Genetic control of effective juvenile resistance to leaf rust in collection samples of Triticum aestivum L.

Of 153 samples reported to be resistant to leaf rust (Puccinia recondita Rob. ex. Desm.), only 70 were not affected by a complex P. recondita population. According to phytopathological tests (inoculation with test clones), 14 samples possessed the Lr19 gene; 36, the Lr24 gene; 1, the Lr41 gene; and 19 presumably had the Lr9 gene. The presence of these genes for resistance was confirmed by hybridological analysis for 26 samples. Of 28 samples reported to carry new effective genes for resistance other than the known genes, 23 were susceptible to the P. recondita population. In four of the other five samples, resistance proved to be controlled by known genes. Possible causes of false identification of new effective genes for leaf rust resistance in wheat are discussed.     

Leaf rust resistance genes of wheat: identification in cultivars and resistance sources

Thirty-seven wheat cultivars originating from seven European countries were examined by using sequence tagged site (STS) markers for seven Lr (leaf rust = brown rust) resistance genes against the fungal pathogen of wheat Puccinia recondita f. sp. tritici (Lr9, Lr10, Lr19, Lr24, Lr26 and Lr37). Additionally, 22 accessions with various Lr genes from two germplasm collections were tested. A Scar (sequence-characterized amplified region) marker for Lr24 and a CAPS (Cleaved Amplified Polymorphic Sequence) marker for Lr47 were also used to identify those genes in the wheat accessions. Each marker amplified one specific DNA fragment. Three Lr gene markers were identified in wheat cultivars (Lr10, Lr26 and Lr37). Another four markers (Lr9, Lr19, Lr24 and Lr47) were found in breeding lines carrying leaf rust resistance genes. The results were compared with leaf rust resistance gene postulations made in previous studies, based on multipathotype testing. Markers for Lr10, Lr26 and Lr37 may be useful in marker-assisted breeding.     

Genetic studies of leaf and stem rust resistance in six accessions of Triticum turgidum var. dicoccoides.

Six accessions of Triticum turgidum var. dicoccoides L. (4x, AABB) of diverse origin were tested with 10 races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and 10 races of stem rust (P. graminis f.sp. tritici Eriks. &Henn.). Their infection type patterns were all different from those of lines carrying the Lr or Sr genes on the A or B genome chromosomes with the same races. The unique reaction patterns are probably controlled by genes for leaf rust or stem rust resistance that have not been previously identified. The six dicoccoides accessions were crossed with leaf rust susceptible RL6089 durum wheat and stem rust susceptible 'Kubanka' durum wheat to determine the inheritance of resistance. They were also crossed in diallel to see whether they carried common genes. Seedlings of F1, F2, and BC1F2 generations from the crosses of the dicoccoides accessions with RL6089 were tested with leaf rust race 15 and those from the crosses with 'Kubanka' were tested with stem rust race 15B-1. The F2 populations from the diallel crosses were tested with both races. The data from the crosses with the susceptible durum wheats showed that resistance to leaf rust race 15 and stem rust race 15B-1 in each of the six dicoccoides accessions is conferred by a single dominant or partially dominant gene. In the diallel crosses, the dominance of resistance appeared to be affected by different genetic backgrounds. With one exception, the accessions carry different resistance genes: CI7181 and PI 197483 carry a common gene for resistance to leaf rust race 15. Thus, wild emmer wheat has considerable genetic diversity for rust resistance and is a promising source of new rust resistance genes for cultivated wheats.     

Marker-assisted selection for leaf rust resistance genes Lr19 and Lr24 in wheat (Triticum aestivum L.)

Leaf rust caused by Puccinia recondita f.sp. tritici is a wheat disease of worldwide importance. Wheat genotypes known to carry specific rust resistance genes and segregating lines that originated from various cross combinations and derived from distinct F2 lineage, so as to represent a diverse genetic background, were included in the present study for validation of molecular markers for Lr19 and Lr24. STS markers detected the presence of the leaf rust resistance gene Lr19 in a Thatcher NIL (Tc*Lrl9) and Inia66//CMH81A575 and of the gene Lr24 in the genotypes Arkan, Blue Boy II, Agent and CI 17907. Validation of molecular markers for Lr19 and Lr24 in parental lines, followed by successful detection of these genes in F3 lines from various cross combinations, was carried out. The molecular test corresponded well with the host-pathogen interaction test response of these lines.     

