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Abstract

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Thinopyrum intermedium, a wild relative of wheat, is an excellent source of disease resistance. Two novel partial amphiploids, 08-47-50 and 08-53-55 (2n = 6x = 42), were developed from wide crosses between durum wheat and Th. intermedium. Meiotic analysis showed that pollen mother cells of the two partial amphiploids formed an average 20.49 bivalents for 08-47-50 and 20.67 bivalents for 08-53-55, indicating that they are basically cytologically stable. GISH analysis revealed that the two partial amphiploids carried different chromosome compositions. 08-47-50 had fourteen chromosomes from Th. intermedium and its alien chromosomes included six St-, four Ee- and four Ee-St translocated chromosomes, whereas 08-53-55 had four St- and ten Ee-St translocated chromosomes. Fungal disease evaluation indicated that both partial amphiploids had a high level of resistance to FHB, leaf rust and stem rust race Ug99. These two novel partial amphiploids with multiple disease resistance could be used as a new source of multiple disease resistance in bread wheat and durum wheat breeding programs.

The ongoing improvement of wheat cultivars is dependent on a continuous supply of genetic variability. Introgression of desirable traits from Triticeae relatives to cultivars by means of wide hybridization has been a successful practice in wheat improvement for biotic and abiotic stress tolerance. A typical and important step in alien gene transfer is the generation of wheat–alien partial amphiploids (Ellneskog-Staam and Merker 2002; Fedak and Han 2005).

Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe (teleomorph Gibberella zeae (Schw.) Petch) is one of the most destructive fungal diseases worldwide, which has caused serious loss in grain yield and quality (Bai and Shaner 1994; Stack 2003). Leaf rust, caused by the fungus Puccinia triticinia Eriks., is the most common and widely distributed of the three wheat rusts. Losses from leaf rust infection are usually less than those from stem rust and stripe rust, but leaf rust causes greater annual losses due to its more frequent and widespread occurrence (McCallum and Seto-Goh 2005). Stem rust caused by the fungus Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn. is a major, devastating disease of bread and durum wheat and historically has caused severe losses to wheat production worldwide. Race Ug99, first identified in Uganda in 1999, has virulence on the gene Sr31 deployed worldwide in many cultivars (Pretorius et al. 2000) and it was redesigned as TTKSK (Jin et al. 2008). Available evidence emerging from the East African countries indicates that Ug99 has exhibited a gradual step-wise range expansion, which is threatening wheat production in the world (Stokstad 2007; Ayliffe et al. 2008).

Durum wheat, Triticum turgidum L. (2n = 4x = 28, AABB), is an important cereal used for preparing pasta and semolina for human consumption worldwide. The wheat grass Thinopyrum intermedium (Host) Barkworth & D.R. Dewey (syn. Elytrigia intermedia (Host) Nevski, Agropyron intermedium (Host) Beauvoir) is a perennial allohexaploid species (2n = 6x = 42, EeEeEeEeStSt). It carries numerous useful agronomic traits and constitutes a tertiary gene pool for wheat improvement (Fedak and Han 2005). To date, several bread wheat–Th. intermedium amphiploids have been obtained and characterized by means of genomic in situ hybridization (Chen et al. 2003; Fedak and Han 2005; Bao et al. 2009; Chang et al. 2010; Georgieva et al. 2011). However, there are few amphiploids reported from durum wheat and Th. intermedium. Here we report the development of two new durum wheat–Th. intermedium partial amphiploids with resistance to multiple fungal pathogens. In this investigation, we attempted to determine the chromosome composition and genomic origins of the alien chromosomes of two partial amphiploids by genomic in situ hybridization (GISH).

