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Stem rust seedling resistance genes in Ethiopian wheat cultivars and breeding lines.
B Admassu, W Friedt, F Ordon
African Crop Science Journal , 2012,
Abstract: Stem rust caused by Puccinia graminis f. sp. tritici is one of the major biotic limiting factors for wheat production in Ethiopia. Host plant resistance is the best option to manage stem rust from its economic and environmental points of view. Wheat cultivars are released for production without carrying race specific tests against stem rust. Hence, genes responsible for resistance in commercial wheat cultivars are not known. The objective of this study was to postulate stem rust resistance genes present in Ethiopian commercial wheat cultivars and advanced breeding lines. Thirty durum wheat (19 commercial cultivars and 11 breeding lines) and 30 bread wheat (20 commercial cultivars and 10 breeding lines) were tested for gene postulation. Stem rust infection types produced on wheat cultivars and breeding lines by ten Pgt races was compared with infection types produced on 40 near isogenic lines carrying single stem rust resistance genes. A total of 11 stem rust resistance genes (Sr5, Sr7a, Sr7b, Sr8a, Sr9e, Sr11, Sr21, Sr27, Sr29, Sr30 and Sr37) were postulated to be present either singly or in combination in the durum and wheat cultivars and breeding lines. Except Sr30, the other postulated genes were susceptible to most of the prevalent Puccinia graminis f. sp. tritici races in Ethiopia. Since Sr30 is also ineffective against Ug99, a gene management strategy that incorporates a combination of genes (gene pyramiding) that provide sufficient protection should be devised to achieve a durable control of stem rust. In addition, the significance of Sr27, Sr29 and Sr37 has to be investigated for Ethiopian agriculture. Key Words: Durum wheat, isogenic lines, Puccinia graminis
Occurrence of the rust resistance gene Lr37 from Aegilops ventricosa in Argentine cultivars of wheat
Bulos,Mariano; Echarte,Mariel; Sala,Carlos;
Electronic Journal of Biotechnology , 2006,
Abstract: leaf rust of wheat (triticum aestivum l.) caused by the fungus puccinia triticina (formerly p. recondita f. sp. tritici), is one of the most important foliar diseases of this crop. lr37 rust resistance gene, which confers resistance in wheat against leaf rust, was introgressed into cultivated wheat from aegilops ventricosa tausch. rust races with virulence to lr37 have been identified in different countries, but it still provides resistance to a wide range of races and is useful in combination with other resistance genes. there are no reports about the presence, frequency and origin of lr37 in argentinean wheat cultivars. in this work, we analyzed 88 registered argentinean wheat cultivars developed by different breeding companies and institutions during the last 15 years by means of a molecular marker which is diagnostic of the 2ns-2as translocation which carries lr37. only 4 cultivars showed the amplification product associated with this chromosome fragment. these four cultivars which carry the translocated 2ns-2as chromosome were registered by the same breeding company during the last seven years and all of them have european germplasm in their genealogy. to the best of our knowledge this is the first report of the presence of lr37 in registered south american cultivars.
Biotic Stress Resistance in Wheat - Breeding and Genomic Selection Implications
E. Todorovska , N. Christov , S. Slavov , P. Christova , D. Vassilev
Biotechnology & Biotechnological Equipment , 2009, DOI: 10.2478/V10133-009-0006-6
Abstract: Leaf and stem rust are among the most important diseases in wheat. The selection of wheat genotypes with combination of non-race-specific genes defining durable resistance over years as well as race specific genes at seedling stage is a task of high importance for breeding programs. Gene pyramiding using conventional method is difficult and time-consuming because it requires simultaneous tests of the same wheat breeding materials with several different rust races before making selection. DNA-based molecular markers have several advantages over the traditional phenotype trait selection. Molecular markers can be used to tag rust resistance genes and further to be used in improvement the efficiency of selection in plant breeding by marker-assisted selection (MAS). MAS is a powerful alternative to facilitate new gene deployment and gene pyramiding for quick release of rust-resistant cultivars. An approach called "genomic selection" and based on the widespread conventional selection with the use of information of the molecular markers will facilitate breeding programmes by providing effective achievement of biotic stress resistance reducing in mean time generation interval and investments in ecological-friendly crop production is reviewed.
