Diploid Wheatgrass Research Articles

Aegilops crassa Boiss. repeatome characterized using low-coverage NGS as a source of new FISH markers: Application in phylogenetic studies of the Triticeae.

Aegilops crassa Boiss. is polyploid grass species that grows in the eastern part of the Fertile Crescent, Afghanistan, and Middle Asia. It consists of tetraploid (4x) and hexaploid (6x) cytotypes (2n = 4x = 28, D1D (Abdolmalaki et al., 2019) XcrXcr and 2n = 6x = 42, D1D (Abdolmalaki et al., 2019) XcrXcrD2D (Adams and Wendel, 2005), respectively) that are similar morphologically. Although many Aegilops species were used in wheat breeding, the genetic potential of Ae. crassa has not yet been exploited due to its uncertain origin and significant genome modifications. Tetraploid Ae. crassa is thought to be the oldest polyploid Aegilops species, the subgenomes of which still retain some features of its ancient diploid progenitors. The D1 and D2 subgenomes of Ae. crassa were contributed by Aegilops tauschii (2n = 2x = 14, DD), while the Xcr subgenome donor is still unknown. Owing to its ancient origin, Ae. crassa can serve as model for studying genome evolution. Despite this, Ae. crassa is poorly studied genetically and no genome sequences were available for this species. We performed low-coverage genome sequencing of 4x and 6x cytotypes of Ae. crassa, and four Ae. tauschii accessions belonging to different subspecies; diploid wheatgrass Thinopyrum bessarabicum (Jb genome), which is phylogenetically close to D (sub)genome species, was taken as an outgroup. Subsequent data analysis using the pipeline RepeatExplorer2 allowed us to characterize the repeatomes of these species and identify several satellite sequences. Some of these sequences are novel, while others are found to be homologous to already known satellite sequences of Triticeae species. The copy number of satellite repeats in genomes of different species and their subgenome (D1 or Xcr) affinity in Ae. crassa were assessed by means of comparative bioinformatic analysis combined with quantitative PCR (qPCR). Fluorescence in situ hybridization (FISH) was performed to map newly identified satellite repeats on chromosomes of common wheat, Triticum aestivum, 4x and 6x Ae. crassa, Ae. tauschii, and Th. bessarabicum. The new FISH markers can be used in phylogenetic analyses of the Triticeae for chromosome identification and the assessment of their subgenome affinities and for evaluation of genome/chromosome constitution of wide hybrids or polyploid species.

Development and molecular cytogenetic characterization of Thinopyrum bessarabicum introgression lines in hexaploid and tetraploid wheats.

A variety of Thinopyrum bessarabicum introgressions in both hexaploid and tetraploid wheats were generated and characterized by molecular cytogenetic analysis. Six wheat-J genome recombinants were identified with ND-FISH and GISH. Diploid wheatgrass, Thinopyrum bessarabicum (2n = 2x = 14, EbEb or JbJb or JJ), is a well-known alien source of salinity tolerance and disease resistance for wheat improvement. The true genetic potential and effect of such introgressions into wheat can be best studied in chromosomal addition or substitution lines. Here, we report the generation and characterization of various categories of Th. bessarabicum derivatives in both hexaploid and tetraploid cultivated wheats. Sequential non-denaturing fluorescence in situ hybridization (ND-FISH) and genomic in situ hybridization (GISH) are robust techniques to visualize the size of alien introgressions and breakpoints. We identified a complete set of monosomic addition lines into both bread wheat and durum wheat, except for 7J in durum wheat, by sequential ND-FISH and GISH. We also characterized alien derivatives belonging to various classes including mono-telosomic additions, disomic additions, monosomic substitutions, double monosomic substitutions, monosomic substitution-monosomic additions, double monosomic additions, and multiple monosomic additions into both bread and durum wheats. In addition, various wheat-Th. bessarabicum recombinant chromosomes were also detected in six alien derivatives. These wheat-Th. bessarabicum derivatives will provide useful cytogenetic resources for improvement of both hexaploid and tetraploid wheats.

