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Registration of KS93WGRC27 wheat streak mosaic virus-resistant T4DL·4Ai#2S wheat germplasm

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... The chromosome arm of 4Ai#2 in these lines originated from a wheat-Th. intermedium T4DLAE4Ai#2S translocation line KS93WGRC27, which was derived from CI 17884 (Gill et al. 1995). The spring wheat cultivar Chinese Spring and the winter wheat cultivar Hill 81 were used as susceptible checks. ...
... Introgression of multiple sources of alien chromosomes can complicate the genomic compositions of wheat making them unsuitable for commercial use. Wheat lines that carry only the short arm 4Ai#2S (=4J s S) conferring resistance to WSMV have been developed (Gill et al. 1995;Table 3 PCR amplification of Thinopyrum chromatin using primers 2P1 and 2P2 specific for a repetitive DNA fragment, pLeUCD2, originating from Thinopyrum elongatum and reaction to Tapesia yallundae wheat-Th. intermedium lines with or without chromosome arm 4Ai#2 Line Pedigree PCR using primers specific for Symptom severity of eyespot was rated visually on a 1 to 4 scale, where 1 = no lesion, and 4 = a lesion covering the entire first leaf sheath and two-thirds of the second sheath. ...
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Thinopyrum intermedium was identified previously as resistant to Tapesia yallundae, cause of eyespot of wheat. Using GUS-transformed isolates of T. yallundae as inoculum, we determined that wheat lines carrying Th. intermedium chromosome 4 Ai#2 or the short arm of chromosome 4 Ai#2 were as resistant to the pathogen as the eyespot-resistant wheat- Th. ponticum chromosome substitution line SS 767 (PI 611939) and winter wheat cultivar Madsen, which carries gene Pch 1 for eyespot resistance. Chromosome 4 E from Th. elongatum and chromosome 4 J from Th. bessarabicum did not confer resistance to T. yallundae. Genome-specific PCR primers confirmed the presence of Thinopyrum chromatin in these wheat- Thinopyrum lines. Genomic in situ hybridization using an St genomic probe from Pseudoroegneria strigosa demonstrated that chromosome 4 Ai#2 belongs to the J(s) genome of Thinopyrum. The eyespot resistance in the wheat- Th. intermedium lines is thus controlled by the short arm of this J(s) chromosome. This is the first report of resistance to T. yallundae controlled by a J(s) genome chromosome of Th. intermedium.
... intermedium lines were also screened for their resistance to WSMV and the WCM. Lines A29-13-3 (Wang and Zhang 1996), KS93WGRC27 ( Gill et al. 1995), and CI 15092 ( Wells et al. 1973) were chromosome translocation or substitution lines, which carry the gene Wsm1 for resistance to WSMV. Line 54-41-14-5-5 was developed from a cross between wheat and Agrotana ( Chen et al. 1999). ...
... The WSMV resistance of other partial amphiploid lines, such as Agrotana, ORRPX, OK7211542, TAF46, and Zhong 4 was confirmed by their low ELISA values versus the high values for Chinese Spring. The lines KS93WGRC27, A29-13-3, and CI 15092, which possess the gene Wsm1 that confers WSMV resistance ( Wells et al. 1973;Gill et al. 1995;Wang and Zhang 1996), did not show systemic WSM symptoms at any time during the investigation. ELISA values in these lines were as low as that in the non-inoculated Chinese Spring check. ...
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Wheat streak mosaic virus (WSMV), vectored by the wheat curl mite (WCM),Aceria tosichella Keifer, is one of the most destructive viral diseases of wheat found in many wheat producing areas of the world. Host resistance is the most effective method for controlling this disease and its vector. Symptomatological analysis and enzyme-linked immunosorbent assay (ELISA) were used to characterize WSMV-resistance in wheat-alien partial amphiploid lines and their derivatives. The results showed that most of partial amphiploids derived fromThinopyrum ponticum andTh. intermedium were free of systemic symptoms with very low ELISA readings that were similar to that of the non-inoculated Chinese Spring control. While the partial amphiploid lines 693 and PWM706 were identified as new genetic resources of resistance to WSMV. The present study demonstrated that both symptomatological and ELISA methods efficiently assessed WSMV-resistance in the wheat-alien hybrids and systemic symptom incidence and ELISA absorbance readings were highly correlated (r 2 = 0.8658–0.9323) over time following inoculation. The ELISA results also indicated that the virus did not buildup in the plant tissues of these virus-resistant partial amphiploids. Similar results were observed in chromosome translocation and substitution lines that have the geneWsm1 conferring WSMV resistance. However, the lines containing the geneWsm1 and all the partial amphiploid lines, except Agrotana, were susceptible to the WCM. One line derived from a cross of wheat and Agrotana, was effective in controlling the spread of WSMV and was highly resistant to the WCM. Another line and an accession ofTriticum dicoccoides (Koern.) Schweinf. were highly susceptible to WSMV and WCM. Early disease development was delayed in a new hard red winter cultivar McClintock. The partial WSMV-resistance of McClintock was demonstrated by initially low ELISA readings, and a lower percentage of infected plants than other WSMV-susceptible wheat. The use of the identified promising sources of resistance to WSMV and the WCM in wheat breeding is discussed.
... An improved germplasm line WGRC27 containing the T4DL . 4Ai#2S translocation was released (Gill et al. 1995). WGRC27 has been widely used in breeding, but no cultivars have been released because of an adverse effect on yield potential. ...
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Sears (1956) pioneered plant chromosome engineering 50 years ago by directed transfer of a leaf rust resistance gene from an alien chromosome to a wheat chromosome using X-ray irradiation and an elegant cytogenetic scheme. Since then many other protocols have been reported, but the one dealing with induced homoeologous pairing and recombination is the most powerful, and has been extensively used in wheat. Here, we briefly review the current status of homoeologous recombination-based chromosome engineering research in plants with a focus on wheat, and demonstrate that integrated use of cytogenetic stocks and molecular resources can enhance the efficiency and precision of homoeologus-based chromosome engineering. We report the results of an experiment on homoeologous recombination-based transfer of virus resistance from an alien chromosome to a wheat chromosome, its characterization, and the prospects for further engineering by a second round of recombination. A proposal is presented for genome-wide, homoeologous recombination-based engineering for efficient mining of gene pools of wild relatives for crop improvement.
... Wheat varieties with resistance to the wheat curl mite have been developed; however, mite-resistant strains have developed and compromised their effectiveness (Harvey et al. , 1999. WSMV resistance has been identified and transferred into wheat (Wells et al. 1973(Wells et al. , 1982Friebe et al. 1991;Gill et al. 1995); however, few virusresistant varieties have been developed. 'Mace' was the first commercial variety released with resistance conferred by the wsm1 gene (Graybosch et al. 2009). ...
Article
Wheat is an important food grain worldwide, and it is the primary dryland crop in the western Great Plains. A complex of three viruses (Wheat streak mosaic, Wheat mosaic, and Triticum mosaic viruses) is a common cause of loss in winter wheat production in the Great Plains. All these viruses are transmitted by the wheat curl mite (Aceria tosichella Keifer). Once these viruses are established, there are no curative actions; therefore, prevention is the key to successful management. A study was designed to evaluate preventative management tactics (planting date, resistant varieties) for reducing the impact from this virus complex. The main plot treatments were three planting dates, and split-plot treatments were three wheat varieties. Varieties were planted at three different times during the fall to simulate early, recommended, and late planting dates. The varieties evaluated in this study were Mace (virus resistant), Millennium (mild tolerance), and Tomahawk (susceptible). Measurements of virus symptomology and yield were used to determine virus impact. Results consistently showed that the resistant Mace yielded more than Millennium or Tomahawk under virus pressure. In some years, delayed planting improved the yields for all varieties, regardless of their background; however, under the most severe virus pressure the combination of both management strategies was not sufficient to provide practi- cal control of this complex. These results illustrate the importance of using a combination of management tac- tics for this complex, but also reinforce the importance for producers to use additional management strategies (e.g., control preharvest volunteer wheat) to manage this complex.
... Agatha Sear transfer Sears transfer Knott, 1968Sears, 1973, 1977Sears, 1973, 1977Friebe et al., 1994 Th. ponticum T6AS·6AL-6Ae#1L 6A-6Ae#1L Friebe et al., 1994Knott, 1961 Sr43 Wells et al., 1982Gill et al., 1995Friebe et al., 1991 Th. ponticum T6DL·6Ae#2S T5BL·6Ae#2S T6AL·6Ae#2S Whelan and Hart, 1989Whelan and Hart, 1989Whelan and Lukow, 1990 Teewon (Sebesta et al., 1995a). Wheat cultivar Amigo carrying Lr24 was derived from Teewon (Sebesta et al., 1995b). ...