Material and methods

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Plant material

Two durum wheat–Th. intermedium partial amphiploid lines, 08-47-50 and 08-53-55, analyzed in this study, are BC1F6 derivatives. The 08-47-50 was produced by crossing durum wheat line DR88S062 as female parent with a Th. intermedium accession of unknown origin. The hybrid was backcrossed to another durum wheat cultivar DR1022. The 08-53-55 combination was generated from the cross between durum wheat DR1022 and Th. intermedium and then backcrossed to another durum wheat DR46. Other wheat cultivars Roblin, Sumai 3, Thatcher and Hoffman were used as checks in the present FHB, leaf rust and stem rust evaluations. Total genomic DNA from durum wheat cultivar DR46, Th. intermedium, Pseudoroegneria strigosa (M. Bieb.) Á. Löve (St genome) and Thinopyroum elongatum (Host) Á. Löve (E genome) was used as probes or blockers for GISH analyses.

Chromosome preparation

Seeds were germinated on moistened filter paper in Petri dishes. The actively growing roots were collected at lengths of 1–1.5 cm. The root tips were immersed in ice-water for about 24 h and fixed in ethanol-acetic acid (3:1) for about one week at room temperature and then stored in 70% (v/v) ethanol. After staining with 1% (w/v) aceto-carmine for at least 2 h, the root tips were squashed in 45% (v/v) acetic acid. For meiotic chromosome pre paration, young spikes at the meiotic metaphase I stage were fixed in 95% ethanol–chloroform–glacial acetic acid (6:3:1) at room temperature for 48 h, then maintained in 70% ethanol at 4°C. Anthers were stained and squashed in 1% acetocarmine.

Genomic in situ hybridization analysis

The prepared slides were frozen at –70°C for about four days, and then the cover slips were removed using a razor blade. Slides were then dehydrated in 70%, 95%, 100% ethanol for 5 min each and then air-dried at room temperature before use. Genomic DNA of Th. intermedium was extracted by a modified CTAB method and labeled with digoxigenin-11-dUTP using a nick translation mix (Roche, Germany) for probing. Sheared genomic DNA of durum wheat was used as blocking DNA.

Slide treatment, hybridization and signal detection of the fluorescence was carried out as described in the following procedure. Slides were first denatured in 70% deionized formamide at 75°C for 3 min and then dehydrated in an ethanol series (70%, 95% and 100%) for 5 min each. The hybridization mixture was prepared per slide in 15 μl, consisting of 7.5 μl deionized formamide, 100 ng digoxigenin genomic DNA, 0.5 μl 20×SSC, 3 μl 50% dextran sulphate, 7.5 μg salmon sperm DNA and 6–8 μg sheared blocking DNA. The hybridization mixture was denatured at 80°C for 10 min, immediately chilled on ice for 5–10 min, and then added onto the post-dehydrated slides for hybridization. After an overnight hybridization at 37°C, post-hybridization washes were performed in 2 × SSC at room temperature for 5 min, 2 × SSC at 42°C for 10 min and 1 × PBS for 5 min. The slides were incubated with 10 μg ml−1 anti-digoxigenin-rhodamine or strepavidin-fluroscein isothiocyanate (FITC) (Roche) in PBS buffer for 30 min at 37°C to detect digoxigin and/or biotin. The slides were then washed three times in 1 × PBS for 5 min each time. The chromosomes were finally counterstained with DAPI (5 μg ml−1) solution (Vectashield mounting media, Vector Laboratories, Inc.).

For multiple-color GISH analysis, total genomic DNAs from Pseudoroegneria strigosa (St) labeled with biotin-16-dUTP and Th. elongatum (Ee) labeled with digoxingenin-11-dUTP by the nick translation method were used as probes. Total genomic DNA of durum wheat was used for blocking. Digoxigenin and biotin were detected using anti-digoxingenin-rhodamine Fab fragments and streptavidin-fluroscein thiocyanate (FITC) (Roche), respectively. The chromosomes were finally counterstained with DAPI solution. The slides were visualized with a fluorescence Zeiss Axioplan 2 microscope equipped with the appropriate filters and the signal patterns were taken by CCD camera (Zeiss, Germany).