Genome-wide introgression from a bread wheat × Lophopyrum elongatum amphiploid into wheat.

We introgressed wheatgrass germplasm from the octoploid amphiploid Triticum aestivum× Lophopyrum elongatum into wheat by manipulating the wheat Ph1 gene and discovered and characterized 130 introgression lines harboring single or, in various combinations, complete and recombined L. elongatum chromosomes. Diploid wheatgrass Lophopyrum elongatum (genomes EE) possesses valuable traits for wheat genetics and breeding. We evaluated several strategies for introgression of this germplasm into wheat. To detect it, we developed and validated multiplexed sets of Sequenom MassARRAY single nucleotide polymorphism (SNP) markers, which differentiated disomic and monosomic L. elongatum chromosomes from wheat chromosomes. We identified 130 introgression lines (ILs), which harbored 108 complete and 89 recombined L. elongatum chromosomes. Of the latter, 59 chromosomes were recombined by one or more crossovers and 30 were involved in centromeric (Robertsonian) translocations or were telocentric. To identify wheat chromosomes substituted for or recombined with L. elongatum chromosomes, we genotyped the ILs with the wheat 90-K Infinium SNP array. We found that most of the wheat 90-K probes correctly detected their targets in the L. elongatum genome and showed that some wheat SNPs are ancient and had originated prior to the divergence of the wheat and L. elongatum lineages. Of the 130 ILs, 52% were homozygous for Ph1 deletion and thus are staged to be recombined further. We failed to detect in the L. elongatum genome the 4/5 reciprocal translocation that has been reported in Thinopyrum bessarabicum and several other Triticeae genomes.

Molecular-cytogenetic analysis of diploid wheatgrass Thinopyrum bessarabicum (Savul. and Rayss) A. Löve.

Thinopyrum bessarabicum (T. Săvulescu & T. Rayss, 1923) A. Löve, 1980 is diploid (2n=2x=14, JJ or EbEb), perennial self-fertilizing rhizomatous maritime beach grass, which is phylogenetically close to another diploid wheatgrass species, Agropyron elongatum (N. Host, 1797) P. de Beauvois, 1812. The detailed karyotype of Th. bessarabicum was constructed based on FISH with six DNA probes representing 5S and 45S rRNA gene families and four tandem repeats. We found that the combination of pAesp_SAT86 (= pTa-713) probe with pSc119.2 or pAs1/ pTa-535 allows the precise identification of all J-genome chromosomes. Comparison of our data with the results of other authors showed that karyotypically Th. bessarabicum is distinct from A. elongatum. On the other hand, differences between the J-genome chromosomes of Th. bessarabicum and the chromosomes of hexaploid Th. intermedium (N. Host, 1797) M. Barkworth & D.R. Dewey, 1985 and decaploid Th. ponticum (J. Podpěra, 1902) Z.–W. Liu & R.–C. Wang, 1993 in the distribution of rDNA loci and hybridization patterns of pSc119.2 and pAs1 probes could be an indicative of (1) this diploid species was probably not involved in the origin of these polyploids or (2) it could has contributed the J-genome to Th. intermedium and Th. ponticum, but it was substantially modified over the course of speciation

Molecular Cytogenetic Characterization of two Triticum-Secale-Thinopyrum Trigeneric Hybrids Exhibiting Superior Resistance to Fusarium Head Blight, Leaf Rust, and Stem Rust Race Ug99.