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Thinopyrum ponticum and Th. intermedium provide superior resistance against various diseases in wheat (Ttricum aestivum). Because of their readily crossing with wheat, many genes for disease resistance have been introduced from the wheatgrasses into wheat. Genes for resistance to leaf rust, stem rust, powdery mildew, Barley yellow dwarf virus, Wheat streak mosaic virus, and its vector, the wheat curl mite, have been transferred into wheat by producing chromosome translocations. These genes offer an opportunity to improve resistance of wheat to the diseases; some of them have been extensively used in protecting wheat from damage of the diseases. Moreover, new resistance to diseases is continuously detected in the progenies of wheat-Thinopyrum derivatives. The present article summaries characterization and application of the genes for fungal and viral disease-resistance derived from Th. ponticum and Th. intermedium.
... intermedium chromosome 4Ai#2, resulting in the translocation chromosome T4DL·4Ai#2S. Wsm1 was shown to belong to the J s genome of Th. intermedium (Chen et al., 1998b) and was transferred to the Kansas winter wheat cultivar Karl, and a germplasm was released as KS93WGRC27 (Gill et al., 1995). Wsm1 is temperature sensitive and confers immunity to WSMV at low temperatures around 18°C, whereas at higher temperatures around 24°C, the resistance is ineff ective (Seifers et al., 1995). ...
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W heat streak mosaic caused by Wheat streak mosaic virus (WSMV) and transmitted by the wheat curl mite (Aceria tosichella Kiefer), is a devastating virus disease of common wheat (Triticum aestivum L., 2n = 6x = 42, ABD) in the Great Plains of the United States and Canada and in most spring and winter wheat-producing areas worldwide. Yield losses of wheat infected with WSMV averaged 2.5% (Sim et al., 1988; Christian and Wil-lis, 1993; Bockus et al., 2001), but severe infection can result in complete crop loss (McNeil et al., 1996). High levels of resistance to WSMV are not present in closely related species belonging to the primary and secondary gene pool of wheat. Only some perennial species, including Thinopyrum intermedium (Host) Bark-worth and Dewey (2n = 6x = 42, JJ s S) and Th. ponticum (Podp.) Barkworth and Dewey (2n = 10x = 70, JJJJ s J s), have been reported to have resistance to either WSMV or its vector (McKinney and Sando, 1951; Martin et al., 1976; Stoddard et al., 1987a,b; Friebe et ABSTRACT To date, only one gene conferring resistance to Wheat streak mosaic virus (WSMV) designated as Wsm1 was transferred from Thinopyrum inter-medium (Host) Barkworth and Dewey to wheat (Triticum aestivum L.) in the form of a compen-sating Robertsonian translocation T4DL·4J s S. Wsm1 confers high levels of resistance to WSMV under fi eld conditions; however, in certain genetic backgrounds and environments, the presence of the T4DL·4J s S translocation reduces agro-nomic performance. The objective of this study was to shorten the Th. intermedium segment in the T4DL·4J s S translocation. We recovered one proximal (rec36) and four distal (rec45, rec64, rec87, rec213) primary recombinants. Genomic in situ hybridization and molecular marker analy-ses determined the size of the Th. intermedium segments in the distal recombinants to be about 20% of the 4DS-4J s S arm. All primary recombi-nant stocks, together with appropriate controls, were evaluated for their resistance to WSMV and Triticum mosaic virus (TriMV) in greenhouse tests. Whereas the distal recombinants rec45, rec64, rec87, and rec213 were resistant to both WSMV and TriMV at low temperatures of 18°C, the proximal recombinant rec36 reacted suscep-tible, which mapped the Wsm1 gene to the dis-tal 20% of the 4DS-4J s S arm. We successfully shortened the Th. intermedium segment while still retaining the Wsm1 gene. The T4DL·4DS-4J s S recombinant chromosome of the rec213 stock was transferred to adapted Kansas hard red winter wheat cultivars.
... Useful sources of resistance have been incorporated into wheat cultivars adapted for Kansas to wheat streak mosaic (12,16), the foliar diseases caused by the Septoria complex (Septoria tritici leaf blotch [8,9] and Stagonospora nodorum leaf blotch [8] [ Table 3]), and scab (7). Because of the highly erratic occurrence of these diseases and the relatively short time that resistant cultivars have been available, the effect of resistance is till unclear. ...
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the development, release, and adoption of wheat cultivars with resistance to important wheat diseases. As a result of the annual disease survey and estimation of losses, the impact that resistant cultivars had on disease losses could be quantified. This paper de- scribes the use of genetic resistance in wheat for control of diseases and related yield effects in Kansas during the past 25 to 30
... What curl mite is a vector for WSMV. 'Mace' and KS93WGRC27 are resistant to WSMV and contain Wsm1 that was transferred from KS91H184, a derivative of a translocation line, CI 17884 (Gill et al., 1995; genes for resistance to RWA and GB were not screened on SRPN lines; however, evaluation of resistance of the lines was done with artificial infestation in standard greenhouse screening tests (SRPN, 2013). Among the 174 SRPN lines tested during the five year period, only six lines have resistance to RWA, three lines are resistant to GB, and 13 lines are resistant to Hf. ...
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Biotic stresses including diseases (leaf, stem and stripe rusts), arthropods (greenbug [GB], Hessian fly [Hf], Russian wheat aphid [RWA], and wheat curl mite [WCM]) and their transmitted viral diseases significantly affect grain yield and end-use quality of hard winter wheat (Triticum aestivum L.) in the U.S. Great Plains. Many genes or quantitative trait loci (QTL) have been identified for seedling or adult-plant resistance to these stresses. Molecular markers for these genes or QTL have been identified using mapping or cloning. This study summarizes the markers associated with various effective genes, including genes or QTL conferring resistances to arthropods, such as GB (7), RWA (4), Hf (9), and WCM (4) and diseases including leaf, stem and stripe rusts (26) and Wheat streak mosaic virus (WSMV; 2); genes or QTL for end-use quality traits such as high (3) and low (13) molecular weight glutenin subunits, gliadin (3), polyphenol oxidase (2), granule-bound starch synthase (3), puroindoline (2), and preharvesting sprouting (1); genes on wheat–rye (Secale cereale L.) chromosomal translocations of 1AL.1RS and 1BL.1RS; and genes controlling plant height (12), photoperiod sensitivity (1), and vernalization (2). A subset of the markers was validated using a set of diverse wheat lines developed by breeding programs in the Great Plains. These analyses showed that most markers are diagnostic in only limited genetic backgrounds. However, some markers developed from the gene sequences or alien fragments are highly diagnostic across various backgrounds, such as those markers linked to Rht-B1, Rht-D1, Ppd-D1, Glu-D1, Glu-A1, and 1AL.1RS. Knowledge of both genotype and phenotype of advanced breeding lines could help breeders to select the optimal parents to integrate various genes into new cultivars and increase the efficiency of wheat breeding.
... The Wsm1 gene donor was a hard red winter wheat line 'KS93WGRC27' (PI 583794) that carries the gene on an Agropyron intermedium (Host) P. Beauv. segment translocated on wheat chromosome 4DS (Friebe et al. 1991;Gill et al. 1995). This line was backcrossed five times to each of the hard red winter wheat cultivars: 'Wahoo' (Baenziger et al. 2002, PI 619098), 'Wesley' (Peterson et al. 2001, PI 605742,), 'Alliance' (Baenziger et al. 1995, PI 573096), 'Millennium' (Baenziger et al. 2001, PI 613099), 'Goodstreak' (Baenziger et al. 2004a, PI 632434) and 'Harry' (Baenziger et al. 2004b, PI 632435). ...
... What curl mite is a vector for WSMV. 'Mace' and KS93WGRC27 are resistant to WSMV and contain Wsm1 that was transferred from KS91H184, a derivative of a translocation line, CI 17884 (Gill et al., 1995; genes for resistance to RWA and GB were not screened on SRPN lines; however, evaluation of resistance of the lines was done with artificial infestation in standard greenhouse screening tests (SRPN, 2013). Among the 174 SRPN lines tested during the five year period, only six lines have resistance to RWA, three lines are resistant to GB, and 13 lines are resistant to Hf. ...