Evaluation of disease resistance

Three separate plants from a bulk source of BC1F6 seeds were used for screening. In each pot, three spikes at similar developmental stage per plant were inoculated for FHB resistance. At anthesis, one floret in the middle of each spike was injected with 10 μl of inoculum (50 000 spores ml−1) of a mixture of three F. graminearum isolates: DAOM178148, DAOM232369 and DAOM 212678 (Canadian Collection of Fungal Cultures, Agriculture and Agri-Food Canada, Ottawa, Canada). The inoculated plants were firstly misted for 48 h (15 s of misting every 15 min) and then grown at 25°C for FHB development. At 21 days after the initial inoculation, the number of infected spikelets per inoculated spike was scored. The percentage of symptomatic spikelets in an inoculated spike was calculated to measure type II resistance. Roblin was served as the susceptible check and Sumai 3 was used as a resistant check. The FHB evaluation was conducted in a greenhouse with a completely randomized design. The data were analyzed using one-way analysis of variance (Software package 16.0, SPSS). Individual differences among means were determined by Turkey’s test at a significant level of P <0.05.

The partial amphiploid lines of 08-47-50 and 08-53-55 were tested at the seedling stage against the Puccinia triticinia (Pt) pathotypes, 96-12-3 MBDS, 95-77-2 TJBJ, 95-74-2 MGBJ, 94-128-1 MBRJ, 06-1-1 TDBG and three mixtures of virulence phenotypes used to represent the genetic and virulence diversity of P. triticina found within Canada in each of three years (2005, 2006 and 2008). The Puccinia graminis Pers. f. sp. tritici (Pgt) pathotypes, race Ug99 (also designed TTKSK) and its variant TTKST were also used as the inoculum. Each isolate was developed from a single pustule and the purity of each isolate was tested by inoculating a set of standard host differential lines as described previously (McCallum and Seto-Goh 2005). To inoculate with each isolate or mixture, ten seedlings per line were planted in a clump and the clumps were evenly spaced in a fiber flat (25 × 15 cm). Spores were suspended in a light mineral oil (Bayol, Esso Canada, Toronto, ON), and sprayed onto seedlings at the 1–2 leaf stage. The plants were allowed to dry for one hour, and then incubated in a chamber at 20 ± 4°C with 100% relative humidity in the dark for 17 h. Plants were transferred to a greenhouse for symptom development at 20 ± 4°C with supplemental high-pressure sodium lights. The infection types were recorded as described by McIntosh et al. (1995), with some modification, at 14 days after inoculation. The infection types (IT) of both leaf rust and stem rust were: “0”= immune response, “;”= hypersensitive flecks, “1”= small uredinia with necrosis, “2”= medium sized uredinia with chlorosis or necrosis, “3”= medium sized uredinia without chlorosis or necrosis and “4”= abundant large uredinia without chlorosis or necrosis. Similarly “−” and “+”, respectively, explained slight variations in the expression of an IT.

Results

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Meiotic analysis of partial amphiploids

Chromosome configurations at metaphase I of PMCs were carried out for the two new partial amphiploids. The results showed that both partial amphiploid lines had a chromosome number of 2n = 42 (Fig. 1A–B). In the line 08-47-50, frequencies of univalents ranged from 0 to 4 after observation of 100 pollen mother cells, and no more than one trivalent occurred in other cells. The mean chromosome configuration at MI was 0.75I + 20.49II + 0.09 III. In the line 08-53-55, frequencies of univalents ranged from 0 to 4 and the bivalents ranged from 19 to 21. The mean chromosome configuration was 0.66I + 20.67II. These results of meiotic analysis confirmed that the two novel partial amphiploids were basically cytologically stable.

image

Figure 1A–B. Meiotic configuration at metaphase I. (A) 08-47-50, 2n = 42 = 21 II (rings), (B) 08-53-55, 2n = 42 = 18 II (rings) + 3 II (rods).