Fusarium head blight (FHB), leaf rust, and stem rust are the most destructive fungal diseases in current world wheat production. The diploid wheatgrass, Thinopyrum elongatum (Host) Dewey (2n = 2x = 14, EE) is an excellent source of disease resistance genes. Two new Triticum–Secale–Thinopyrum trigeneric hybrids were derived from a cross between a hexaploid triticale (X Triticosecale Wittmack, 2n = 6x = 42, AABBRR) and a hexaploid Triticum trititrigia (2n = 6x = 42, AABBEE), were produced and analyzed using genomic in situ hybridization and molecular markers. The results indicated that line RE21 contained 14 A-chromosomes, 14 B-chromosomes, three pairs of R-chromosomes (4R, 6R, and 7R), and four pairs of E-chromosomes (1E, 2E, 3E, and 5E) for a total chromosome number of 2n = 42. Line RE62 contained 14 A-chromosomes, 14 B-chromosomes, six pairs of R-chromosomes, and one pair of translocation chromosomes between chromosome 5R and 5E, for a total chromosome number of 2n = 42. At the seedling and adult growth stages under greenhouse conditions, line RE21 showed high levels of resistance to FHB, leaf rust, and stem rust race Ug99, and line RE62 was highly resistant to leaf rust and stem rust race Ug99. These two lines (RE21 and RE62) display superior disease resistance characteristics and have the potential to be utilized as valuable germplasm sources for future wheat improvement.

Molecular cytogenetic (FISH) and genome analysis of diploid wheatgrasses and their phylogenetic relationship.

This paper reports detailed FISH-based karyotypes for three diploid wheatgrass species Agropyron cristatum (L.) Beauv., Thinopyrum bessarabicum (Savul.&Rayss) A. Löve, Pseudoroegneria spicata (Pursh) A. Löve, the supposed ancestors of hexaploid Thinopyrum intermedium (Host) Barkworth & D.R.Dewey, compiled using DNA repeats and comparative genome analysis based on COS markers. Fluorescence in situ hybridization (FISH) with repetitive DNA probes proved suitable for the identification of individual chromosomes in the diploid JJ, StSt and PP genomes. Of the seven microsatellite markers tested only the (GAA)n trinucleotide sequence was appropriate for use as a single chromosome marker for the P. spicata AS chromosome. Based on COS marker analysis, the phylogenetic relationship between diploid wheatgrasses and the hexaploid bread wheat genomes was established. These findings confirmed that the J and E genomes are in neighbouring clusters.

Durum wheat genetic stocks involving chromosome 1E of diploid wheatgrass: resistance to Fusarium head blight

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) is the preferred wheat for preparing pasta products. Current durum cultivars have little resistance to Fusarium head blight (FHB), or scab, a ravaging fungal disease. In our Durum Germplasm Enhancement (DGE) project, we previously showed that chromosome 1E of diploid wheatgrass Lophopyrum elongatum (Host) A. Love (2n = 2x = 14; EE genome) is an excellent source of FHB resistance. Through hybridization of this grass with the durum cultivar Langdon, coupled with manipulation of chromosome pairing and selection, we added the chromosome 1E pair into the durum genome and produced a fertile durum 1E addition line, called DGE-1. Also by substituting 1E for the durum homoeologues 1A or 1B, we produced, two fertile disomic substitution lines, 1E(1A) and 1E(1B), which were designated as DGE-2 and DGE-3, respectively. The level of FHB resistance of the genetic stocks was studied in the greenhouse and in the field at Prosper, North Dakota. In the greenhouse, the 1E addition showed 32.15 % infection and was better than Langdon at 58.73 %, but not significantly different from 1E(1A) disomic substitution at 45.60 % infection. The 1E(1B) disomic substitution (88.29 % infection) had the highest FHB infection. Under natural conditions in the field, the observed infection rates were essentially similar. Among the three genetic stocks, the 1E addition DGE-1 had the lowest level of infection (at 10 %) followed by the substitution 1E(1A) at 20 %, and the substitution E(1B) at 70 %. The parental cultivar Langdon had 15 % FHB infection. The genetic stocks of durum may help produce several more alien addition and substitution lines involving different chromosomes and may help locate sources of FHB resistance.