Conference Paper
Biotic stresses including diseases [leaf, stem and stripe rusts, and wheat streak mosaic virus (WSMV)] and insects [greenbug (GB), Hessian fly (Hf), Russian wheat aphid (RWA) and wheat curl mite (WCM)] significantly affect grain yield and end-use quality of hard winter wheat (HWW, Triticum aestivum L.) in the U.S. Great Plains. Many genes or quantitative traits loci (QTL) have been identified for seedling or adult plant resistance to these stresses. Molecular markers for these genes or QTL have been identified using mapping or cloning. This study summarizes the markers associated with various genes including genes or QTL conferring resistances to insects, such as GB (7), RWA (4), Hf (9), and WCM (4) and diseases including leaf, stem and stripe rusts (26) and WSMV (2); genes or QTL for end-use quality traits such as high (3) and low (13) molecular weight glutenin subunits, gliadin (3), polyphenol oxidase (2), granule-bound starch synthase (3), puroindoline (2), and pre-harvesting sprouting (1); genes on rye translocations with 1AL and 1BL; and genes associated with plant height (12) and photoperiod sensitivity (1). A subset of the markers was validated using a set of diverse wheat lines developed by breeding programs in the Great Plains. These analyses showed that most markers are diagnostic in only limited genetic backgrounds. However, some markers developed from the gene sequences or alien fragments are highly diagnostic across various backgrounds, such as Rht-B1, Rht-D1, Ppd-D1, Glu-D1, Glu-A1, and 1AL.1RS. Knowledge of both genotype and phenotype of advanced breeding lines could help breeders to select right parents to integrate various genes into new cultivars and increase the efficiency of wheat breeding.
... (i) fungal and viral resistance genes/QTL-Qfhs.jic-4D, Lr22, Lr67, Yr28, Wsm1, Wss1 [54][55][56][57][58][59]; (ii) aluminum or salt tolerance genes/QTLs -Alt2, Kna1 [60,61]; (iii) adaptation, flowering and yield-related genes/QTLs -Vrn2, Rht1, QSpn.fcu-4D [17,62,63,66,67], and (iv) quality-related genes -Lpx1 [68,69]. ...
Conference Paper
Sequencing wheat genome has always been viewed as a complex task because of its large size,ahigh repetitive DNA content and polyploidy. Several of previously mentioned constrains (largesize, polyploidy) can be overcome by flow sorting of individual chromosomes followed by shotgun-sequencing using next generation sequencing (NGS) technologies, and thus the IWGSC hasembraced this strategy. In this study we used 4D flow-sorted chromosome arms (obtained from cv Chinese Spring) toperform shotgun sequencing with a Roche 454 NGS platform producing sequence data equivalentto a 3.6x-chromosome coverage on single reads, plus 3kb paired end reads to overcome theproblem of repetitive regions during assembly. In order to reach a reliable and preliminary de novoassembly, short reads are being analyzed using different algorithms, strategies and parameters.The use of rapid alignment tools allow the identification of common (ie. emerging on variousassemblies) and trustable (emerging as more trustworthy variants when comparing differentassemblies) segments which have been in turn put through various validation steps. Multiple sources of evidence like EST collections, genetically mapped markers and gene contentsfor 4D chromosome where used to classify and assess both quality and completion of theassembly, pursuing the final goal of having additional metrics based on content,beyond contiglength and assembly coverage. The methodology of wheat chromosome assembly validationimplemented here, allows the integration of additional genomic information to help on gettingboth a measure of goodness and a strategy to improve short read assembly for plant genomes.
... (i) fungal and viral resistance genes/QTL-Qfhs.jic-4D, Lr22, Lr67, Yr28, Wsm1, Wss1 [54][55][56][57][58][59]; (ii) aluminum or salt tolerance genes/QTLs -Alt2, Kna1 [60,61]; (iii) adaptation, flowering and yield-related genes/QTLs -Vrn2, Rht1, QSpn.fcu-4D [17,62,63,66,67], and (iv) quality-related genes -Lpx1 [68,69]. ...
Article
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Survey sequencing of the bread wheat (Triticum aestivum L.) genome (AABBDD) has been approached through different strategies delivering important information. However, the current wheat sequence knowledge is not complete. The aim of our study is to provide different and complementary set of data for chromosome 4D. A survey sequence was obtained by pyrosequencing of flow-sorted 4DS (7.2×) and 4DL (4.1×) arms. Single ends (SE) and long mate pairs (LMP) reads were assembled into contigs (223Mb) and scaffolds (65Mb) that were aligned to Aegilops tauschii draft genome (DD), anchoring 34Mb to chromosome 4. Scaffolds annotation rendered 822 gene models. A virtual gene order comprising 1973 wheat orthologous gene loci and 381 wheat gene models was built. This order was largely consistent with the scaffold order determined based on a published high density map from the Ae. tauschii chromosome 4, using bin-mapped 4D ESTs as a common reference. The virtual order showed a higher collinearity with homeologous 4B compared to 4A. Additionally, a virtual map was constructed and ∼5700 genes (∼2200 on 4DS and ∼3500 on 4DL) predicted. The sequence and virtual order obtained here using the 454 platform were compared with the Illumina one used by the IWGSC, giving complementary information. Copyright © 2014 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.
... The donor of the Wsm1 gene was a hard red winter wheat line KS93WGRC27 (PI 583794) that carries the gene on a segment from Agropyron intermedium (Host) P. Beauv. translocated onto wheat chromosome 4DS (Friebe et al., 1991;Gill et al., 1995). With an objective to reduce the linkage drag, Friebe et al. (2009) were able to recover distal recombinants with 20% of the 4DS-4J s S arm (donor segment). ...
Article
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Seven winter wheat (Triticum aestivum L.) germplasm lines carrying the Wsm1 gene conferring resistance to Wheat streak mosaic virus (WSMV)-Alliance-Wsm1 (Reg. No. GP-858, PI 653710), Arrowsmith-Wsm1 (Reg. No. GP-859, PI 653711), Goodstreak-Wsm1 (Reg. No. GP-860, PI 653712), Harry-Wsm1 (Reg. No. GP-861, PI 653713), Millennium-Wsm1 (Reg. No. GP-862, PI 653714), Wahoo-Wsm1 (Reg. No. GP-863, PI 653715), and Wesley-Wsm1 (Reg. No. GP-864, PI 653716)-were codeveloped by Washington State University, Pullman, WA; the University of Nebraska, Lincoln, NE; and the USDA-ARS. These seven different winter wheat cultivars were selected to provide more sources of effective resistance to WSMV in winter wheat cultivars of Nebraska and adjoining states. Resistance to WSMV is conferred by the Wsm1 gene, which was translocated from Thinopyrum intermedium (Host) Barkworth & D.R. Dewey [Agropyron intermedium (Horst.) Beauv.] into wheat. The STSJ15 marker was used to select for the gene in the backcross progeny until the BC 4F 1 generation. In BC 4F 2 generation, screening for disease resistance was done using the Sidney 81 isolate of WSMV, along with the recurrent parents. Lines showing high levels of resistance to WSMV were further selected for seed increase and field evaluation. These lines may serve as a winter wheat source of WSMV resistance and may be used for gene pyramiding and for studying the effect of the Wsm1 gene in different backgrounds.
... intermedium Robertsonian translocation T4DL·4Ai#2S . T4DL Thinopyrum 4Ai#2S was transferred into the Kansas winter wheat cultivar Karl and the germplasm KS93WGRC27 was released (Gill et al. 1995). Wsm1 was later shown to be located on a J s -genome chromosome and, thus, the translocation chromosome was re-designated as T4DL·4J s S (Chen et al. 1999;Friebe et al. 2009). ...