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GISH identification of partial amphiploids

By probing with digoxigenated total genomic DNA of Thinpyrum intermedium and blocking with genomic DNA of durum wheat, 14 Th. intermedium chromosomes and 28 durum wheat chromosomes were distinguished in both 08-47-50 and 08-53-55 (Fig. 2A). No translocation involving durum wheat and Th. intermedium chromosomes was observed. The multiple-color GISH technique was also carried out to examine the alien chromosome composition as well as possible inter-genomic interchanges by using genomic DNAs of P. strigosa (St) and Th. elongatum (Ee) as probes. In line 08-47-50, the GISH patterns from probing with St and Ee genomic DNAs revealed that six chromosomes were labeled over the entire length by a green fluorescence signal and therefore belonged to the St genome. Four chromosomes had red hybridization signals and were identified as Ee genome chromosomes. Two pairs of chromosomes had translocations involving the Ee and St genomes. One pair of chromosomes had green hybridization signals at its terminal region and the other chromosome region had red hybridization signals, indicating a terminal translocation. The other translocated chromosome pair had an intercalary translocation, in which the terminal region of the short arm and the entire long arm showed St genomic hybridization signals (Fig. 2B) with an E genome segment at an interstitial location.

image

Figure 2A–C. The GISH patterns of 08-47-50 and 08-53-55 lines. (A) Total genomic DNA of Th. intermedium was used for probing. (B) (08-47-50) and (C) (08-53-55): The St genome is visualized in green, the Ee genome in red, and the durum wheat chromosomes in blue or grey blue. The interstitial translocation chromosomes involving Ee and St genomes indicated with arrows and double arrows.

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In the line of 08-53-55, it was shown that four chromosomes were hybridized by the St genomic probe and ten translocated chromosomes involving Ee and St genomes were detected. Of the ten translocated chromosomes, eight chromosomes had St genomic hybridization signals at the terminal region of both arms. The remaining two translocated chromosomes were labeled by Ee hybridization signals at the centromeric region and short arm (Fig. 2C). Accordingly, the genomic constitution formula of 08- 47-50 was concluded to be 28DW + 6St + 4Ee+ 4Ee-St, and 08-53-55 had a genomic constitution of 28DW + 4St + 10Ee-St (DW 5 durum wheat chromosomes).

FHB symptom spread

Under greenhouse conditions, the fungal infection was restricted to the centrally inoculated spikelets in both partial amphiploids, and thus showing lower overall mean infection scores. The mean percentage of symp tomatic spikelets was 6.33% in 08-47-50 and 5.91% in 08-53-55, whereas the checks had 14.78% for Sumai 3 and 100% for Roblin (p = 0.05) (Table 1). Therefore, the FHB damage was significantly lower in both par tial amphiploids than in Roblin (100%) and Sumai 3 (14.78%).

Table 1.  Reactions to FHB and stem rust races TTKSK and TTKST for two durum wheat–Thinopyrum inter medium partial amphiploids.
 Stem rust pathotypes/infection type 
LineTTKSKTTKSTFHB severity (%)
  1. nt = not tested. Within the FHB severity column, values followed by different letters are significantly different at the P < 0.05 level according to Tukey’s multiple range test.

08-47-501;6.33c
08–53-55115.91c
Roblinntnt100a
Sumai 3ntnt14.78b
Hoffman33nt

Leaf rust and stem rust responses

Seedling rust response scores for both partial amphiploids 08-47-50 and 08-53-55 against two Pgt pathotypes and five Pt pathotypes and three mixtures of virulence Pt pathotypes collected in Canada in each of three years 2005, 2006 and 2008 are presented in Table 1 and 2.