Synthesis and Characterization of Advanced Durum Wheat Hybrids and Addition Lines with Thinopyrum Chromosomes

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) is a natural hybrid-an allotetraploid between 2 wild species, Triticum urartu Tumanian (AA genome) and Aegilops speltoides Tausch (BB genome). Even at the allotetraploid level, durum wheat can tolerate chromosomal imbalance, for example, addition of alien chromosome 1E of diploid wheatgrass, Lophopyrum elongatum. Therefore, one way to broaden its genetic base is to add a desirable chromosome(s) from diploid wild relatives. We attempted chromosomal engineering with chromosomes of a diploid wheatgrass, Thinopyrum bessarabicum-a source of resistance to some diseases including Fusarium head blight. Several advanced hybrids and alien addition lines were studied using traditional cytology, multicolor fluorescent genomic in situ hybridization, and molecular markers. Hybrid derivatives varied in chromosome number from F1 to F8 generations and in backcross generations. In advanced generations, we exercised selection against 28-chromosome plants and in favor of 30-chromosome plants that helped recover 14 addition lines in the F8 generation, as indicated by the absence of segregation for 29-chromosome plants. Disomic additions showed regular meiosis with 15 bivalents, 14 of durum wheat, and 1 of Th. bessarabicum. The addition lines will facilitate further chromosome engineering work on durum wheat for broadening its genetic base.

Registration of DGE‐3, a Durum Wheat Disomic Substitution Line 1E(1B) Involving a Wheatgrass Chromosome

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) alien disomic substitution 1E(1B) line DGE‐3 (Reg. No. GS‐172, PI 665473) was developed by the USDA‐ARS, Northern Crop Science Lab, Cereal Crops Research Unit, Fargo, ND and released in 2012. It was derived from the durum alien disomic addition line DGE‐1 (2n = 28 + 2) having 28 durum chromosomes and the chromosome pair 1E of diploid wheatgrass, Lophopyrum elongatum (Host) Á. Löve. The pedigree of DGE‐3 is PI 645483/‘Langdon’ 1D(1B)*5. By crossing DGE‐1 (PI 645483) with durum disomic substitution line 1D(1B), we produced hybrid derivatives with univalents of chromosomes 1B, 1D, and 1E. We selfed the hybrid derivatives five times and screened each generation for durum homoeologues 1A and 1B. We tested these hybrid derivatives for the presence of the alien chromosome 1E and for the absence of 1D. Using the chromosome‐specific molecular marker Xwmc333 for identifying chromosome 1A, Xwgm18 for 1B, Xwmc147 for 1D, and Xedm17 for 1E, we isolated a durum disomic alien substitution line 1E(1B), which is fertile and stable and has been released as a new genetic stock, DGE‐3. This substitution line has 2n = 28 chromosomes that consist of 26 durum chromosomes plus the wheatgrass chromosome pair, 1E, which compensates for the missing 1B pair of Langdon. The disomic substitution forms 14 bivalents and is meiotically regular and fertile.

Registration of DGE‐2, a Durum Wheat Disomic Alien Substitution Line 1E(1A) Involving a Diploid Wheatgrass Chromosome

The durum wheat (Triticum turgidum L., 2n = 2x = 28; AABB) alien disomic substitution 1E(1A) line DGE‐2 (Reg. No. GS‐171,PI 663216) was developed by the USDA‐ARS, Cereal Crops Research Unit, Northern Crop Science Lab, Fargo, ND and released in 2011. Earlier, we produced and released a durum alien disomic addition line DGE‐1 (2n = 30; PI 645483) that incorporated chromosome 1E of a diploid wheatgrass, Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE). We crossed DGE‐1 with ‘Langdon’ (CItr 13165) disomic substitution line 1D(1A) and produced F1 hybrid derivatives with chromosomes 1A, 1D, and 1E in a single dose. We selfed these hybrid derivatives five times and screened each generation for homoeologous group‐1 chromosomes 1A and 1B. At the same time, these hybrid derivatives were tested for the presence of 1E and absence of 1D. Using the chromosome‐specific molecular markers Xwmc333 for identifying chromosome 1A, Xwgm18 for 1B, Xwmc147 for 1D, and Xedm17 for 1E, we isolated a stable disomic alien substitution line 1E(1A), which has been released as a new genetic stock, DGE‐2. The pedigree of DGE‐2 is DGE‐1 (2n = 28 + 2; PI 645483)/Langdon 1D(1A)*5. This unique disomic alien substitution line DGE‐2 has 2n = 28 chromosomes, in which the wheatgrass chromosome pair, 1E, compensates for the 1A pair of the durum cultivar Langdon. The disomic substitution has regular meiosis and is fertile. With a unique chromosomal constitution and a unique allele Glu‐E1b, DGE‐2 may be useful in basic research.