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Key message: Here, we report the production of a wheat- Thinopyrum intermedium recombinant stock conferring resistance to wheat streak mosaic virus and Triticum mosaic virus. Wheat streak mosaic caused by the wheat streak mosaic virus (WSMV) is an important disease of bread wheat (Triticum aestivum) worldwide. To date, only three genes conferring resistance to WSMV have been named and two, Wsm1 and Wsm3, were derived from the distantly related wild relative Thinopyrum intermedium. Wsm3 is only available in the form of a compensating wheat-Th. intermedium whole-arm Robertsonian translocation T7BS·7S#3L. Whole-arm alien transfers usually suffer from linkage drag, which prevents their use in cultivar improvement. Here, we report ph1b-induced homoeologous recombination to shorten the Th. intermedium segment and recover a recombinant chromosome consisting of the short arm of wheat chromosome 7B, part of the long arm of 7B, and the distal 43% of the long arm derived from the Th. intermedium chromosome arm 7S#3L. The recombinant chromosome T7BS·7BL-7S#3L confers resistance to WSMV at 18 and 24 °C and also confers resistance to Triticum mosaic virus, but only at 18 °C. Wsm3 is the only gene conferring resistance to WSMV at a high temperature level of 24 °C. We also developed a user-friendly molecular marker that will allow to monitor the transfer of Wsm3 in breeding programs. Wsm3 is presently being transferred to adapted hard red winter wheat cultivars and can be used directly in wheat improvement.
... To date, three WSMV resistance genes, Wsm1, Wsm2, and Wsm3, have been identified. Both Wsm1 and Wsm3 were found in a wild relative, Thinopyrum intermedium (Host) Barkworth & D.R. Dewey, and they have been introduced into the wheat genome through translocation (Gill et al., 1995;Triebe et al., 1991). However, alien translocation often results in yield penalty due to the incorporation of non-adapted genes. ...
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Wheat streak mosaic virus (WSMV) causes streak mosaic disease in wheat ( Triticum aestivum L.) and has been an important constraint limiting wheat production in many regions around the world. Wsm2 is the only resistance gene discovered in wheat genome and has been located in a short genomic region of its chromosome 3B. However, the sequence nature and the biological function of Wsm2 remain unknown due to the difficulty of genetic manipulation in wheat. In this study, we tested WSMV infectivity among wheat and its two closely related grass species, rice ( Oryza sativa ) and Brachypodium distachyon . Based on the phenotypic result and previous genomic studies, we developed a novel bioinformatics pipeline for interpreting a potential biological function of Wsm2 and its ancestor locus in wheat. In the WSMV resistance tests, we found that rice has a WMSV resistance gene while Brachypodium does not, which allowed us to hypothesize the presence of a Wsm2 ortholog in rice. Our OrthoMCL analysis of protein coding genes on wheat chromosome 3B and its syntenic chromosomes in rice and Brachypodium discovered 4,035 OrthoMCL groups as preliminary candidates of Wsm2 orthologs. Given that Wsm2 is likely duplicated through an intrachromosomal illegitimate recombination and that Wsm2 is dominant, we inferred that this new WSMV-resistance gene acquired an activation domain, lost an inhibition domain, or gained high expression compared to its ancestor locus. Through comparison, we identified that 67, 16, and 10 out of 4,035 OrthoMCL orthologous groups contain a rice member with 25% shorter or longer in length, or 10 fold more expression, respectively, than those from wheat and Brachypodium. Taken together, we predicted a total of 93 good candidates for a Wsm2 ancestor locus. All of these 93 candidates are not tightly linked with Wsm2 , indicative of the role of illegitimate recombination in the birth of Wsm2 . Further sequence analysis suggests that the protein products of Wsm2 may combat WSMV disease through a molecular mechanism involving protein degradation and/or membrane trafficking. The 93 putative Wsm2 ancestor loci discovered in this study could serve as good candidates for future genetic isolation of the true Wsm2 locus.
... Two different types of resistance or tolerance to this disease have been described, one linked to the virus and the other to the vector. Genes conferring resistance to the virus, Wsm1 (Friebe et al. 1991;Gill et al. 1995), Wsm2 (Haley et al. 2002) and Wsm3 (Friebe et al. 2011), and to the vector, Cmc1 (ThomaS and Conner 1986), Cmc2 (Whelan and Hart 1988), Cmc3 and Cmc4 (Malik et al. 2003), were described. The genes Wsm1, Wsm2 and Wsm3 are thermo-sensitive, also known as TSR (temperature-sensitive resistance), since they lose effectiveness at high temperatures (between 24 and 27°C) (Seifers et al. 1995(Seifers et al. , 2007(Seifers et al. , 2013. ...
Article
Wheat streak mosaic virus (WSMV) is an emerging virus in South America that threatens cereal production. Genetic resistance is used in other regions as an effective strategy for management of this disease. The susceptibility of Argentine and Brazilian wheat cultivars to two WSMV isolates was evaluated. WSMV Argentinian isolates were evaluated following transmission with the mite vector Aceria tosichella under field and greenhouse conditions. Symptom severity and WSMV accumulation analyzed by DAS-ELISA in inoculated plants of 40 cultivars showed differential susceptibility levels, depending of the WSMV isolate. Nine cultivars including eight from Brazil and KS93WGR27/ProINRA Super from Argentina were tolerant to or uninfected with WSMV isolate GM-2009 under both conditions but susceptible to isolate MJ-2010. In contrast, the American cultivar MACE was resistant against the two Argentinian WSMV isolates.
Chapter
Rice is the world’s most important food crop with a total production around 600 million ton occupying 11% of the world’s total arable land; it supplies 2,808 calories/person/day, which represents 21% of the total calorie supply. It is source of income for more than 100 million householders around the world (IRRI, 2002). It is one of the crops responsible for the so-called green revolution that happened in the 1960s and 1970s. In addition of having strong breeding programs in all different regions around the world, this crop has three Consultative Groups on International Agricultural Research (CGIAR) centers with the mandate to work with rice: the International Rice Research Institute (IRRI), with global mandate; the West Africa Rice Development Association (WARDA), with mandate to work in West Africa; and the International Centre for Tropical Agriculture (CIAT), with the regional mandate for Latin America.
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Wheat (various species of the genus Triticum) is a grass originating from the Levant area of the Middle East. However, only hexaploid common wheat (Triticum eastivum), and tetraploid durum wheat (Triticum turgidum ssp. durum) are presently cultivated worldwide. Not only is wheat an important crop today, it may well have influenced human history. Wheat was a key factor enabling the emergence of civilization because it was one of the first crops that could be easily cultivated on a large scale, and had the additional advantage of yielding a harvest that provides long-term storage of food. Today, there are different classes and uses of wheat. Although, it is mainly used as a staple food to make flour for leavened, flat and steamed breads, wheat can also be used as livestock feed, for fermentation to make beer and other alcoholic liquids, and recently, as a source of bio-energy. Global wheat production must increase at about 2% annually to meet future demands. The potential of increasing the global arable land is limited; hence, future increases in wheat production must be achieved by enhancing the wheat productivity to the land already in use. The objectives of most breeding programs include: high and stable yields, superior end-use quality, desirable agronomic characteristics, biotic (mainly, pests) resistance, and abiotic (environmental stresses) tolerance. While it is virtually impossible to combine all these characteristics into a single ‘perfect’ variety, continuous breeding efforts toward achieving these objectives will ensure that new varieties possess as many desirable and economic traits as possible. Details of the different breeding approaches to enhance modern wheat breeding are discussed in this chapter.
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Breeding for complex multigenic phenotypic quality characters in cereals by chemical analyses and functional pilot tests is traditionally a slow and expensive process. The development of new instrumental screening methods for complex quality traits evaluated by multivariate data analysis has during the last decades revolutionised the economy and scale in breeding for quality. The traditional explorative plant breeding view is pragmatically oriented to manipulate the whole plant and its environment by “top down” observation and selection to improve complex traits, such as yield and baking quality. The new molecular and biochemical techniques are promising in increasing the genetic variation by breaking the barriers of species and in explaining the chemical and genetic basis of quality. In molecular biology traits are seen “bottom up” from the genome perspective, for example, to find genetic markers by quantitative trait loci (QTL). To improve efficiency the plant breeder can now complement his classical tools of observation by overviewing the whole physical–chemical composition of the seed by near infrared spectroscopy (NIRS) from a Principal Component Analysis (PCA) score plot to connect to genetic, (bio)chemical, and technological data through pattern recognition data analysis (chemometrics). Genes and genotypes can also be directly evaluated as imprints in NIR spectra. Recent applications in NIR technology by ”data breeding” demonstrate manual selection for complex high-quality traits and seed genotypes directly from a PCA score plot. New equipment makes automatic analysis and sorting for complex quality traits possible both in bulk and on single seed basis. Seed sorting can be used directly in seed production and to speed up selection for quality traits in early generations of plant breeding and to document genetic diversity in gene banks.
