitative trait loci (QTL) analysis was performed using a population of doubled haploid lines derived from a cross between Australian cultivars Kukri × Janz grown at sites across different Australian wheat production zones (Queensland in 2001 and 2002 and Southern and Northern New South Wales in 2003) in order to examine the genetic control of protein content, protein expression, dough rheology and sponge and dough baking performance. The study highlighted the inconsistent genetic control of protein content across the test sites, with only two loci (3A and 7A) showing QTL at three of the five sites. Dough rheology QTL were highly consistent across the 5 sites, with major effects associated with the Glu-B1 and Glu-D1 loci. The Glu-D1 5 + 10 allele had consistent effects on S&D properties across sites; however, there was no evidence for a positive effect of the high dough strength Glu-B1-al allele at Glu-B1. A second locus on 5D had positive effects on S&D baking at three of five sites. This study demonstrated that dough rheology measurements were poor predictors of S&D quality. In the absence of robust predictive tests, high heritability values for S&D demonstrate that direct selection is the current best option for achieving genetic gain in this product category. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Recombination mapping of some chromosome 1A-, 1B-, 1D- and 6B-controlled gliadins and low-molecular-weight glutenin subunits in common wheat

 Inheritance of low-molecular-weight glutenin subunits (LMW GS) and gliadins was studied in the segregating progeny from several crosses between common wheat genotypes. The occurrence of a few recombinants in the F₂ grains of the cross Skorospelka Uluchshennaya×Kharkovskaya 6 could be accounted for by assuming that the short arm of chromosome 1D contains two tightly linked loci each coding for at least one gliadin plus one C-type LMW GS. These loci were found to recombine at a frequency of about 2%, and to be linked to the Glu-D3 locus coding for B-type LMW GS. Some proteins showing biochemical characteristics of D-type or C-type LMW GS were found to be encoded by the Gli-B1 and Gli-B2 loci, respectively. Strongly stained B-type LMW GS in cvs Skorospelka Uluchshennaya and Richelle were assigned to the Glu-B3 locus, but recombination between this locus and Gli-B1 was not found. Analogously, in the cross Bezostaya 1×Anda, no recombination was found between Gli-A1 and Glu-A3, suggesting the maximum genetic distance between these loci to be 0.97% (P=0.05). A B-type LMW GS in cv Kharkovskaya 6 was assigned to the Glu-B2 locus, with about 25% recombination from the Gli-B1 locus. The present results suggested that alleles at Gli loci may relate to dough quality and serve as genetic markers of certain LMW GS affecting breadmaking quality. Received: 9 July 1996/Accepted: 15 November 1996     

Analysis of diversity of russian and Ukrainian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars for high-molecular-weight glutenin subunits

The allelic diversity of high-moleculat-weght glutenin subunits (HMWGS) in Russian and Ukrainian bread wheat cultivars was analyzed. The diversity of spring wheat cultivars for alleles of the Glu-1 loci is characterized by medium values of the polymorphism polymorphism information content (PIC), and in winter wheats it varies from high at the Glu-A1 locus to low at the Glu-D1 locus. The spring and winter cultivars differ significantly in the frequencies of alleles of the glutenin loci. The combination of the Glu-A1b, Glu-B1c, and Glu-D1a alleles prevails among the spring cultivars, and the combination of the Glu-A1a, Glu-B1c, and Glu-D1d alleles prevails among the winter cultivars. The distribution of the Glu-1 alleles significantly depends on the moisture and heat supply in the region of origin of the cultivars. Drought resistance is associated with the Glu-D1a allele in the spring wheat and with the Glu-B1b allele in the winter wheat. The sources of the Glu-1 alleles were identified in the spring and wheat cultivars. The analysis of independence of the distribution of the spring and winter cultivars by the market classes and by the alleles of the HMWGS loci showed a highly significant association of the alleles of three Glu-1 loci with the market classes in foreign cultivars and independence or a weak association in the Russian and Ukrainian cultivars. This seems to be due to the absence of a statistically substantiated system of classification of the domestic cultivars on the basis of their quality.     