Phytopathological and molecular genetic identification of leaf rust resistance genes in common wheat accessions with alien genetic material

Leaf rust resistance genes were sought in 23 resistant common wheat accessions with alien genetic material of Aegilops speltoides, Ae. triuncialis, and Triticum kiharae from the Arsenal collection. The genes were identified by common phytopathological tests and PCR analysis with STS markers linked with the known Lr genes. None of the methods identified the resistance genes in two accessions. In the other accessions, the combination of the two methods broadened the spectrum of detectable genes and, in some cases, allowed double verification of the presence of a resistance gene. Most accessions proved to contain several leaf rust resistance genes, combining juvenile and adult plant ones. The accessions were found to contain gene combinations that ensured field resistance (Lr13 + Lr10 and Lr12 + Lr34) and immunity under the conditions of the Non-Chernozem region. Accessions with alien genetic material contained a unique combination of five or six resistance genes. Since the accessions were rich in leaf rust resistance genes, including effective ones, and carried rare combinations of these genes, they were proposed as donors to be universally employed in breeding for immunity in all regions of Russia.     

Molecular and phenotypic characterization of seedling and adult plant leaf rust resistance in a world wheat collection

Genetic resistance is the most effective approach to managing wheat leaf rust. The aim of this study was to characterize seedling and adult plant leaf rust resistance of a world wheat collection. Using controlled inoculation with ten races of Puccinia triticina, 14 seedling resistance genes were determined or postulated to be present in the collection. Lr1, Lr3, Lr10 and Lr20 were the most prevalent genes around the world while Lr9, Lr14b, Lr3ka and/or Lr30 and Lr26 were rare. To confirm some gene postulations, the collection was screened with gene-specific molecular markers for Lr1, Lr10, Lr21 and Lr34. Although possessing the Lr1 and/or Lr10 gene-specific marker, 51 accessions showed unexpected high infection types to P. triticina race BBBD. The collection was tested in the field, where rust resistance ranged from nearly immune or highly resistant with severity of 1 % and resistant host response to highly susceptible with severity of 84 % and susceptible host response. The majority of the accessions possessing the adult plant resistance (APR) gene Lr34 had a maximum rust severity of 0–35 %, similar to or better than accession RL6058, a Thatcher-Lr34 near-isogenic line. Many accessions displayed an immune response or a high level of resistance under field conditions, likely as a result of synergy between APR genes or between APR and seedling resistance genes. However, accessions with three or more seedling resistance genes had an overall lower field severity than those with two or fewer. Immune or highly resistant accessions are potential sources for improvement of leaf rust resistance. In addition, some lines were postulated to have known but unidentified genes/alleles or novel genes, also constituting potentially important sources of novel resistance.     

Phytopathological and molecular genetic identification of brown rust resistance genes in common wheat accessions with alien genetic material

Brown rust resistance genes were sought in 23 resistant common wheat accessions with alien genetic material of Aegilops speltoides, Ae. triuncialis, and Triticum kiharae from the Arsenal collection. The genes were identified by common phytopathological tests and PCR analysis with STS markers directed to the known Lr genes. None of the methods identified the resistance genes in two accessions. In the other accessions, the combination of the two methods broadened the spectrum of detectable genes and, in some cases, allowed double verification of the presence of a resistance gene. Most accessions proved to contain several brown rust resistance genes, combining juvenile and adult plant ones. The accessions were found to contain gene combinations that ensured field resistance and immunity under the conditions of the Non-Chernozem region (Lr13 + Lr10 and Lr12 + Lr34). Accessions with alien genetic material contained a unique combination of five or six resistance genes. Since the accessions were rich in brown rust resistance genes, including effective ones, and carried rare combinations of these genes, they were proposed as donors to be universally employed in breeding for immunity in all regions of Russia.     

Inheritance of leaf rust and stem rust resistance in 'Roblin' wheat.