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We introduce in this chapter a series of linear and bilinear models for the study of genotype by environment interaction (GE) and adaptation. These models increasingly incorporate available genetic, physiological, and environmental information for modelling genotype by environment interaction (GE). They are based on analyses of variance and regression and can be formulated in most standard statistical packages. We use the data of a series of trials for 65 barley genotypes (G) grown in 12 environments (E) for illustration and interpretation of the output of such analyses. We aim at identifying key environmental covariables to explain differential phenotypic responses as well as to estimate genotypic sensitivities to these covariables. Using genetic covariables in the form of molecular markers, we partition genotypic main effect terms and GE terms into main effects for quantitative trait loci (QTL) and QTL by environment interaction (QTL.E). The QTL.E estimates can be further regressed on environmental covariables to target differential QTL expression potentially related to environmental factors. We believe that the statistical models that describe GE in direct association to genetic, physiological, and environmental information provide insight in GE and facilitate the development and deployment of new breeding strategies
Article
Langdon durum D-genome disomic substitution lines were used to study the chromosome locations of adult-plant leaf rust resistance genes identified from tetraploid wheat accessions. The accessions are 104 (Triticum turgidum subsp. dicoccum var. arras) and 127 (T. turgidum subsp. durum var. aestivum). The complete sets of the substitution lines were crossed as female parents with the accessions and F1 double monosomic individuals selected at metaphase I. Segregating F2 individuals were inoculated during the flag leaf stage with pathotype UVPrt2 of Puccinia triticina. The substitution analysis involving accession 104 showed that the gene for leaf rust resistance is located on chromosome 6B. The analysis with accession 127 indicated that chromosome 4A carries a gene for leaf rust resistance. The two novel genes are temporarily designated as Lrac104 and Lrac127, respectively from accessions 104 and 127.
Article
Wild relatives of common wheat, Triticum aestivum, and related species are an important source of disease and pest resistance and several useful traits have been transferred from these species to wheat. C-banding and in situ hybridization analyses are powerful cytological techniques allowing the detection of alien chromatin in wheat. C-banding permits identification of the wheat and alien chromosomes involved in wheat-alien translocations, whereas genomic in situ hybridization analysis allows determination of their size and breakpoint positions. The present review summarizes the available data on wheat-alien transfers conferring resistance to diseases and pests. Ten of the 57 spontaneous and induced wheat-alien translocations were identified as whole arm translocations with the breakpoints within the centromeric regions. The majority of transfers (45) were identified as terminal translocations with distal alien segments translocated to wheat chromosome arms. Only two intercalary wheat-alien transloctions were identified, one induced by radiation treatment with a small segment of rye chromosome 6RL (H25) inserted into the long arm of wheat chromosome 4A, and the other probably induced by homoeologous recombination with a segment derived from the long arm of a group 7 Agropyron elongatum chromosome with Lr19 inserted into the long arm of 7D. The presented information should be useful for further directed chromosome engineering aimed at producing superior germplasm.
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Wheat streak mosaic virus (WSMV; Family: potyviridae; Genus: Tritimovirus) is a major threat to winter wheat (Triticum aestivum L. em. Thell) production worldwide, yet little is known about the genetic control of resistance. Our objective was to determine the mode of inheritance and type of gene action of WSMV resistance in two winter wheat crosses involving a resistant line, OK65C93-8, and two susceptible cultivars, Tandem and Vista. For each cross, parents, F1, F2, and backcross plants were inoculated and evaluated for WSMV resistance in two replicated greenhouse experiments. Generation means analysis indicated that additive, dominance, and epistatic effects were all involved in the inheritance of WSMV resistance. Broad-sense heritability estimates for visual symptom rating and ELISA values were high for both crosses (0.84–0.91). Narrow-sense heritability estimates were low in the Tandem/OK65C93-8 cross (0.43–0.45) and moderate in the Vista/OK65C93-8 cross (0.71–0.74). Due to the presence of greater non-additive gene effects combined with low narrow-sense heritability in the Tandem/OK65C93-8 cross, selecting for WSMV resistance in this cross would be complex if using conventional methods. On the other hand, the significant contribution of additive gene effects combined with moderate narrow-sense heritability in the Vista/OK65C93-8 cross suggested that it could be exploited to select for WSMV resistance. Progress from selection for WSMV resistance in early generations of winter wheat may vary among populations as indicated in this study. Therefore, evaluating genetic control of parental combinations may be warranted prior to selecting for WSMV resistance from this source.
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Wheat streak mosaic virus (WSMV) has been newly documented in Australia. The vulnerability of contemporary Australian elite wheat germplasm prompted a survey for effective resistance against an Australian isolate,WSMV-ACT. This study confirms the effectiveness of previously reported sources of resistance and shows that new sources of resistance also confer protection. The resistance derived from Thinopyrum intermedium (Wsm1) as a 4D translocation and a new 4A translocation, and two bread wheat resistances, Wsm2 and the new source c2652, were effective againstWSMV-ACT in glasshouse experiments. Wsm1 was effective at lower temperatures but ineffective above 20_C, a temperature sensitivity shared with many of the derivatives of Wsm2 except for one new selection which was effective at 26_C. True wheats c2652 and Wsm2 selection CA745, and amphiploids Zhong1, Zhong2, Zhong4, Zhong5, TAF46, Summer1, Ot38 and OK7211542 were uniformly resistant at 20, 25 and 28_C. New sources of resistance were identified in a Th. scirpeum-wheat amphiploid, B84-994, and in chromosome addition lines Z2, Z6 and TAi27, derived from wheat-Th. intermedium partial amphiploids. Several new, tightly linked SSR, RAPD and EST-ILP PCR markers were developed for tracking the various Th. intermedium translocations associated with Wsm1, including the smaller translocations on wheat chromosome 4AS and 4DS. Three markers for the 4A-Wsm1 translocation were validated on a segregating breeding population.
Article
The Wheat Genetics Resource Center, a pioneering center without walls, has served the wheat genetics community for 25 years. The Wheat Genetics Resource Center (WGRC) assembled a working collection of over 11,000 wild wheat relatives and cytogenetic stocks for conservation and use in wheat genome analysis and crop improvement. Over 30,000 samples from the WGRC collection of wheat wild relatives, cytogenetic stocks, and improved germplasm have been distributed to scientists in 45 countries and 39 states in the United States. The WGRC and collaborators have developed standard karyotypes of 26 species of the Triticum/Aegilops complex, rye, and some perennial genera of the Triticeae. They have developed over 800 cytogenetic stocks including addition, substitution, and deletion lines. The anchor karyotypes, technical innovations, and associated cytogenetic stocks are a part of the basic tool kit of every wheat geneticist. They have cytogenetically characterized over six‐dozen wheat–alien introgression lines. The WGRC has released 47 improved germplasm lines incorporating over 50 novel genes against pathogens and pests; some genes have been deployed in agriculture. The WGRC hosted over three‐dozen scientists especially from developing countries for advanced training. The WGRC was engaged in international agriculture through several collaborating projects. Particularly noteworthy was the collaborative project with Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) on the production of synthetic wheats. It is estimated that “by the year 2003–2004, 26% of all new advanced lines made available through CIMMYT screening nurseries to cooperators for either irrigated or semi‐arid conditions were synthetic derivatives.” The WGRC is applying genomics tools to further expedite the use of exotic germplasm in wheat crop improvement.