Synthesis and cytological analyses of hybrids between hexaploid wheat, with and without Ph1, and diploid wheatgrass

The usefulness of wide hybridization in genetic enhancement of crop plants like wheat, Triticum aestivum L. (2n = 6x = 42; AABBDD genomes), is well documented. Diploid wheatgrass, Lophopyrum elongatum (Host) A. Love (2n = 2x = 14; EE genome), is a source of several desirable traits including Fusarium head blight resistance. The objective of this study was to report on the synthesis and cytological analyses of wheat × wheatgrass hybrids and highlight homoeologous pairing involving the wheat and wheatgrass chromosomes. We hybridized wheatgrass with two important, crossable cultivars, ‘Chinese Spring,’ and ‘Fukohokomugi,’ of bread wheat and produced 11 tetraploid (2n = 4x = 28; ABDE) and two pentaploid (2n = 5x = 28; ABDEE) hybrids. To help promote homoeologous pairing and hence genetic recombination between the wheat and grass chromosomes, we also used the Chinese Spring mutant ph1bph1b. Using molecular markers, we readily detected intergeneric hybrids without Ph1. The hybrids without Ph1 showed multivalent formation involving wheat and grass chromosomes. However, the lack of Ph1 produced a much higher homoeologous pairing in the haploid chromosome complement in the CS ph1bph1b × wheatgrass hybrids than in the disomic complement of CS ph1bph1b. The pentaploid hybrids resulted from the fusion of a normal 21-chromsome gamete of the wheat parent with an unreduced, 14-chromsome gamete of diploid wheatgrass. These hybrids showed a remarkable degree of Ph1-enforced preferential pairing among the homologous wheatgrass chromosomes. Varying degrees of homoeologous pairing in various hybrids were detected that could facilitate alien gene transfer into wheat.

Cytological and Molecular Characterization of Homoeologous Group-1 Chromosomes in Hybrid Derivatives of a Durum Disomic Alien Addition Line