The Canadian common wheat (Triticum aestivum L.) cultivar 'Roblin' is resistant to both leaf rust (Puccinia recondita Rob. ex. Desm.) and stem rust (Puccinia graminis Pers. f. sp. tritici Eriks. and E. Henn.). To study the genetics of this resistance, 'Roblin' was crossed with 'Thatcher', a leaf rust susceptible cultivar, and RL6071, a stem rust susceptible line. A set of F6 random lines was developed from each cross. The random lines and the parents were grown in a field rust nursery artificially inoculated with a mixture of P. recondita and P. graminis isolates and scored for rust reaction. The same material was tested with specific races of leaf rust and stem rust. These data indicated that 'Roblin' has Lr1, Lr10, Lr13, and Lr34 for resistance to P. recondita and Sr5, Sr9b, Sr11, and possibly Sr7a and Sr12 for resistance to P. graminis. In a 'Thatcher' background, the presence of Lr34 contributes to improve stem rust resistance, which appears also to occur in 'Roblin'.     

Molecular markers for leaf rust resistance genes in wheat

Over 100 genes of resistance to rust fungi: Puccinia recondita f. sp. tritici, (47 Lr - leaf rust genes), P. striiformis (18 Yr - yellow rust genes) and P. graminis f. sp. tritici (41 Sr - stripe rust genes) have been identified in wheat (Triticum aestivum L.) and its wild relatives according to recent papers. Sixteen Lr resistance genes have been mapped using restriction fragments length polymorphism (RFLP) markers on wheat chromosomes. More than ten Lr genes can be identified in breeding materials by sequence tagged site (STS) specific markers. Gene Lrk 10, closely linked to gene Lr 10, has been cloned and its function recognized. Available markers are presented in this review. The STS, cleaved amplified polymorphic sequence (CAPS) and sequence characterized amplified regions (SCAR) markers found in the literature should be verified using Triticum spp. with different genetic background. Simple sequence repeats (SSR) markers for Lr resistance genes are now also available.     

小麦叶锈病抗性基因在山西的有效性研究

采自山西省各地的小麦叶锈菌菌株分别接种在含有已知抗叶锈病基因的小麦近等基因系(或单基因系)上,测定其毒性频率,根据已知抗病基因对叶锈菌群体的抗性程度,对其进行抗性效能的评价。结果表明：抗性基因Lr9、Lr19、Lr24、Lr38的毒性频率较低,分别为23．08％、16．03％、12．82％和1．92％,为山西省小麦叶锈菌的有效抗病基因。在发现的诸多毒性类型中,THT、THK、PHT、TRT的出现频率居前四位,分别为19．23％、8．97％、7．05％、5．77％,为山西省目前小麦叶锈菌群体中的优势毒性类型。     

河南省16个主栽小麦品种抗叶锈基因分析

为了明确河南省小麦品种的抗叶锈性及抗叶锈基因的分布,为小麦品种推广与合理布局、叶锈病防治及抗病育种提供依据,本研究利用2015年采自河南省的5个小麦叶锈菌流行小种混合菌株,对近几年河南省16个主栽小麦品种进行了苗期抗性鉴定,然后选用12个小麦叶锈菌生理小种对这些品种进行苗期基因推导,同时利用与24个小麦抗叶锈基因紧密连锁(或共分离)的30个分子标记对该16个品种进行了抗叶锈基因分子检测。结果显示,供试品种苗期对小麦叶锈菌混合流行小种均表现高度感病;基因推导与分子检测结果表明,供试品种可能含有Lr1、Lr16、Lr26和Lr30这4个抗叶锈基因,其中先麦8号含有Lr1和Lr26;郑麦366和郑麦9023含有Lr1;西农979和怀川916含有Lr16;中麦895、偃展4110、郑麦7698、平安8号、众麦1号、周麦16、衡观35和矮抗58含有Lr26;周麦22中含有Lr26,还可能含有Lr1和Lr30;豫麦49-198和洛麦23可能含有本研究中检测以外的其他抗叶锈基因。因此,河南省主栽小麦品种的抗叶锈基因丰富度较低,今后育种工作应注重引入其他抗叶锈性基因,提高抗叶锈性,有效控制小麦叶锈病。     