Thesis
Wheat streak mosaic virus (WSMV) is a new virus of wheat crop in Australia. Discovered in the Australian Capital Territory (ACT) in 2003, the virus has put Australian commercial bread wheat at a risk of major losses. Although, the virus is naturally transmitted by Wheat curl mites (WCM), some of the Australian farming community expressed concerns that grazing of early sown, dual-purpose wheat for winter forage may have a role in the spread of WSMV. We probed this issue in a series of experiments with housed sheep grazing on WSMV infected wheat plants. However, we find no evidence for the suggestion that grazing sheep spread the WSMV between plants in a grazed wheat crop as a consequence of the grazing process itself. We tested for natural resistance against WSMV in diverse germplasm including three different known resistance sources in cultivated wheat. Previously reported resistances were effective against the Australian isolate of WSMV. Some accessions of these resistances were ineffective at higher temperatures (all Wsm1 and most Wsm2 accessions); some were reported to have linked negative agronomic traits (most accessions of Wsm1). Two exceptions were c2652 and Wsm2 accession CA745 which were very effective at controlled higher temperatures (28{u00B0}C), in the glasshouse, and also protected plants from symptoms and yield loss following WSMV mechanical inoculation in the field, making these two sources particularly useful in the relatively warm Australian agro-climate. New molecular markers were developed for the various derivatives of Wsm1 resistance that should help speed up the breeding of resistance into wheat cultivars. These Wsm1 markers are now being used by CSIRO for breeding Wsm1-resistance into elite wheat cultivars. Furthermore, we developed and tested two independent transgenic strategies based on intron-hairpin RNA (ihpRNAi) and artificial microRNAs (amiRNA). Both strategies were effective in conferring immunity in transgenic wheat to mechanically inoculated WSMV. We classified this resistance as immunity by four criteria: no disease symptoms were produced; Enzyme linked immunosorbent assay (ELISA) readings were as in un-inoculated plants; viral sequences could not be detected by RT-PCR from leaf extracts; and leaf extracts failed to give infections in susceptible plants when used in test-inoculation experiments. We developed ihpRNA or RNAi based immune transgenic wheat by designing an RNAi construct to target the Nuclear inclusion protein 'a' (NIa) gene of WSMV. The Northern and Southern blot hybridization analysis indicated the ihpRNA transgene integrated into the wheat genome and was processed into typical 21-24 nucleotide long siRNAs and correlated with immunity in transgenic plants. In order to achieve amiRNA immunity, we designed five artificial microRNAs (amiRNA) against different portions of the WSMV genome, utilising published miRNA sequence and folding rules; these amiRNAs were incorporated into five duplex arms of the polycistronic rice primary microRNA (pri-miR395) and transformed into wheat. Southern blot hybridisation showed that the transgene was stably integrated into the wheat genome and processed into small RNAs, both correlating with transgenic resistance against WSMV. As a consequence of the work described in this thesis, the wheat industry in Australia and abroad has both conventional and transgenic options for the control of this serious viral pathogen.
Article
The development of wheat (Triticum aestivum L.) cultivars that are resistant to Wheat streak mosaic virus (WSMV), yet competitive in yield under nondiseased conditions, is an objective for breeding programs in the Great Plains. This field study was conducted to compare classical and transgenic sources of resistance to WSMV. Three sets of germplasm were evaluated. These included adapted cultivars with various levels of tolerance, transgenic wheat lines containing viral coat protein or replicase sequences from WSMV that showed resistance in greenhouse trials, and germplasm with resistance to WSMV due to a translocated segment of chromosome 4Ai-2 from Thinopyrum intermedium (Host) Barkworth and Dewey containing Wsm1. A replicated field trial was conducted at Bozeman, MT, over a two-year period to evaluate the effectiveness of these different sources of resistance to mechanical inoculation of WSMV. Adapted cultivars differed in their ability to tolerate WSMV with mean reductions in yield over the two years ranging from 41 to 74%. Incorporation of the replicase or coat protein gene from WSMV did not provide field resistance to viral infection and in general, transgenic lines yielded less than their parent cultivar, 'Hi-Line'. Wheat-Thinopyrum lines positive for a DNA marker linked to the Wsm1 gene had significantly reduced yield losses ranging from 5 to 39% compared with yield losses of 57 to 88% in near isogenic lines not having the Wsm1 gene. Yield of lines with Wsm1 in the absence of disease ranged from 11 to 28% less than yield of lines without Wsm1. Our results suggest Wsm1 provides the best source of WSMV resistance but a yield penalty may exist because of the presence of the translocation.
Article
The introduction of alien genetic variation from the genus Thinopyrum through chromosome engineering into wheat is a valuable and proven technique for wheat improvement. A number of economically important traits have been transferred into wheat as single genes, chromosome arms or entire chromosomes. Successful transfers can be greatly assisted by the precise identification of alien chromatin in the recipient progenies. Chromosome identification and characterization are useful for genetic manipulation and transfer in wheat breeding following chromosome engineering. Genomic in situ hybridization (GISH) using an S genomic DNA probe from the diploid species Pseudoroegneria has proven to be a powerful diagnostic cytogenetic tool for monitoring the transfer of many promising agronomic traits from Thinopyrum. This specific S genomic probe not only allows the direct determination of the chromosome composition in wheat-Thinopyrum hybrids, but also can separate the Th. intermedium chromosomes into the J, J(S) and S genomes. The J(S) genome, which consists of a modified J genome chromosome distinguished by S genomic sequences of Pseudoroegneria near the centromere and telomere, carries many disease and mite resistance genes. Utilization of this S genomic probe leads to a better understanding of genomic affinities between Thinopyrum and wheat, and provides a molecular cytogenetic marker for monitoring the transfer of alien Thinopyrum agronomic traits into wheat recipient lines.
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Wheat streak mosaic virus (WSMV) causes streak mosaic disease in wheat ( Triticum aestivum L.) and has been an important constraint limiting wheat production in many regions around the world. Wsm2 is the only resistance gene discovered in wheat genome and has been located in a short genomic region of its chromosome 3B. However, the sequence nature and the biological function of Wsm2 remain unknown due to the difficulty of genetic manipulation in wheat. In this study, we tested WSMV infectivity among wheat and its two closely related grass species, rice ( Oryza sativa ) and Brachypodium distachyon . Based on the phenotypic result and previous genomic studies, we developed a novel bioinformatics pipeline for interpreting a potential biological function of Wsm2 and its ancestor locus in wheat. In the WSMV resistance tests, we found that rice has a WMSV resistance gene while Brachypodium does not, which allowed us to hypothesize the presence of a Wsm2 ortholog in rice. Our OrthoMCL analysis of protein coding genes on wheat chromosome 3B and its syntenic chromosomes in rice and Brachypodium discovered 4,035 OrthoMCL groups as preliminary candidates of Wsm2 orthologs. Given that Wsm2 is likely duplicated through an intrachromosomal illegitimate recombination and that Wsm2 is dominant, we inferred that this new WSMV-resistance gene acquired an activation domain, lost an inhibition domain, or gained high expression compared to its ancestor locus. Through comparison, we identified that 67, 16, and 10 out of 4,035 OrthoMCL orthologous groups contain a rice member with 25% shorter or longer in length, or 10 fold more expression, respectively, than those from wheat and Brachypodium. Taken together, we predicted a total of 93 good candidates for a Wsm2 ancestor locus. All of these 93 candidates are not tightly linked with Wsm2 , indicative of the role of illegitimate recombination in the birth of Wsm2 . Further sequence analysis suggests that the protein products of Wsm2 may combat WSMV disease through a molecular mechanism involving protein degradation and/or membrane trafficking. The 93 putative Wsm2 ancestor loci discovered in this study could serve as good candidates for future genetic isolation of the true Wsm2 locus.
Chapter
This chapter summarizes the scientific and technical knowledge for durum wheat breeding, giving some examples of the methods applied in national programs. Section 1 refers to the importance of durum wheat in the world. Sections 2 and 3 give technical details on genetic diversity and the choice of germplasm, while the main varietal groups are explained in Section 4. Information about the major breeding achievements, current goals of breeding and breeding methods and techniques are covered by Sections 5, 6 and 7 respectively. The integration of new biotechnologies, particularly marker assisted selection, into breeding programs is described on Section 8, while information about foundation seed production and intellectual property rights are given on Section 9.