Strategies for Wheat Stripe Rust Pathogenicity Identified by Transcriptome Sequencing  [PDF]
Diana P. Garnica, Narayana M. Upadhyaya, Peter N. Dodds, John P. Rathjen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067150
Abstract: Stripe rust caused by the fungus Puccinia striiformis f.sp. tritici (Pst) is a major constraint to wheat production worldwide. The molecular events that underlie Pst pathogenicity are largely unknown. Like all rusts, Pst creates a specialized cellular structure within host cells called the haustorium to obtain nutrients from wheat, and to secrete pathogenicity factors called effector proteins. We purified Pst haustoria and used next-generation sequencing platforms to assemble the haustorial transcriptome as well as the transcriptome of germinated spores. 12,282 transcripts were assembled from 454-pyrosequencing data and used as reference for digital gene expression analysis to compare the germinated uredinospores and haustoria transcriptomes based on Illumina RNAseq data. More than 400 genes encoding secreted proteins which constitute candidate effectors were identified from the haustorial transcriptome, with two thirds of these up-regulated in this tissue compared to germinated spores. RT-PCR analysis confirmed the expression patterns of 94 effector candidates. The analysis also revealed that spores rely mainly on stored energy reserves for growth and development, while haustoria take up host nutrients for massive energy production for biosynthetic pathways and the ultimate production of spores. Together, these studies substantially increase our knowledge of potential Pst effectors and provide new insights into the pathogenic strategies of this important organism.
DEVELOPMENT OF A MOLECULAR MARKER FOR RUST RESISTANCE GENES Sr39 AND Lr35 IN WHEAT BREEDING LINES
Electronic Journal of Biotechnology , 1999,
Abstract: polymorphic dna bands were identified between a near iso-isogenic line of wheat carrying both stem (sr39) and leaf (lr35) rust resistance genes and the recurrent line thatcher (tc) which lacks these genes. both resistance genes are located on a translocated chromosomal segment derived from aegilops speltoides and thus are genetically linked. the primers used to generate polymorphic bands were 3'-anchored inter-simple sequence repeat primers which identified genomic microsatellites with a repeated motif of 3 nucleotides in length. the primers were used singly to amplify genomic segments which were flanked by inversely orientated, closely spaced, identical microsatellite sequences. one of the polymorphic bands, a 900 base pair band, was completely linked to the sr39 and lr35 rust resistance genes in the segregating population used in this study. after cloning and sequencing this polymorphic band, the inter-simple sequence repeat marker was converted to a sequence characterized amplified region marker by designing primer sets which amplify a single, easily resolved band from dna of plants with sr39/lr35 genes. this marker is present in six wheat lines carrying the sr39 and lr35 genes on the translocated chromosome segment from ae. speltoides. the marker has facilitated efforts to breed canada prairie spring and canada western extra strong lines with these rust resistance genes
Introgression of Chromosome 3Ns from Psathyrostachys huashanica into Wheat Specifying Resistance to Stripe Rust  [PDF]
Houyang Kang,Yi Wang,George Fedak,Wenguang Cao,Haiqin Zhang,Xing Fan,Lina Sha,Lili Xu,Youliang Zheng,Yonghong Zhou
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021802
Abstract: Wheat stripe rust is a destructive disease in the cool and humid wheat-growing areas of the world. Finding diverse sources of stripe rust resistance is critical for increasing genetic diversity of resistance for wheat breeding programs. Stripe rust resistance was identified in the alien species Psathyrostachys huashanica, and a wheat- P. huashanica amphiploid line (PHW-SA) with stripe rust resistance was reported previously. In this study, a P. huashanica 3Ns monosomic addition line (PW11) with superior resistance to stripe rust was developed, which was derived from the cross between PHW-SA and wheat J-11. We evaluated the alien introgressions PW11-2, PW11-5 and PW11-8 which were derived from line PW11 for reaction to new Pst race CYR32, and used molecular and cytogenetic tools to characterize these lines. The introgressions were remarkably resistant to CYR32, suggesting that the resistance to stripe rust of the introgressions thus was controlled by gene(s) located on P. huashanica chromosome 3Ns. All derived lines were cytologically stable in term of meiotic chromosome behavior. Two 3Ns chromosomes of P. huashanica were detected in the disomic addition line PW11-2. Chromosomes 1B of substitution line PW11-5 had been replaced by a pair of P. huashanica 3Ns chromosomes. In PW11-8, a small terminal segment from P. huashanica chromosome arm 3NsS was translocated to the terminal region of wheat chromosomes 3BL. Thus, this translocated chromosome is designated T3BL-3NsS. These conclusions were further confirmed by SSR analyses. Two 3Ns-specific markers Xgwm181 and Xgwm161 will be useful to rapidly identify and trace the translocated fragments. These introgressions, which had significant characteristics of resistance to stripe rust, could be utilized as novel germplasms for wheat breeding.