Table 2.  Reactions to different leaf rust races for two durum wheat–Thinopyrum intermedium partial amphiploids.
 Leaf rust pathotypes/infection typea
LineMBRJMGBJTJBJTDBGMBDSEpidemic-05Epidemic-06Epidemic-08
  1. a0; = presence of slightly higher response than 0, 1−= presence of slightly lower response than 1, 1+= presence of slightly higher response than 1, 3−= presence of slightly lower response than 3, ;1−= presence of slightly higher response than ; and slightly lower response than 1. Scores of 0–2 are classified as resistant and 3–4 as susceptible reactions.

08–47-500;001−1−0;0;0;
08–53-55;1−;;1−1−1+;1−;1−;
Thatcher33−3−3−3−3−3−3−

08-47-50 exhibited infection type 1 and ; against TTKSK and TTKST, respectively, while 08-53-55 exhibited infection type 1 against the two Pgt pathotypes (Table 1). The leaf rust response to five Pt pathotypes and three mixtures of virulence Pt phenotypes in 08-47-50 ranged from infection type 0 to 1− (Table 2). 08-53-55 expressed infection type from ; to 1+. Thatcher was susceptible (infection type from 3− to 3+) to all five Pt pathotypes and three mixtures of Pt pathotypes. Figure 3 shows the leaf rust and stem rust infection types in 08-47-50, 08-53-55 and susceptible checks.

image

Figure 3. Seedling leaf rust and stem rust responses of partial amphiploids against Pt pathoype MBRJ (1 08-47-50, 2 08-53- 55 and 3 Thatcher) and Pgt pathotype TTKST (4 08-47-50 and 5 Hoffman)

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Discussion

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

Discovering novel and diverse sources of resistance is critical for retaining genetic variation for disease and pest resistance in wheat breeding programs, because deployment of only one or a few sources of resistance over large crop production areas poses a danger of resistance breakdown and disease epidemics. As an important perennial Triticeae species, Thimopyrum intermedium has frequently been used in bread wheat improvement as a donor of various disease resistance genes, in particular for those which to a large extent are lacking in bread wheat or durum wheat. To date, genes for various disease resistances have been transferred from Th. intermedium to bread wheat, such as Wsm1 conferring resistance to wheat streak mosaic virus (WSMV) (Friebe et al. 1991), Bdv2 (Zhang et al. 1999) and Bdv3 (Ohm et al. 2005) specifying resistance to barley yellow dwarf virus (BYDV), Pm40 (Luo et al. 2009) and Pm43 (He et al. 2009) resistance to powdery mildew, Lr38 (Friebe et al. 1992) resistance to leaf rust, and Sr44 (Friebe et al. 1996) resistance to stem rust. Resistance to FHB from Th. intermedium was also identified in derived wheat progenies (Oliver et al. 2005). FHB resistance was also detected in partial amphiploid obtained from a durum ×Th. distichum combination (Chen et al. 2001).

Development of partial amphiploids is an important first step by which to enhance wheat genetic diversity and transfer alien disease resistant genes into wheat. It is essential to know the exact genomic composition of the added alien chromosomes in the partial amphiploids. The genome constitution of Th. intermedium was determined to be EeEeSt (Liu and Wang 1993) or EeEbSt (Chen et al. 1998) with Ee (=J) and Eb (=Js) designating the closely related Th. elongatum and Th. bessarabicum genomes. Lately, new insights in the genome composition of Th. intermedium became available (Kishii et al. 2005). Recent studies indicate that the genomic constitution of Th. intermedium may be somewhat more complex as revealved by the existence of sequences from Th. caespitosum, Taeniatherum caput-medusae and Crithopsis delileana in its genome (Arterburn et al. 2011). The existence of these sequences may be responsible for some of the different GISH staining patterns obtained. This aspect obviously requires additional study. In the present study, using genomic probes of St and Ee genome simultaneously, the results not only provided detailed information on the precise genomic constitution of the partial amphiploids 08-47-50 and 08-53-55, but also revealed the chromosome structural variation and rearrangement involving Ee and St genomes.