Chapter
Rye (Secale cereale L.) is mainly a European cereal with about 75% of the global production growing in Russia, Belarus, Poland, Germany, and Ukraine. It has the best overwintering ability, and the highest tolerance to drought, salt, or aluminium stress from all small-grain cereals. Harvest is used for bread making, feed, and in growing demands for ethanol and biomethane production as a renewable energy source. Hybrid rye is competitive to triticale and wheat also on better soils and grown in Germany on about 70% of the total rye acreage. Rye developed in the Middle East as a secondary crop, cultivated rye has its greatest diversity in landraces and populations from Central and East Europe. Their utility for breeding has considerably increased by progress in marker-based introgression of donor chromosome segments. Resistance breeding is presently focused on leaf and stem rust (Puccinia recondita, P. graminis f.sp. secalis), ergot (Claviceps purpurea), and Fusarium diseases. Leaf blotch (Rhynchosporium secalis) and soilborne viruses might gain more attention in the future. Main breeding goals are grain yield, straw shortness, lodging resistance, high kernel weight, tolerances to pre-harvest sprouting and abiotic stresses. Population varieties comprise open-pollinated and synthetic varieties. Both are derived from self-incompatible breeding populations which are steadily improved by recurrent half- or full-sib selection. Open pollinated varieties (OPVs) constitute selected fractions of those populations whereas synthetic varieties are composed of specifically selected parents from which they can identically be reconstituted. Most modern population varieties contain germplasm from two or more genetically distant gene pools. Hybrid breeding is based on self-fertile gene pools and cytoplasmic genic male sterility (CMS) is used as hybridizing mechanism. Long-lasting breeding cycles are needed for the development of seed parent lines since testcrossing is only possible after the inbred lines have been converted to CMS analogues by repeated backcrossing. Options to speed up this process are discussed. Development of restorer lines is straightforward once effective restorer genes have been introduced to the respective breeding populations. Recurrent improvement of fertility restoration is most efficiently accomplished by recombining selected inbred lines after the first or second testcrossing stage. Commercial hybrid seed production requires well-skilled farmers, careful seed processing, and deliberate logistics since rye produces huge amounts of pollen which may be transported over long distances. Even the slightest genetic contamination of the CMS pre-basis and basis seed production may render the respective seed lots worthless for subsequent multiplication. To reduce the cost of the final step of seed production, the CMS seed parent and the pollinator parent are grown as a mixture in a 95:5 ratio. Thus, only about 95% of the certified seed consists of true hybrid seed. Whereas the remainder 5% are randomly intermated plants of the pollinator. However, the latter generally are poor competitors and therefore do not impair the yielding performance of the ‘hybrid’ stand. In the last decades, population and hybrid breeding led to substantial progress in grain yield and other traits.
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Wheat is the most widely grown crop in the world. Winter wheat is primarily common wheat (2n = 6x = 42) which has extensive germplasm resources that are used in breeding, often for disease and insect resistance. Though wheat can be used as a forage crop and its grain for animal feed, the primary uses of common wheat are to make products used for human consumption; hence end-use quality is also a major breeding objective. The quality characteristics of these products are often associated with kernel hardness which affects milling, kernel color, and specific climatic zones or regions. The soft red and white wheat cultivars of the Eastern and Southeastern U.S. are generally used to make breakfast cereals, cookies, cakes, and crackers. The hard red and white wheat cultivars of the Great Plains are used predominantly for leavened products such as bread. The soft white wheat cultivars of the Pacific Northwest are often exported and used to make noodles or steam breads. These end-uses and production (adaptation) regions determine the germplasm pools used by wheat breeders. All of the common self pollinated breeding methods are used to breed new wheat cultivars. The choice of breeding method is usually based upon breeding objective and program resources. Breeding methods and objectives are evolving with new technology and market changes.
Article
Wheat streak mosaic virus (WSMV) and Triticum mosaic virus (TriMV) are important viruses of wheat (Triticum aestivum L.) in the Great Plains of United States. In addition to agronomic practices to prevent damage from these viruses, temperature sensitive resistance genes Wsm1, Wsm2 and Wsm3, have been identified. However, threshold temperatures for Wsm1 and Wsm3 have not been clearly defined. To better understand these two resistance genes, wheat lines C.I.15092 (Wsm1), KS96HW10–3 (Wsm1), and KS12WGGRC59 (Wsm3) were evaluated for WSMV resistance at 27, 30, 33 and 35 °C and for TriMV resistance at 18, 21, 24, 27, 30, 33 and 35 °C. The results showed that only C.I.15092 remained resistant at 30 °C for both viruses. This line also tolerated TriMV at 33 and 35 °C with less sever symptom and lower infection rates. Wheat lines KS96HW10–3 and KS12WGGRC59 hold resistance to TriMV up to 21 °C. Molecular marker results suggested that the resistance in C.I.15092 is most probably conditioned by the resistance gene Wsm1 and additional gene(s) other than Wsm2 and Wsm3.
Article
Wheat streak mosaic (WSM), caused by Wheat streak mosaic virus (WSMV), is a devastating disease in wheat (Triticum aestivum L.) in the Great Plains of North America. Use of resistance is an effective and environmentally sound method to control the disease. In this study, six wheat genotypes were compared for their responses to WSMV infection under growth chamber conditions. The three resistant genotypes, KS96HW10-3 (Wsm1), Mace (Wsm1), and CO960293-2, had disease scores significantly lower than the remaining three genotypes without major resistance. Disease in TAM 111 and TAM 112 was consistently less severe than Karl 92. A population consisting of 188 F(2:3) families derived from the cross CO960293-2 x TAM 111 was used for determining inheritance of the WSMV resistance and for molecular mapping of the resistance in CO960293-2. Data on segregation of resistance indicated that the resistance in CO960293-2 is conditioned by a single dominant gene, which was named Wsm2. Transgressive segregation toward susceptibility occurred in the population suggesting a minor gene in the moderately susceptible parent TAM 111, which was not allelic to Wsm2. Wsm2 was mapped to the short arm of chromosome 3B with two flanking simple sequence repeat markers. The single dominant gene inheritance for WSMV resistance in CO960293-2 has been consistent with the observations that the resistance can be readily transferred to adapted cultivars.
Article
Wheat streak mosaic virus (WSMV), is a potentially devastating disease of common wheat (Triticum aestivum L.) in the Great Plains of North America. So far, two genes conferring resistance to WSMV have been named and used in cultivar improvement. Here we report a new source of resistance that was derived from a wheat-Thinopyrum intermedium (Host) Barkworth & D.R. Dewey ditelosomic addition line containing, in addition to the wheat chromosome complement, a pair of long arm telochromosomes from Th. intermedium previously believed to be of group-4 origin. New molecular marker and genomic in situ hybridization analysis revealed that this telochromosome is homeologous to the group-7 long arms and belongs to the S genome of Th. intermedium. Accordingly, this chromosome was designated as 7S#3L. One compensating Robertsonian translocation was obtained where the 7S#3L arm was translocated to the short arm of wheat chromosome 7B, resulting in the T7BS.7S#3L translocation chromosome. Homozygous T7BS.7S#3L lines were evaluated for their resistance to WSMV and Triticum mosaic virus (TriMV). The T7BS.7S#3L stock confers resistance to WSMV at 18 and 24 degrees C. The T7BS.7S#3L stock also confers resistance to TriMV at 18 C but is not effective above 24 degrees C. Based on chromosome position and effective resistance to WSMV at 24 degrees C where both Wsm1 and Wsm2 are ineffective, the new gene in T7BS.7S#3L is designated as Wsm3.
Article
As the result of several decades of traditional breeding on the resistance of wheat to viruses, foreign scientists have succeeded in identifying resistance sources (cultivar Geneva, Thinopyrum species) and resistance genes (Bdv1, Bdv2, Bdv3, Wsm1) that can be efficiently used against the cereal viruses attacking wheat, including Barley yellow dwarf viruses (BYDV), Cereal yellow dwarf viruses (CYDV), Wheat streak mosaic virus (WSMV) and Wheat spindle streak mosaic virus (WSSMV). Some of the lines carrying the translocation do not yet have a yield average as high as that of cultivated varieties, though the use of varieties and breeding lines carrying resistance genes is the most effective way of maintaining yield averages in the case of infection. Some lines contain a combination of several resistance genes, and these gene pyramids afford protection against a number of viruses. The mechanism of resistance is partly known (Bdv2), but in some cases further research will be required (cultivar Geneva). The advantage of using resistance sources in wheat has been recognised in Hungary, as elsewheres and it is hoped that they will soon spread on an increasingly wide scale.
Article
Wheat streak mosaic virus (WSMV) is a destructive pathogen in wheat (Triticum aestivum L.). Host resistance is the most effective way to control this virus. To date, Wsm2 is the only wheat resistance gene that is genetically mapped. The objective of this study was to identify germplasm lines that might carry resistance genes different from Wsm2. Eight newly reported resistant germplasm lines were examined by allelic tests. To validate the allelic test results, five of them were further analysed for the inheritance of WSMV resistance. A Wsm2-linked marker was also genotyped on populations developed for the inheritance study. Our results suggested that the WSMV resistance in lines CItr9358, PI225288, PI243652, PI245439, PI245526 and PI478095 was controlled by either Wsm2 or a gene very closely linked to Wsm2. The resistance in PI243753 and PI321730, however, is likely controlled by a gene different from, but linked to Wsm2. The resistance in PI321730 might also involve some minor genes. This study provided useful information for breeders to select appropriate resistant lines to improve WSMV resistance in wheat.