The genetic control of seven isozymic loci in Vicia faba L. Identification of lines and estimates of outcrossing rates between plants pollinated by bumble bees

A simplified and non-destructive method using starch gel electrophoresis has been developed on seeds to identify inbred lines of Vicia faba and assess outcrossing rates and gene dispersal in pollination experiments. Six enzyme systems (Alcohol dehydrogenase, Aspartate aminotransferase, Glucose-6-phosphate isomerase, Isocitrate dehydrogenase, Phosphogluconate dehydrogenase and Shikimate dehydrogenase) were analysed from parental lines, crosses performed between lines bearing dissimilar isozyme patterns in pollination cages with Bombus and F₂ progenies obtained from manual selfing of F₁ hybrids. The allozymes at each of the seven studied loci segregated in the expected Mendelian fashion and behaved in a co-dominant manner except for the Adh-2 locus where the only variant was a null allele. No evidence of genetic linkage was observed between at least 13 of the 15 pairs of the studied loci. Percentage of cross fertilisation by Bombus between seven pairs of inbred lines ranged between 1.7% and 28.3%. Pollen transfer between a donor line and a recipient line by two species of Bombus did not lead to differences in outcrossing rates (both about 8%). The new PGD marker with two loci at three alleles each is particularly discriminating and valuable in pollination studies and breeding of V. faba.     

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.     

Low-temperature tolerance and genetic potential in wheat (Triticum aestivum L.): response to photoperiod, vernalization, and plant development

It is frequently observed that winter habit types are more low-temperature (LT) tolerant than spring habit types. This raises the question of whether this is due to pleiotropic effects of the vernalization loci or to the linkage of LT-tolerance genes to these vernalization loci. Reciprocal near-isogenic lines (NILs) for alleles at the Vrn-A1 locus, Vrn-A1 and vrn-A1, determining spring and winter habit respectively, in two diverse genetic backgrounds of wheat (Triticum aestivum L.) were used to separate the effects of vernalization, photoperiod, and development on identical, or near identical, genetic backgrounds. The vrn-A1 allele in the winter lines allowed full expression of genotype dependent LT tolerance potential. The winter allele (vrn-A1) in a very cold tolerant genetic background resulted in 11°C, or a 2.4-fold, greater LT tolerance compared to the spring allele. Similarly, the delay in development caused by short-day (SD) versus long-day (LD) photoperiod in the identical spring habit NIL resulted in an 8.5°C or 2.1-fold, increase in LT tolerance. The duration of time in early developmental stages was shown to underlie full expression of genetic LT-tolerance potential. Therefore, pleiotropic effects of the vernalization loci can explain the association of LT tolerance and winter habit irrespective of either the proposed closely linked Fr-A1 or the more distant Fr-A2 LT-tolerance QTLs. Plant development progressively reduced LT-acclimation ability, particularly after the main shoot meristem had advanced to the double ridge reproductive growth stage. The Vrn-1 genes, or other members of the flowering induction pathway, are discussed as possible candidates for involvement in LT-tolerance repression.     

Characterization and detection of epistatic interactions of 3 QTLs, Hd1, Hd2, and Hd3, controlling heading date in rice using nearly isogenic lines

To characterize quantitative trait loci (QTLs), we used marker-assisted selection (MAS) to develop three nearly isogenic lines (NILs) differing only for the presence of a single, specific QTL (QTL-NILs) –Hd1, Hd2, and Hd3 – for heading date in rice. The three lines contained the chromosomal region of the target QTL from donor variety Kasalath(indica) in the genetic background of var. Nipponbare (japonica). To analyze epistatic interactions in pairs of these QTLs, we also used MAS to develop four combined QTL-NILs with 2 of the 3 QTLs or with all 3. Different daylength treatment testing of the QTL-NILs revealed that the three QTLs control photoperiod sensitivity. Genetic analysis of F₂ populations derived from crosses between the three QTL-NILs with a single QTL using molecular markers revealed the existence of epistatic interactions between Hd1 and Hd2, and Hd2 and Hd3. These interactions were also confirmed by the analysis of combined QTL-NILs under different daylength conditions. The existence of an epistatic interaction between Hd1 and Hd3 was also clarified. Based on these results, we suggest that the Kasalath allele of Hd3 does not affect photoperiod sensitivity by itself but that it is involved in enhancement of the expression of the Nipponbare alleles of Hd1 and Hd2. Received: 22 October 1999 / Accepted: 21 March 2000     

Quality differences between NILs of wheat variety Long 97-586 possessing HMW-GS 7+8 and 7