The GISH results clearly demonstrated that the difference in genomic constitution between 08-47-50 and 08-53-55 was due to the different ratio (E-St) of alien chromosomes of Th. intermedium and the differences in translocated chromosomes. 08-47-50 contained six St genome chromosomes, four Ee genome chromosomes and two pairs of Ee-St translocated chromosomes plus twenty-eight durum wheat chromosomes. 08-53-55, in addition to the complete durum wheat genome, consisted of four chromosomes of the St genome, and five pairs of Ee-St translocated chromosomes. In terms of translocated chromosomes, different fragment sizes of Ee-St reciprocal translocations were detected, showing the fragment of Ee genome on the short arm of two St-chromosomes in 08-47-50 and the larger fragment of Ee genome involving the centromeric region on the two St-chromosomes in 08-53-55. In addition, two Ee-St terminal translocation chromosomes and two interstitial translocation chromosomes of Ee-St were further discerned in 08-47-50. Eight Ee-St terminal translocation chromosomes and two Ee-St interstitial translocation chromosomes were observed in 08-53-55. However, we did not observe any St-signal near the centromeric region using the St-genome probe, which is not consistent with the previous reports (Chen et al. 2003; Bao et al. 2009). This difference in results seems attributable to the polymorphism of St genome chromatin. Another reasonable explanation could be that the chromosome constitution of Th. intermedium varies greatly among and within accessions (Xu and Conner 1994).

Interstitial translocations were detected in partial amphiploid 08-47-50 in this study. Such translocations are rare in more conventional plant genomes and hybrids (Jiang et al. 1993), but have been reported in a number of partial amphiploids (Fedak et al. 2000; Fedak and Han 2005; Chang et al. 2010). Perhaps they occur more frequently in the genomes of complex polyploids where some of the genomes such as E and J are closely related, and are now being detected by multicolor GISH technology.

At metaphase I, the chromosomes pairing association of 08-47-50 was similar to that of 08-53-55 with high frequencies of bivalent and very low multivalent formation. In 08-47-50, most (about 70% of the 120 cells analyzed) cells formed 21 bivalents and only 0.75 unpaired chromosomes and 0.09 trivalents occurred per cell. While 08-53-55 had the expected 21 bivalents which occupied about 82% of the 120 cells analyzed. Only 0.66 univalents occurred per cell at metaphase I. These meiotic configurations indicated that the two novel partial amphiploids had a basic stability in cytology with a vigorous growth habit and high fertility. As described by Fedak et al. (2000), Thinopyrum-derived partial amphiploids normally have regular meiosis with high frequencies of bivalent configurations and low frequencies of multivalents. Their genomes should be largely balanced in terms of homoeologous chromosomes (Fedak and Han 2005). This is in contrast to partial amphiploids derived from a durum wheat and Th. distichium combination where progeny with 50 and 42 chromosomes were obtained with only the latter being stable.

In previous researches, the genes for resistance to WSMV, BYDV, rust and powdery mildew were not located on chromosomes of the St genome but on those of Ee (J) or Eb (Js) genomes as determined by C banding, GISH and molecular marker analyses (Kong et al. 2009; Li et al. 2005). In the present study, the fungal disease evaluation showed that 08-47-50 and 08-53-55 were resistant to FHB, leaf rust and stem rust. GISH revealed that 08-47-50 had six St chromosomes, four Ee chromosomes and four translocated chromosomes involving Ee and St chromosomes. While four St chromosomes and ten Ee-St translocated chromosomes were discerned in 08-53-55. Ee and St genome chromosomes could be associated with resistance to FHB since durum has no FHB resistance.