Earlier, we produced a stable Fusarium head blight (FHB)-tolerant durum wheat (Triticum turgidum L.) alien disomic addition line, DGE-1 (released in 2008), incorporating chromosome 1E of diploid wheatgrass [Lophopyrum elongatum (Host) A. Love; 2n = 2x = 14; EE]. For stable FHB resistance, the ultimate goal would be to transfer resistance from 1E into the durum chromosome 1A or 1B. Such transfer is more likely to occur when these target chromosomes are in a single dose. Therefore, we crossed DGE-1 with ‘Langdon’ substitution lines 1D(1A) and 1D(1B) and produced hybrid derivatives with chromosomes 1A, 1B, 1D, and 1E in a single dose. As an important fi rst step, we standardized a method to readily identify these group-1 chromosomes. Multicolor fl uorescent genomic in situ hybridization that we standardized earlier is useful for such identifi cation but is tedious and expensive. To identify these chromosomes more expeditiously and economically in a large plant population, we also used chromosome-specifi c molecular markers and identifi ed each of the group-1 chromosomes. We used marker Xwmc333 to identify chromosome 1A, Xwgm18 for 1B, Xwmc147 for 1D, and Xedm17 for 1E. Xedm17, which profi les chromosome 1E, also generated two characteristic bands for chromosome 1D and may therefore be useful in identifying both chromosomes simultaneously. DURUM WHEAT (Triticum turgidum L.; 2n = 4x = 28; AABB) is an important cereal used for human consumption in the United States, Canada, and most European countries, including Italy, Turkey, France, Romania, and Ukraine. On the evolutionary ladder, durum wheat is a forerunner of bread wheat (Triticum aestivum L.; 2n = 6x = 42; AABBDD) and evolved in nature long before the latter (see Jauhar, 2006). Durum wheat is a natural hybrid, having resulted from hybridization between related wild species in conjunction with doubling of chromosome number. Th us, it enjoys the benefi ts of both polyploidy and hybridity. It has a unique cytogenetic architecture and its chromosomes can be divided into seven homoeologous groups of two chromosomes each (Fig. 1). Th e chromosomes within a homoeologous group are genetically and evolutionarily related. Durum wheat can tolerate addition of certain chromosomes, of related species, syntenic to those within a homoeologous group. A related species, diploid wheatgrass [Lophopyrum elongatum (Host) A. Love; 2n = 2x = 14; EE genome] is an excellent source of Fusarium head blight (FHB) resistance (Jauhar and Peterson, 1998). In our earlier work on durum germplasm enhancement (DGE), we produced a stable alien disomic addition line, DGE-1, incorporating chromosome 1E of L. elongatum (Jauhar and Peterson, 2008; Jauhar et al., 2009). DGE-1 is the fi rst alien addition line of its kind with a novel source of FHB resistance from chromosome 1E. Th e ultimate goal would be to transfer FHB resistance from the added alien chromosome 1E into the durum chromosome complement. Homoeologous group-1 chromosomes 1A and/or 1B of durum wheat would naturally be the logical Published in The Plant Genome 4:102–109. Published 21 June 2011. doi: 10.3835/plantgenome2011.01.0002 © Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA An open-access publication All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. USDA-ARS, Northern Crop Science Lab., Fargo, ND 58102. Mention of trade names or commercial products in this publication is solely to provide specifi c information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. Received 26 Aug. 2010. *Corresponding author (prem.

Chromosome Engineering of Durum Wheat with Alien Chromatin of Diploid Wheatgrass

Durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) is an important cereal widely used for human consumption. It is the choice wheat for preparing pasta products. Current durum cultivars have little resistance to Fusarium head blight (FHB), or scab, a ravaging fungal disease caused by the fungal pathogen Fusarium graminearum Schwabe. We showed earlier that diploid wheatgrass (Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) is an excellent source of FHB resistance, which could be transferred to commercial durum cultivars by hybridization coupled with manipulation of chromosome pairing. We obtained homoeologous pairing (i.e., pairing between wheat and alien chromosomes) in intergeneric hybrids because of the wheatgrass-induced suppression of the pairing-regulating gene Ph1 of wheat, leading to alien chromatin integration into the durum genome. Adopting this chromosome engineering technology, we have transferred diploid wheatgrass chromatin into the durum genome. We have produced fertile hybrid derivatives with varying degrees of FHB resistance. Some derivatives showed only 7.6% infection compared with 72.0% in the parental durum cultivar. Fluorescent genomic in situ hybridization (fl-GISH) analysis was used to confirm the integration of alien chromatin into the durum complement.

Cytogenetic and molecular characterization of a durum alien disomic addition line with enhanced tolerance to Fusarium head blight