Resistance of spring wheat cultivars and lines to leaf rust

Spring wheat nursery accessions, including 18 spring wheat lines derived in CIMMYT, Mexico, and 12 spring wheat cultivars bred in Poland, along with cultivars Frontana and Sumai 3 as resistant controls, were examined for resistance to leaf rust under field conditions. Multipathotype tests with 16 different pathogen isolates were performed for postulation of Lr genes in Polish cultivars. Besides, STS markers for resistance genes Lr1, Lr9, Lr10, Lr24, Lr28, Lr37 were analysed in the studied cultivars and lines with Thatcher near-isogenic lines as positive controls. All Polish cultivars appeared to be susceptible to leaf rust. Ten of the CIMMYT nursery lines (IPG-SW: #7, 11, 14, 21, 22, 23, 27, 29, 30, 32) and cv. Frontana were resistant in the same environment and can be sources of resistance genes. Marker for the Lr10 gene was identified in 6 accessions (IPG-SW #14, 22, 23, 29, 30, 32) exhibiting resistance to leaf rust, whereas markers for Lr1 and Lr28 genes were observed in all the examined accessions. STS markers for Lr9, Lr24 and Lr37 genes were not identified in the investigated accessions.     

Molecular mapping of leaf rust resistance gene LrNJ97 in Chinese wheat line Neijiang 977671

Neijiang 977671 and 19 near-isogenic lines with known leaf rust resistance genes were inoculated with 12 pathotypes of Puccinia triticina for postulation of leaf rust resistance genes effective at the seedling stage. The reaction pattern of Neijiang 977671 differed from those of the lines with known leaf rust resistance genes used in the test, indicating that Neijiang 977671 may carry a new leaf rust resistance gene(s). With the objective of identifying and mapping the new gene for resistance to leaf rust, F₁ and F₂ plants, and F_2:3 families, from Neijiang 977671 × Zhengzhou 5389 (susceptible) were inoculated with Chinese P. triticina pathotype FHNQ in the greenhouse. Results from the F₂ and F_2:3 populations indicated that a single dominant gene, temporarily designated LrNJ97, conferred resistance. In order to identify other possible genes in Neijiang 977671 other eight P. triticina pathotypes avirulent on Neijiang 977671 were used to inoculate 25 F_2:3 families. The results showed that at least three leaf rust resistance genes were deduced in Neijiang 977671. Bulked segregant analysis was performed on equal amounts of genomic DNA from 20 resistant and 20 susceptible F₂ plants. SSR markers polymorphic between the resistant and susceptible bulks were used to analyze the F_2:3 families. LrNJ97 was linked to five SSR loci on chromosome 2BL. The two closest flanking SSR loci were Xwmc317 and Xbarc159 at genetic distances of 4.2 and 2.2 cM, respectively. At present two designated genes (Lr50 and Lr58) are located on chromosome 2BL. In the seedling tests, the reaction pattern of LrNJ97 was different from that of Lr50. Lr50 and Lr58 were derived from T. armeniacum and Ae. triuncialis, respectively, whereas according to the pedigree of Neijiang 977671 LrNJ97 is from common wheat. Although seeds of lines with Lr58 were not available, it was concluded that LrNJ97 is likely to be a new leaf rust resistance gene.     

山东省12个主栽小麦品种(系)抗叶锈性分析

本研究旨在明确山东省12个小麦主栽品种(系)抗叶锈性及抗叶锈基因,为小麦品种推广与合理布局、叶锈病防治及抗病育种提供依据。利用2015年采自山东省的5个小麦叶锈菌流行小种的混合小种对这些材料进行苗期抗性鉴定,然后选用15个小麦叶锈菌生理小种对这些品种(系)进行苗期基因推导,并利用与24个小麦抗叶锈基因紧密连锁(或共分离)的30个分子标记对其进行抗叶锈基因分子检测。结果显示,山东省12个主栽小麦品种(系)苗期对该省2015年的5个小麦叶锈菌混合流行小种均表现高度感病。通过基因推导与分子检测发现,济南17含有Lr16,矮抗58和山农20含有Lr26,其余济麦系列、烟农系列、良星系列等9个品种(系)均未检测到所供试标记片段。此外,本研究还对山东省3个非主栽品种进行了检测,结果发现,中麦175含有抗叶锈基因Lr1和Lr37,含有成株抗性基因;皖麦38只检测到Lr26,济麦20未检测到所供试标记片段。综合以上结果,山东省主栽小麦品种(系)所含抗叶锈基因丰富度较低,尤其不含有对我国小麦叶锈菌流行小种有效的抗锈基因,应该引起高度重视,今后育种工作应注重引入其他抗叶锈基因,提高抗叶锈性。     