The high molecular weight glutenin subunits (HMW-GS) 7+8 were introduced into the Long 97–586 (1,7,2+12) wheat variety (Triticum aestivum) by 5 consecutive backcrosses with biochemical marker–assisted selection.Nearly isogenic lines (NILs) of HMW-GS 7 and 7+8 were obtained,and the NILs were planted in the experimental field at the Crop Breeding Institute of Heilongjiang Academy of Agricultural Science in 2004–2006.The field experiments were designed using the two-column contrast arrangement method with six replicates in 2004–2005 and four replicates in 2006.The result of three years experiments showed that the differences between NILs of Long 97–586 with subunit 7 and those with subunits 7+8 in the quality parameters of flour protein content and dry gluten content were negligible (P0.1).However,the differences in some of the quality parameters were remarkably significant (P0.01),including wet gluten content,ratio of wet gluten/dry gluten,gluten index,Zeleny sedimentation,ratio of sedimentation/dry gluten,and the farinogram parameters of water absorption,development time,stability,breakdown time and degree of softening.The difference between NILs with subunits 7+8 and subunit 7 was significant (P0.05) on the alveogram W value and had a critical value (P=0.05) on the alveogram P value in 2006.The results show that HMW-GS 7+8 is far superior to HMW-GS 7 in terms of baking quality.The possibilities of using subunits 7+8 and subunit 7 in breeding strong and weak gluten wheat varieties are discussed in this paper.     

A set of near-isogenic lines of Indica-type rice variety CO 39 as differential varieties for blast resistance

Twenty-seven near-isogenic lines (NILs) with the genetic background of a blast-susceptible variety, CO 39, were developed by repeated backcrossing as a first set of a large number of differential varieties (DVs) with Indica-type genetic background. The NILs included 14 resistance genes—Pish, Pib, Piz-5, Piz-t, Pi5(t), Pik-s, Pik, Pik-h, Pik-m, Pik-p, Pi1, Pi7(t), Pita, and Pita-2—derived from 26 donor varieties. The reaction patterns of NILs against 20 standard isolates from the Philippines were similar to those of blast monogenic lines with the same resistance gene, except for those against two isolates that are avirulent to Pia in the genetic background of CO 39. A genome-wide DNA marker survey revealed that chromosome segments were introgressed in the regions where each resistance gene was previously mapped and most of the other chromosome regions in each NIL were CO 39 type. Segregation analysis of resistance and co-segregation analysis between resistance and DNA markers using F3 populations derived from the crosses between each NIL and the recurrent parent, CO 39, revealed a single-gene control of resistance and association between resistance and target introgressed segments. The morphological characters of each NIL were almost the same as those of the recurrent parent except for some lines, suggesting that these NILs can be used even under tropical conditions where Japonica-type DVs are not suitable for cropping. Thus, these NILs are useful not only as genetic tools for blast resistance study but also as sources of genes for breeding of Indica-type rice varieties.     

Effect of gliadins and HMW and LMW subunits of glutenin on dough properties in the F6 recombinant inbred lines from a bread wheat cross

The storage proteins of 64 F₂-derived F₆ recombinant inbred lines (RILs) from the bread wheat cross Prinqual/Marengo were analyzed. Parents differed at four loci: Gli-B1 (coding for gliadins), Glu-B1 (coding for HMW glutenin subunits), Glu-A3/Gli-A1 (coding for LMW glutenin subunits/gliadins) and Glu-D3 (coding for LMW glutenin subunits). The effect of allelic variation at these loci on tenacity, extensibility and dough strength as measured by the Chopin alveograph was determined. Allelic differences at the Glu-B1 locus had a significant effect on only tenacity. None of the allelic differences at either the Glu-A3/Gli-A1 or Glu-D3 loci had a significant effect on quality criteria. Allelic variation at the Gli-B1 locus significantly affected all of the dough properties. Epistatic effects between some of the loci considered contributed significantly to the variation in dough quality. Additive and epistatic effects each accounted for 15% of the variation in tenacity. Epistasis accounted for 15% of the variation in extensibility, whereas additive effects accounted for 4%. Epistasis accounted for 14% of the variation in dough strength, and additivity for 9%. The relative importance of epistatic effects suggest that they should be included in predictive models when breeding for breadmaking quality.     

Efficient isolation of ion beam-induced mutants for homoeologous loci in common wheat and comparison of the contributions of Glu-1 loci to gluten functionality

Key message

Ion beam mutations can be efficiently isolated and deployed for functional comparison of homoeologous loci in polyploid plants, and Glu - 1 loci differ substantially in their contribution to wheat gluten functionality.