Current durum wheat (Triticum turgidum L. subsp. durum (Desf.)) cultivars have little or no resistance to Fusarium head blight (FHB), a ravaging disease of cereal crops. A diploid wheatgrass, Lophopyrum elongatum (Host) A. Löve (2n = 2x = 14, EE genome), is an excellent source of FHB resistance. Through an extensive intergeneric hybridization using durum cultivar Langdon, we have developed a disomic alien addition line, named DGE-1 (2n = 28 + 2), with a wheatgrass chromosome pair. We used a unique method for isolating the addition line taking advantage of unreduced gametes functioning in Langdon x L. elongatum F1 hybrids in their first backcross to the Langdon parent, resulting in 35-chromosome plants from which we derived DGE-1. The addition line DGE-1 has a plant type similar to its Langdon parent, although it is shorter in height with narrower leaves and shorter spikes. It is meiotically and reproductively stable, generally forming 15 bivalents with two chiasmata each. The alien chromosome pair from the grass confers FHB resistance to the addition line, which has less than 21% infection on the visual scale, mean = 6.5%. Using various biochemical and molecular techniques (Giemsa C-banding, fluorescent genomic in situ hybridization (fl-GISH), chromosome-specific simple sequence repeat (SSR) markers, targeted region amplified polymorphism (TRAP) markers, and sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE)), we have shown that the extra chromosome involved is 1E of L. elongatum. This is the first time that FHB resistance has been discovered on chromosome 1E. We have established a chromosome-specific marker for 1E that may be used to screen fertile hybrid derivatives and durum addition lines for this chromosome that confers FHB resistance.

Synthesis of an FHB-resistant durum disomic alien addition line with a pair of diploid wheatgrass chromosomes

Durum wheat ( Triticum turgidum L., 2 n = 4 x = 28; AABB genomes) is an important cereal crop widely used for human consumption. Fusarium head blight (FHB), or scab, caused by the fungus Fusarium graminearum Schwabe, is a serious disease of durum wheat. Current durum cultivars have very little or no FHB resistance. A wild relative, diploid wheatgrass Lophopyrum elongatum (Host) A. Love (2 n = 2 x = 14; EE genome) is an excellent source of resistance. By crossing durum wheat with L. elongatum we produced F 1 hybrids that were male sterile. By backcrossing the F1 hybrids to the durum parent, followed by selfing, we obtained several fertile hybrid derivatives with FHB resistance. We isolated a disomic addition line (2 n = 28 + 2) with a pair of L. elongatum chromosomes. This alien addition line is meiotically regular and hence reproductively stable. The addition line is FHB-resistant with a mean infection of 6.5%, while the parental durum has 80% infection. Using various biochemical and molecular techniques ...

Registration of DGE‐1, Durum Wheat Alien Disomic Addition Line with Resistance to Fusarium Head Blight

The durum wheat (Triticum turgidum L.) alien disomic addition line, DGE‐1 (Reg No. GS‐156, PI 645483), was developed by the USDA‐ARS, Cereal Crops Research Unit, Northern Crop Science Laboratory, Fargo, ND and released in 2006. DGE‐1 (2n = 28 + 2) possesses an additional pair of chromosomes from diploid wheatgrass, Lophopyrum elongatum (Host) Á. Löve (2n = 2x = 14; EE genome) conferring resistance to Fusarium head blight (FHB), caused by the fungus Fusarium graminearum Schwabe. The pedigree of DGE‐1 is [(Langdon/L. elongatum//Langdon)*1/Langdon]*8. The (Langdon × L. elongatum) F1 hybrid (2n = 2x = 21; ABE genomes) was backcrossed with the recurrent Langdon parent, then selfed for one generation, and backcrossed again before selfing for several cycles. The addition line with FHB resistance (less than 21% on the visual scale; mean = 6.5% in the generation before release) was obtained by selecting for resistance in each generation after the durum wheat chromosome complement was reconstituted with the added alien chromosome in one and later in double dose. The extra chromosome involved is 1E of L. elongatum

Cytological analyses of hybrids and derivatives of hybrids between durum wheat and Thinopyrum bessarabicum, using multicolour fluorescent GISH*