An interchromosomal reciprocal translocation in wheat involving leaf rust resistance gene Lr34.

'Thatcher' backcross lines RL6058 and RL6077 have adult-plant leaf rust resistance and were believed to have Lr34. However, genetic analysis revealed that the genes in the two lines were independent of each other. Previous work demonstrated that Lr34 is located on chromosome 7D. The leaf rust resistance gene in RL6058 must be on chromosome 7DS because no recombinants were observed between it and gene Lr29, known to be on chromosome 7DS. It was also linked with Rc3 (30.25 +/- 2.88%), a gene for purple coleoptile on chromosome 7DS. It was independent of Lr19 and NS1 (nonsuppressor mutant), which are located on 7DL. The leaf rust resistance gene in RL6077 was independent of genes Lr19 and Lr29. The presence of quadrivalents in pollen mother cells of the RL6058/RL6077 hybrid indicates that the Lr34 gene in RL6077 may have been translocated onto another chromosome. Lr34 from RL6058 and RL6077 may have been combined in four F3 lines derived from their intercross.     

15个小麦农家品种抗叶锈基因分析

本研究旨在明确小麦农家品种中可能含有的抗叶锈病基因,为抗源的选择和利用提供理论依据。以15个小麦农家品种、感病对照品种郑州5389和36个含有已知抗叶锈病基因的载体品种为材料,苗期接种19个具有鉴别力的叶锈菌生理小种进行基因推导,同时利用12个与抗叶锈病基因紧密连锁的分子标记进行分析。为明确其成株期抗性,分别于2016-2017年和2017-2018年在河北保定对小麦农家品种、感病对照品种郑州5389与慢锈品种SAAR进行田间接种,调查并记录田间严重度及普遍率。基因推导和分子标记检测结果显示,在15个小麦农家品种中共检测到7个抗叶锈病基因,其中部分品种还有多个抗性基因,如红狗豆含有Lr1和Lr46;黄花麦含有Lr13和Lr34;大白麦含有Lr14b和Lr26;洋麦含有Lr37和Lr46;成都光头含有Lr34和Lr46;墨脱麦和西山扁穗含有Lr26和Lr46。部分品种含有1个成株期慢叶锈病抗性基因,如同家坝小麦、武都白茧儿、边巴春麦-6、白花麦含有Lr34;红抢麦、白扁穗和白火麦含有Lr46。这些携带有效抗叶锈病基因的农家品种,可为小麦抗叶锈病育种提供抗源。     

8个小麦育种亲本抗叶锈基因分析

选取19个小麦叶锈菌生理小种对8个小麦育种亲本进行成株期和苗期抗叶锈病鉴定及基因推导,同时利用与24个抗叶锈基因紧密连锁或共分离的31个分子标记进行分子检测。推测出L83#-5与L83#-6含有Lr1,可能含有Lr2c和Lr42;L/PL2003-1含有Lr1,可能含有Lr2c、Lr28和Lr42;贵农13号可能含有Lr28;92R137可能含有Lr2c和Lr28;L201含有Lr1,可能含有Lr2c、Lr16和Lr28;TM可能含有Lr41和其他抗叶锈基因。研究结果表明,测试的8个小麦育种亲本中TM的抗叶锈性最好,具有很好的抗叶锈病应用潜力,可作为小麦抗叶锈病育种的重要抗源。     

Application of STS markers for leaf rust resistance genes in near-isogenic lines of spring wheat cv. Thatcher