Abstract

To efficiently conduct genetic analysis, it is beneficial to have multiple types of mutants for the genes under investigation. Here, we demonstrate that ion beam-induced deletion mutants can be efficiently isolated for comparing the function of homoeologous loci of common wheat (Triticum aestivum). Through fragment analysis of PCR products from M₂ plants, ion beam mutants lacking homoeologous Glu-A1, Glu-B1 or Glu-D1 loci, which encode high molecular weight glutenin subunits (HMW-GSs) and affect gluten functionality and end-use quality of common wheat, could be isolated simultaneously. Three deletion lines missing Glu-A1, Glu-B1 or Glu-D1 were developed from the original mutants, with the Glu-1 genomic regions deleted in these lines estimated using newly developed DNA markers. Apart from lacking the target HMW-GSs, the three lines all showed decreased accumulation of low molecular weight glutenin subunits (LMW-GSs) and increased amounts of gliadins. Based on the test data of five gluten and glutenin macropolymer (GMP) parameters obtained with grain samples harvested from two environments, we conclude that the genetic effects of Glu-1 loci on gluten functionality can be ranked as Glu-D1 > Glu-B1 > Glu-A1. Furthermore, it is suggested that Glu-1 loci contribute to gluten functionality both directly (by promoting the formation of GMP) and indirectly (through keeping the balance among HMW-GSs, LMW-GSs and gliadins). Finally, the efficient isolation of ion beam mutations for functional comparison of homoeologous loci in polyploid plants and the usefulness of Glu-1 deletion lines for further studying the contribution of Glu-1 loci to gluten functionality are discussed.     

Detection of wheat-alien recombinant chromosomes using co-dominant DNA markers**

A study of homoeologous recombination along almost the complete genetic length of two homoeologous chromosomes in the Triticeae was conducted. Sears' phlb mutant was used to induce homoeologous pairing between chromosomes 7A of common wheat and 7Ai–l of Agropyron intermedium. 390 ph1b ph1b homozygous F₃ progeny were screened using six co-dominant DNA markers (RFLP loci). 63 of the progeny (16%) were putative recombinants, showing dissociation of RFLP markers within the arm(s). Progeny tests of self-fertile putative recombinants confirmed the dissociation phenotypes observed in the F₃ progeny. No recombination could be confirmed in 117 F₃ progeny plants having the Ph1– allele (control population). Frequencies and distribution of chiasmata along the chromosome arm 7AS were analysed using additional RFLP markers. The patterns of recombination between the two homoeologous chromosomes were found similar to those reported for homologous recombination between the same markers on short arms of group 7 chromosomes of Triticeae.     

Stably expressed <Emphasis Type="SmallCaps">d</Emphasis>-genome-derived HMW glutenin subunit genes transformed into different durum wheat genotypes change dough mixing properties

Durum wheat (Triticum turgidum L. var. durum) is traditionally used for the production of numerous types of pasta, and significant amounts are also used for bread-making, particularly in southern Italy. The research reported here centres on the glutenin subunits 1Dx5 and 1Dy10 encoded by chromosome 1D, and whose presence in hexaploid wheats is positively correlated with higher dough strength. In order to study the effects of stable expression of the 1Dx5 and 1Dy10 glutenin subunits in different durum wheat genotypes, four cultivars commonly grown in the Mediterranean area (‘Svevo’, ‘Creso’, ‘Varano’ and ‘Latino’) were co-transformed, via particle bombardment of cultured immature embryos, with the two wheat genes Glu-D1-1d and Glu-D1-2b encoding the glutenin subunits, and a third plasmid containing the bar gene as a selectable marker. Protein gel analyses of T₁ generation seed extracts showed expression of one or both glutenin genes in four different transformed durum wheat plants. One of these transgenic lines, DC2-65, showed co-suppression of all HMW-GS, including the endogenous ones. Transgene stability in the transgenic lines has been studied over four generations (T₁–T₄). Fluorescence in situ hybridization (FISH) analysis of metaphase chromosomes from T₄ plants showed that the integration of transgenes occurred in both telomeric and centromeric regions. The three plasmids were found inserted at a single locus in two lines and in two loci on the same chromosome arm in one line. The fourth line had two transgenic loci on different chromosomes: one with both glutenin plasmids and a different one containing only the construct with the gene encoding the 1Dy10 glutenin subunit. Segregation of these two loci in subsequent generations allowed establishment of two sublines, one containing both 1Dx5 and 1Dy10 and the other containing only 1Dy10. Small-scale quality tests showed that accumulation of Dx5, Dy10 or both in transgenic durum wheat seeds resulted in doughs with stronger mixing characteristics. A. Gadaleta and A. E. Blechl have contributed equally to this work.