AbstractThe wheat progenitors and other wild relatives continue to be important sources of genes for agronomically desirable traits, which can be transferred into durum wheat (Triticum turgidum; 2n = 4x = 28; AABB genomes) cultivars via hybridization. Chromosome pairing in durum × alien species hybrids provides an understanding of genomic relationships, which is useful in planning alien gene introgression strategies. Two durum cultivars, ‘Lloyd’ and ‘Langdon’, were crossed with diploid wheatgrass, Thinopyrum bessarabicum (2n = 2x = 14; JJ), to synthesize F1 hybrids (2n = 3x = 21; ABJ) with Ph1. ‘Langdon’ disomic substitution 5D(5B) was used as a female parent to produce F1 hybrids without Ph1, which resulted in elevation of pairing between durum and grass chromosomes – an important feature from the breeding standpoint. The F1 hybrids were backcrossed to respective parental cultivars and BC1 progenies were raised. ‘Langdon’ 5D(5B) substitution × Th. bessarabicum F1 hybrids were crossed with normal ‘Langdon’ to obtain BC1 progeny. Chromosome pairing relationships were studied in F1 hybrids and BC1 progenies using both conventional staining and fluorescent genomic in situ hybridization (fl‐GISH) techniques. Multicolour fl‐GISH was standardized for characterizing the nature and specificity of chromosome pairing: A–B, A–J and B–J pairing. The A–J and B–J pairing will facilitate gene introgression in durum wheat. Multicolour fl‐GISH will help in characterizing alien chromosome segments captured in the durum complement and in their location in the A and/or B genome, thereby accelerating chromosome engineering research.

Hybrid between durum wheat and diploid Thinopyrum bessarabicum

Gross morphological features and chromosome association of the first triploid intergeneric hybrid (2n = 3x = 21; ABJ genomes) between durum wheat, Triticum turgidum L. (2n = 4x = 28; AABB), and diploid wheatgrass, Thinopyrum bessarabicum (Savul. &Rayss) A. Löve (2n = 2x = 14; JJ), are described. Genome relationships are assessed in the presence of the pairing homoeologous gene, Ph1. The hybrid was intermediate in phenotype between the two parents. It inherited the tillering habit, perennial growth habit, and glaucous leaves and stems from the male Thinopyrum parent; spike density and awns of wheat were partially expressed. An average of 13.67% of the chromosome complement paired in metaphase I cells of the hybrid. Mean chromosome associations were 0.07 III + 0.03 ring II + 1.30 rod II + 18.13 I and 1.51 chiasmata per cell, with a mean arm-pairing frequency, c, of 0.107. Because chromosomes of the A and B genomes show very little pairing with each other in the polyhaploids of T. turgidum, it was inferred that most of the bivalents in the hybrid were formed between chromosomes of the A and J and (or) B and J genomes, a welcome feature from the breeding standpoint. Trivalent frequency, albeit low, further indicated intergenomic pairing among A, B, and J. Associations between wheat and Thinopyrum chromosomes may permit intergeneric transfer of genes, which may be accelerated by the use of the ph1c ph1c homoeologous pairing mutant of durum wheat.Key words: intergeneric hybrid, chromosome pairing, genome relationship, Triticum, Ph1 pairing regulator.

Salt Tolerance in the Triticeae: Growth and Solute Accumulation in Leaves ofThinopyrum bessarabicum

Gorham, J., McDonnell, E., Budrewicz, E. and Wyn Jones, R. G. 1985. Salt tolerance in the Triticeae: growth and solute accumulation in leaves of Thinopyrum bessarabicum.—]. exp. Bot. 36:1021-1031. The diploid wheatgrass Thinopyrum bessarabicum was found to withstand prolonged exposure to 350 mol m 3 NaCl in hydroponic culture. During the gradual addition of salt to the external medium, osmotic adjustment was rapidly achieved by the accumulation of Na and CI. Following osmotic adjustment constant leaf Na and CI concentrations were maintained, and K was retained at a high level. Thinopyrum bessarabicum may be described as an osmoconformer, adjusting its internal osmotic pressure to 400-500 mOsmol kg1 above that of the external medium in hydroponic culture. Both slower shoot initiation and reduced leaf length contributed to the reduced growth rates at higher salinities. Leaf width was not affected. Increasing salinity resulted in increases in leaf concentrations of phosphate, glycinebetaine, sucrose and proline, and in decreases in the concentrations of nitrate, sulphate, magnesium, calcium, total amino acids and organic acids. Thinopyrum bessarabicum exhibits salt tolerance characters which may be useful in wheat breeding.