Heritable, De Novo Resistance to Leaf Rust and Other Novel Traits in Selfed Descendants of Wheat Responding to Inoculation with Wheat Streak Mosaic Virus  [PDF]
Dallas L. Seifers, Steve Haber, Terry J. Martin, Brent D. McCallum
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0086307
Abstract: Stable resistance to infection with Wheat streak mosaic virus (WSMV) can be evolved de novo in selfing bread wheat lines subjected to cycles of WSMV inoculation and selection of best-performing plants or tillers. To learn whether this phenomenon might be applied to evolve resistance de novo to pathogens unrelated to WSMV, we examined the responses to leaf rust of succeeding generations of the rust- and WSMV-susceptible cultivar ‘Lakin’ following WSMV inoculation and derived rust-resistant sublines. After three cycles of the iterative protocol five plants, in contrast to all others, expressed resistance to leaf and stripe rust. A subset of descendant sublines of one of these, ‘R1’, heritably and uniformly expressed the new trait of resistance to leaf rust. Such sublines, into which no genes from a known source of resistance had been introgressed, conferred resistance to progeny of crosses with susceptible parents. The F1 populations produced from crosses between, respectively, susceptible and resistant ‘Lakin’ sublines 4-3-3 and 4-12-3 were not all uniform in their response to seedling inoculation with race TDBG. In seedling tests against TDBG and MKPS races the F2s from F1 populations that were uniformly resistant had 3:1 ratios of resistant to susceptible individuals but the F2s from susceptible F1 progenitors were uniformly susceptible. True-breeding lines derived from resistant individuals in F2 populations were resistant to natural stripe and leaf rust inoculum in the field, while the ‘Lakin’ progenitor was susceptible. The next generation of six of the ‘Lakin’-derived lines exhibited moderate to strong de novo resistance to stem rust races TPMK, QFCS and RKQQ in seedling tests while the ‘Lakin’ progenitor was susceptible. These apparently epigenetic effects in response to virus infection may help researchers fashion a new tool that expands the range of genetic resources already available in adapted germplasm.
Development of RAPD based markers for wheat rust resistance gene cluster (Lr37-Sr38-Yr17) derived from Triticum ventricosum L.
S Mumtaz, IA Khan, S Ali, B Zeb, A Iqbal, Z Shah, ZA Swati
African Journal of Biotechnology , 2009,
Abstract: Rust diseases are the major cause of low yield of wheat in Pakistan. Wheat breeders all over the world as well as in Pakistan are deriving rust resistance genes from alien species like Triticum ventricosum and introducing them in common wheat (Triticum aestivum). One such example is the introgression of rust resistance gene cluster Lr37-Sr38-Yr17 derived from T. ventricosum chromosome 2NS into the common wheat. A basic prerequisite to introduce alien rust resistance gene (like those present on 2NS segment) in locally adapted varieties is availability of a suitable marker system which can be used to keep track of presence of newly added gene in the old background. In this present study, one hundred and fifty Randomly Amplified Polymorphic DNA (RAPD) primers were used to detect polymorphism between two near isogenic lines NILs (Anza and Anza+2NS) of wheat and to develop RAPD based molecular markers for rust resistance gene cluster derived from T. ventricosum. Polymerase chain reactions were carried out using standard protocols. All the amplification products were in the range of 250 to 1000 bp. Thirteen molecular markers (RAPDs) out of a total of 150 (approximately 8.6%) were developed for rust resistance gene cluster Lr37-Sr38-Yr17 and recommendations have been made to utilize these markers in Pakistani wheat breeding programs aimed at establishing rust resistant germplasm.