Sequence tagged site (STS) markers for eight resistance genes against Puccinia recondita f. sp. tritici were used to screen a set of near-isogenic lines of wheat cv. Thatcher containing in total 40 different Lr genes and their alleles. Polymerase chain reaction (PCR) analysis was carried out by using STS, SCAR and CAPS primers specific for the leaf rust resistance genes Lr1, Lr9, Lr10, Lr19, Lr24, Lr28, Lr37 and Lr47. The STS, CAPS and SCAR markers linked to resistance genes Lr9, Lr10, Lr19, Lr24, Lr37 and Lr47 were found to be reliable in diverse genetic backgrounds. The amplification product of the Lr1 gene marker was detected in the susceptible cv. Thatcher and in all of the near-isogenic lines examined except Lr2a, Lr2b, Lr2c and Lr19. The sequence analysis of PCR products amplified in lines Lr1, Lr10, Lr28 and in cv. Thatcher indicated that the near-isogenic lines and cv. Thatcher contained in the targeted chromosome region an allele that differed from the original alleles corresponding to Lr1/6*Thatcher (TLR621) and susceptible Thatcher (TH621). The amplification product specific to the STS marker of the Lr1 gene was amplified in almost all Thatcher near-isogenic lines and in cv. Thatcher because their alleles possessed primer sequences identical to the original allele TLR621. The marker for the Lr28 resistance gene was identified in line Lr28, carrying gene Lr28, and in 21 other near-isogenic lines. The sequencing of PCR products specific to Lr28 and generated in lines Lr1, Lr10 and Lr28 indicated that the lines Lr1, Lr10 and Lr28 are heterozygous in this region.     

Effect of gene Lr34 in the enhancement of resistance to leaf rust of wheat

Summary Leaf rust resistance gene Lr34 is present in many wheat cultivars throughout the world that have shown durable resistance to leaf rust. Fourteen pair-wise combinations of Lr34 and seedling leaf rust resistance genes were developed by intercrossing near isogenic Thatcher lines. In both seedling and adult plant tests homozygous paired combinations of specific resistance genes with Lr34 had enhanced resistance relative to either parent to different numbers of isolates that were avirulent to the additional resistance genes. The TcLr34, 18 line also expressed enhanced resistance to specific isolates virulent to Lr18 in seedling and adult plant stages. In rust nursery tests, homozygous lines were more resistant than either parent, if the additional leaf rust gene conditioned an effective of resistance when present singly. The ability of Lr34 to interact with other genes conditioning effective resistance may contribute to the durability of leaf rust resistance in cultivars with Lr34. Contribution 1453 Agriculture Canada     

Genetic Characterization of Rye Accessions with Regard to Leaf Rust Resistance

The genetic control of leaf rust resistance has been investigated by test crosses and the test-clone method in the rye accessions Malysh 72-2, Chulpan 3, Immunnaya 4, Yaroslavna 3, Lovashpatonae 2, Gotor 2, Talovskaya 12-2, Braunrostresisten 2, Orlovskaya 9-2, 3098/18, and 4001/10. It has been found that this trait is controlled by a set of nonidentical oligogenes. Dominant geneLr6 controls leaf rust resistance in Chulpan 3 and Immunnaya 4;Lr5, in Malysh 72-2; and Lr-c, in Yaroslavna 3. Test crosses have shown that genesLr-a and Lr-bdiffer from the genes determining the resistance in Gotor 2 and Braunrostresisten 2. In German accessions 4001/10 and 3098/18, the resistance to the Petersburg population of the pathogen is controlled by nonallelic genes Lr-a andLr-b. It has been found that gene Lr-b is not identical to the resistance gene of Lovashpatonae 2, and Lr-a is not identical to Lr-c.In all accessions, resistance to the leaf rust population is controlled by dominant genes from the stage of seedlings till maturity. Highly efficient Lr genes are present in the accessions Malysh 72-2, Chulpan 3, Immunnaya 4, Yaroslavna 3, Lovashpatonae 2, Gotor 2, Talovskaya 12-2, 3098/18, and 4001/10. In addition to the oligogenes, most accessions possess genes efficiently controlling particular clones of the pathogen.