Fungal diseases are caused by a very dynamic group of plant pathogens. Both leaf rust and FHB annually cause epidemics in the world. A new stem rust pathotype Ug99 with serious virulence on the widely deployed resistance gene Sr31 was detected in Uganda in 1999 and has since mutated to two additional variants (Pretorius et al. 2000; Jin and Singh 2006; Jin et al. 2008). The genetic flexibility of these pathogens has lead breeders to respond with a constant search for new resistance genes and incorporating them into wheat genetic backgrounds. Our present study revealed that the two novel partial amphiploids harbour a variety of resistance genes to several major fungal diseases. It is expected that more genes for resistance against diseases can be discovered in Th. intermedium, especially the genes that rarely occur in bread wheat or durum wheat. We are currently making backcrosses to bread wheat and durum wheat in order to develop addition, substitution and translocation lines with resistance to FHB, leaf rust and stem rust.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References

This work was supported by the MOE-AAFC PhD Research Programme.

References

  1. Top of page
  2. Abstract
  3. Material and methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. References
  • Arterburn M., Kleinhofs A., Murray T. et al. 2011. Polymorphic nuclear gene sequences indicate a novel genome donor in the polyploid genus Thinopyrum. Hereditas 148: 827.
  • Ayliffe M., Singh R. and Lagudah E. 2008. Durable resistance to wheat rust needed. Curr. Opin. Plant Biol. 11: 187192.
  • Bai G. and Shaner G. 1994. Scab of wheat: prospects for control. Plant Dis. 78: 760766.
  • Bao Y., Li X., Liu S. et al. 2009. Molecular cytogenetic characterization of a new wheat–Thinopyrum intermedium partial amphiploid resistance to powdery mildew and stripe rust. Cytogenet. Genome Res. 126: 390395.
  • Chang Z. J., Zhang X. J., Yang Z. J. et al. 2010. Characterization of a partial wheat–Thinopyrum intermedium amphiploid and its reaction to fungal diseases of wheat. Hereditas 147: 304312.
  • Chen Q., Friebe B., Conner R. L. et al. 1998. Molecular cytogenetic characterization of Thinopyrum intermedium-derived wheat germplasm specifying resistance to wheat streak mosaic virus. Theor. Appl. Genet. 96: 17.
  • Chen Q., Eudes F., Conner R. L. et al. 2001. Molecular cytogenetic analysis of a durum wheat ×Thinopyrum distichum hybrid used as a new source of resistance to Fusarium head blight in the greenhouse. Plant Breed. 120: 375380.
  • Chen Q., Conner R. L., Sun S. C. et al. 2003. Molecular cytogenetic discrimination and reaction to wheat streak mosaic virus and the wheat curl mite in Zhong series of wheat–Thinopyrum intermedium partial amphiploids. Genome 46: 135145.
  • Ellneskog-Staam P. and Merker A. 2002. Chromosome composition, stability and fertility of alloploids between Triticum turgidum var. carthlicum and Thinopyrum junceiforme. Hereditas 136: 5965.
  • Fedak G. and Han F. 2005. Characterization of derivatives from wheat–Thinopyrum wide crossed. Cytogenet. Genome Res. 109: 360367.
  • Fedak G., Chen Q., Conner R. L. et al. 2000. Characterization of wheat–Thinopyrum partial amphiploids by meiotic ana lysis and genomic in situ hybridization. Genome 43: 712719.
  • Friebe B., Mukai Y., Dhaliwal H. S. et al. 1991. Identification of alien chromatin specifying resistance to wheat streak mosaic and greenbug in wheat germplasm by C-banidng and in situ hybridization. Theor. Appl. Genet. 81: 381389.
  • Friebe B., Zeller F. J., Mukai Y. et al. 1992. Characterization of rust-resistant wheat–Agropyron intermedium derivatives by C-banding, in situ hybridization and isozyme analysis. Theor. Appl. Genet. 83: 775782.