Article
Thinopyrum species are promising sources of resistance to wheat streak mosaic virus (WSMV), a devastating disease of wheat, and its vector, the wheat curl mite (WCM). Different partial amphiploid lines possessing resistance to WSMV and WCM derived from Triticum aestivum x Thinopyrum crosses were characterised using in situ hybridization (GISH) to determine the relationship between the genomic and the chromosomal composition of the alien wheat-Thinopyrum hybrid lines and resistance to WSMV and the WCM. Most partial amphiploids were resistant to WSMV. However, only a few of them were resistant to the WCM. Among wheat-Th. intermedium derivatives, the partial amphiploids Montana-2 (MT-2) and Zhong 1-grey were identified as the new sources of resistance against both WSMV and WCM. The genomic composition of the alien chromosomes present in these WSMV- and WCM-resistant lines was analyzed by GISH using S genomic DNA from Pseudoroegneria strigosa (2n=2x=14, SS) as a probe. The results showed that the alien genomes of the resistant partial amphiploids MT-2 and Zhong 1-grey were synthetic, consisting of different chromosomes from the S, JS and J genomes derived from their Thinopyrum parents. MT-2 had variable chromosome numbers consisting of 8-10S, 8JS, 13J genome chromosomes, and 2S-JS translocations in addition to 23-24 wheat chromosomes. Zhong 1-grey had 42 wheat, 2S, 4JS and 4J chromosomes. The JS genome chromosomes were also present in another WSMV- and WCM- resistant partial amphiploid wheat-Th. ponticum line (Agrotana). There were no JS genome chromosomes present in WCM-susceptible lines TAF46 and Otrastayashchaya 38 (OT), indicating that the chromosome carrying the genes for resistance to the WCM might belong to the JS genome. Translocated chromosomes involving the S and JS genomes were also observed in the resistant, partial amphiploid MT-2, indicating exchange of genetic information among these genomes. The identification of the new sources of resistance to WSMV and WCM has the potential to broaden the genetic basis of wheat breeding programs for this important disease and its vector.
Article
Wheat streak mosaic virus (WSMV) is an important pathogen in wheat that causes significant yield losses each year. WSMV is typically controlled using cultural practices such as the removal of volunteer wheat. Genetic resistance is limited. Until recently, no varieties have been available with major resistance genes to WSMV. Two resistance genes have been derived from Thinopyrum intermedium through chromosome engineering, while a third gene was transferred from bread wheat through classical breeding. New sources of resistance are needed and synthetic wheat lines provide a means of accessing genetic variability in wheat progenitors. A collection of wheat synthetic lines was screened for WSMV resistance. Four lines, 07-SYN-27, -106, -164, and -383 had significant levels of resistance. Resistance was effective at 18 °C and virus accumulation was similar to the resistant control, WGGRC50 containing Wsm1. At 25 °C, resistance was no longer effective and virus accumulation was similar to the susceptible control, Tomahawk.
Chapter
Wild relatives of common wheat, Triticum aestivum, are an important source for disease and pest resistance. Recently we reviewed the status of wheat-alien translocations conferring resistance to diseases and pests (45). Since then, several new transfers were reported and markers linked to resistance genes identified. Here we present an update of the available information on wheat-alien translocations.
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Wheat streak mosaic virus (WSMV) causes streak mosaic disease in wheat ( Triticum aestivum L.) and has been an important constraint limiting wheat production in many regions around the world. Wsm2 is the only resistance gene discovered in wheat genome and has been located in a short genomic region of its chromosome 3B. However, the sequence nature and the biological function of Wsm2 remain unknown due to the difficulty of genetic manipulation in wheat. In this study, we tested WSMV infectivity among wheat and its two closely related grass species, rice ( Oryza sativa ) and Brachypodium distachyon . Based on the phenotypic result and previous genomic studies, we developed a novel bioinformatics pipeline for interpreting a potential biological function of Wsm2 and its ancestor locus in wheat. In the WSMV resistance tests, we found that rice has a WMSV resistance gene while Brachypodium does not, which allowed us to hypothesize the presence of a Wsm2 ortholog in rice. Our OrthoMCL analysis of protein coding genes on wheat chromosome 3B and its syntenic chromosomes in rice and Brachypodium discovered 4,035 OrthoMCL groups as preliminary candidates of Wsm2 orthologs. Given that Wsm2 is likely duplicated through an intrachromosomal illegitimate recombination and that Wsm2 is dominant, we inferred that this new WSMV-resistance gene acquired an activation domain, lost an inhibition domain, or gained high expression compared to its ancestor locus. Through comparison, we identified that 67, 16, and 10 out of 4,035 OrthoMCL orthologous groups contain a rice member with 25% shorter or longer in length, or 10 fold more expression, respectively, than those from wheat and Brachypodium. Taken together, we predicted a total of 93 good candidates for a Wsm2 ancestor locus. All of these 93 candidates are not tightly linked with Wsm2 , indicative of the role of illegitimate recombination in the birth of Wsm2 . Further sequence analysis suggests that the protein products of Wsm2 may combat WSMV disease through a molecular mechanism involving protein degradation and/or membrane trafficking. The 93 putative Wsm2 ancestor loci discovered in this study could serve as good candidates for future genetic isolation of the true Wsm2 locus.
Article
Wheat streak mosaic virus (WSMV), vectored by the wheat curl mite (Acer tulipae), is an important disease of wheat (Triticum aestivum L.) in the North American Great Plains. Resistant varieties have not been developed for two primary reasons. First, useful sources of resistance have not been available, and second, field screening for virus resistance is laborious and beyond the scope of most breeding programs. The first problem may have been overcome by the development of resistance to both the mite and the virus by the introgression of resistance genes from wild relatives of wheat. To help address the second problem, we have developed polymerase chain reaction (PCR) markers linked to the WSMV resistance gene Wsm1. Wsm1 is contained on a translocated segment from Agropyron intermedium. One sequence-tagged-site (STS) primer set (WG232) and one RAPD marker were found to be linked to the translocation containing Wsm1. The diagnostic RAPD band was cloned and sequenced to allow the design of specific PCR primers. The PCR primers should be useful for transferring Wsm1 into locally adapted cultivars.
Article
Development of wheat (Triticum aestivum L.) cultivars resistant to Wheat streak mosaic virus (WSMV) that remain productive in the absence of the disease would benefit wheat growers. A wheat germplasm (KS93WGRC27) carrying a Thinopyrum intermedium (Host) Barkworth and Dewey chromosome 4Js translocation conferring WSMV resistance was used to develop spring wheat populations segregating for WSMV resistance. Four populations, consisting of a total of 22 translocation-positive (WSMV-resistant), 36 translocationnegative (WSMV-susceptible), and eight parental lines, were grown as a randomized complete block with three replications at Bozeman and Conrad, MT, in 1998 and 1999. Treatments were arranged as a split plot with populations as main plots and progeny and parents as subplots. The agronomic performance of resistant and susceptible lines was compared under inoculated and noninoculated conditions to assess the effectiveness of the WSMV resistance gene and to determine the effects of the Thinopyrum translocation in the absence of disease. A small but significant decrease in yield was observed for noninoculated resistant lines in contrast to susceptible lines. However, the yield range of resistant entries suggests that the recovery of parental yield was possible. The resistance source was highly effective in limiting virus accumulation and yield losses to WSMV, resulting in only a 5% yield reduction in resistant lines under inoculated conditions compared with 32% for susceptible lines. In all instances where WSMV was introduced to field trials, the Thinopyrum translocation provided a significant benefit for resistant lines when compared with susceptible lines. The T. intermedium translocation present in resistant lines had no detrimental effects on end-use quality or other agronomic traits.
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Grain sorghum [Sorghum bicolor (L.) Moench] is a relatively drought- and heat-resistant crop. World wide it is used as feed and food grain. In Australia, it is used as a feed grain and is grown under rain-fed conditions. Water availability to the plant is the major constraint to production. This chapter describes aspects of the Department of Primary Industries and Fisheries sorghum breeding program. The overall aim of this program is the development of germplasm which is licensed to the private sector for the development of hybrid cultivars and use in their breeding programs. This latter aspect has ensured program focus and the ready adoption by industry of program products. The specific objectives of the program are the development of germplasm with resistance to the sorghum midge, drought resistance (stay-green) and yield. High levels of midge resistance have been developed and combined with significant levels of stay-green and improved yield under Australian conditions.
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