Adult plant resistance in some Indian wheat genotypes and postulation of leaf rust resistance genes  [cached]
S.C. BHARDWAJ*, M. PRASHAR, S.K. JAIN, SUBODH KUMAR and D. DATTA
Indian Phytopathology , 2011,
Abstract: Advanced breeding lines and released/identified varieties of wheat were screened against different pathotypes of Puccinia triticina for leaf rust resistance both at seedling as well as adult plant stage in controlled polythene house conditions. Different combinations of seven resistance genes , viz. Lr1, Lr3, Lr10, Lr13, Lr23, Lr26 and Lr34 were characterized by applying the gene matching technique in 39 wheat lines that showed race-specific adult plant resistance (APR) to one and/or the other pathotypes. APR of both hypersensitive and non-hypersensitive types was observed. Varieties GW 322 ( Lr13+) and NIAW 34 ( Lr13+ 34+) showed APR to the three most pathogenic and virulent pathotypes 1R5 (12-2), 121R63-1(77-5) and 21R55(104-2). Twenty-one wheat lines/varieties showed APR to only two pathotypes. The remaining 16 lines showed APR to only one of the three pathotypes. Such race-specific adult plant resistance would be useful in breeding for leaf rust resistance. The seedling and adult plant resistance of these lines can be useful in increasing genetic diversity and avoiding leaf rust epiphytotics on wheat.
Accumulations of genes for durable resistance to wheat leaf rust pathogen  [PDF]
Bo?kovi? Jelena,Bo?kovi? M.,Priji? ?eljana
Journal of Agricultural Sciences , 2008, DOI: 10.2298/jas0803163b
Abstract: The individual use of single race-specific resistance genes with major phenotypic effects has rarely provided lasting resistance. However, breeding and combining or pyramiding of resistance genes into individual cultivars has had considerable success, particularly in situation where the pathogen does not reproduce sexually, as in the case of wheat leaf rust pathogen. Within international leaf rust of wheat investigations it was necessary, to create by breeding new resistant wheat lines to Puccinia recondita tritici for differentiation of pathogen population, as well as for sources of resistance in European-Mediterranean regions. In the beginning 18 donors of resistance had been selected after an extensive screening test of several International Rust Nurseries, to be crosses with recur- rent parents varieties Princ and Starke. These tests proved that in those lines were present new resistant genes. Eighth genetically different hybrids of the first back-cross had been selected and tested in the seedling stage with three international pathogen cultures (YU-13-19-1; H-13-9-1 and C2-13-Ar-3). Considerable influence of recurrent parent to the number of resistant genes in donors used was demonstrated. On the other side, it was established considerable influence of the pathogen culture to the number of resistant genes in donors used. The same crossing combinations tested with one pathogen culture results in presence of two resistance genes, but with another culture three or one resistant gene. In order to enhancement resistance and pyramiding genes in these hybrids, eight selected the most interesting lines have been crossed with only effective isogenic containing the strong genes Lr9, Lr19 and Lr24.The genetic analysis of twenty two crossing combinations have been realized by testing with three pathotypes of Puccinia recondita tritici ( Bg.s. 12/89; Is.w 8/89 and Chl.w. 14/89). On the base of different segregation ratios of all crossing combinations it was proved that no one of the resistant donors contained the strong resistant genes used. It means that our hybrid lines contained resistant genes from the donors and in addition three strong resistant genes Lr9, Lr19 and Lr24.
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