  • Friebe B., Jiang J., Raupp W. J. et al. 1996. Characterization of wheat-alien translocation conferring resistance to diseases and pests: current status. Euphytica 91: 5987.
  • Georgieva M., Sepsi A., Tyankova N. et al. 2011. Molecular cytogenetic characterization of two high protein wheat–Thinopyrum intermedium partial amphiploids. J. Appl. Genet. 52: 269277.
  • He R. L., Chang Z. J., Yang Z. J. et al. 2009. Inheritance and mapping of powdery mildew resistance gene Pm43 introgression from Thinopyrum intermeidum into wheat. Theor. Appl. Genet. 118: 11731180.
  • Jiang J., Chen P., Friebe B. et al. 1993. Alloplasmic wheat –Elymus ciliaris chromosome addition lines. Genome 36: 327333.
  • Jin Y. and Singh R. P. 2006. Resistance in US wheat to recent eastern African isolates of Puccinia graminis f. sp. tritici with virulence to resistance gene Sr31. Plant Dis. 90: 476480.
  • Jin Y., Szabo L. J., Pretorious Z. et al. 2008. Detection of virulence to resistance gene Sr24 within race TTKS of Puccinia graminis f. sp. tritici. Plant Dis. 92: 923926.
  • Kishii M., Wang R. R.-C. and Tsujimoto H. 2005. GISH analysis revealed new aspect of genomic constitution of Thinopyrum intermedium. Czech J. Genet. Plant Breed. 41: 9295.
  • Kong L., Anderson J. M. and Ohm W. 2009. Segregation distortion in common wheat of a segment of Thinopyrum intermedium chromosome 7E carrying Bdv3 and develop ment of a Bdv3 marker. Plant Breed. 128: 591597.
  • Li H. J., Arberburn M., Jones S. S. et al. 2005. Murray TD: resistance to eyepot of wheat, caused by Tapesia yallundae, derived from Thinopyrum intermedium homoelogous group 4 chromosomes. Theor. Appl. Genet. 111: 932940.
  • Liu Z. W. and Wang R. R.-C. 1993. Genome analysis of Elytrigia caespitose, Lophopyrum nodosum, Pseudoroegneria geneiculata ssp. scythica and Thinopyrum intermedium (Triticeae: Gramineae). Genome 36: 102111.
  • Luo P. G., Luo H. Y., Chang Z. J. et al. 2009. Characterization and chromosomal location of Pm40 in common wheat: a new gene for resistance to powdery mildew derived from Elytrigia intermedium. Theor. Appl. Genet. 118: 10591064.
  • McCallum B. and Seto-Goh P. 2005. Physiological specialization of wheat leaf rust (Puccinia triticina) in Canada in 2002. – Can. J. Plant Pathol. 27: 9095.
  • McIntosh R. A., Wellings C. R. and Park R. F. 1995. Wheat rusts: an atlas of resistance genes. – Kluwer Press.
  • Ohm H. W., Anderson J. M., Sharma H. C. et al. 2005. Registration of yellow dwarf viruses resistant wheat germplasm line P961341. – Crop Sci. 45: 805806.
  • Oliver R. E., Cai X., Xu S. S. et al. 2005. Wheat-alien species derivatives: a novel source of resistance to Fusarium head blight in wheat. Crop Sci. 45: 13531360.
  • Pretorius Z. A., Singh R. P., Wagorie W. W. et al. 2000. Dectection of virulence to wheat stem rust resistance gene Sr31 in Puccinia graminis f. sp. tritici in Uganda. Plant Dis. 84: 203.
  • Stack R. W. 2003. History of Fusarium head blight with emphasis on North America. – In: Leonard K. J. and Bushnell W. R. (eds), Fusarium head blight of wheat and barley. APS Press, St Paul, MN, pp. 134.
  • Stokstad E. 2007. Deadly wheat fungus threatens world’s breadbasket. Science 315: 17861787.
  • Xu J. and Conner R. L. 1994. Intravarietal variation in satellites and C-banded chromosomes of Agropyron intermedium ssp. trichophorum cv. Greenleaf. Genome 37: 305310.
  • Zhang Z. Y., Xin Z., Ma Y. Z. et al. 1999. Mapping of a BYDV resistance gene from Thinopyrum intermedium in wheat background by molecular markers. Sci. China Ser. C 42: 663668.