scholarly journals Population genomics, linkage disequilibrium and association mapping of stripe rust resistance genes in wild emmer wheat, Triticum turgidum ssp. dicoccoides

Author(s):  
Hanan Sela ◽  
Eduard Akhunov ◽  
Brian J. Steffenson

The primary goals of this project were: (1) development of a genetically characterized association panel of wild emmer for high resolution analysis of the genetic basis of complex traits; (2) characterization and mapping of genes and QTL for seedling and adult plant resistance to stripe rust in wild emmer populations; (3) characterization of LD patterns along wild emmer chromosomes; (4) elucidation of the multi-locus genetic structure of wild emmer populations and its correlation with geo-climatic variables at the collection sites. Introduction In recent years, Stripe (yellow) rust (Yr) caused by Pucciniastriiformis f. sp. tritici(PST) has become a major threat to wheat crops in many parts of the world. New races have overcome most of the known resistances. It is essential, therefore, that the search for new genes will continue, followed by their mapping by molecular markers and introgression into the elite varieties by marker-assisted selection (MAS). The reservoir of genes for disease and pest resistance in wild emmer wheat (Triticumdicoccoides) is an important resource that must be made available to wheat breeders. The majority of resistance genes that were introgressed so far in cultivated wheat are resistance (R) genes. These genes, though confering near-immunity from the seedling stage, are often overcome by the pathogen in a short period after being deployed over vast production areas. On the other hand, adult-plant resistance (APR) is usually more durable since it is, in many cases, polygenic and confers partial resistance that may put less selective pressure on the pathogen. In this project, we have screened a collection of 480 wild emmer accessions originating from Israel for APR and seedling resistance to PST. Seedling resistance was tested against one Israeli and 3 North American PST isolates. APR was tested on accessions that did not have seedling resistance. The APR screen was conducted in two fields in Israel and in one field in the USA over 3 years for a total of 11 replicates. We have found about 20 accessions that have moderate stripe rust APR with infection type (IT<5), and about 20 additional accessions that have novel seedling resistance (IT<3). We have genotyped the collection using genotyping by sequencing (GBS) and the 90K SNP chip array. GBS yielded a total 341K SNP that were filtered to 150K informative SNP. The 90K assay resulted in 11K informative SNP. We have conducted a genome-wide association scan (GWAS) and found one significant locus on 6BL ( -log p >5). Two novel loci were found for seedling resistance. Further investigation of the 6BL locus and the effect of Yr36 showed that the 6BL locus and the Yr36 have additive effect and that the presence of favorable alleles of both loci results in reduction of 2 grades in the IT score. To identify alleles conferring adaption to extreme climatic conditions, we have associated the patterns of genomic variation in wild emmer with historic climate data from the accessions’ collection sites. The analysis of population stratification revealed four genetically distinct groups of wild emmer accessions coinciding with their geographic distribution. Partitioning of genomic variance showed that geographic location and climate together explain 43% of SNPs among emmer accessions with 19% of SNPs affected by climatic factors. The top three bioclimatic factors driving SNP distribution were temperature seasonality, precipitation seasonality, and isothermality. Association mapping approaches revealed 57 SNPs associated with these bio-climatic variables. Out of 21 unique genomic regions controlling heading date variation, 10 (~50%) overlapped with SNPs showing significant association with at least one of the three bioclimatic variables. This result suggests that a substantial part of the genomic variation associated with local adaptation in wild emmer is driven by selection acting on loci regulating flowering. Conclusions: Wild emmer can serve as a good source for novel APR and seedling R genes for stripe rust resistance. APR for stripe rust is a complex trait conferred by several loci that may have an additive effect. GWAS is feasible in the wild emmer population, however, its detection power is limited. A panel of wild emmer tagged with more than 150K SNP is available for further GWAS of important traits. The insights gained by the bioclimatic-gentic associations should be taken into consideration when planning conservation strategies.  

Author(s):  
Pratima Sharma ◽  
Madhu Patial ◽  
Dharam Pal ◽  
S. C. Bhardwaj ◽  
Subodh . Kumar ◽  
...  

The present study was conducted to transfer multiple rust resistance in a popular but rust susceptible wheat cultivar HS295. Selected derivatives WBM3632 and WBM3635 have been developed from a cross, HS295*2/FLW20//HS295*2/ FLW13 using bulk-pedigree method of breeding. Advance line WBM3697 selected from a breeding line WBM3532 was named as HS661. This line was evaluated for seedling resistance to a wide array of rust pathotypes and found to possess resistance to all the three rusts. HS661 was also tested under field conditions and showed adult plant resistance to leaf rust (AC1=0.6), stem rust (ACI=2.7) and strpe rust (AC1=3.8). Among 34 F3 lines, 28 were tested positive for SSR marker Xwmc221 indicating the presence of Lr19/Sr25. Out of 14 selected F4 lines from F3, nine were homozygous positive for Lr19/Sr25. The advanced breeding lines viz., WBM3632 (WBM3697) and WBM3635 were also positive for Lr19/Sr25 with SCAR marker SCS265512. SSR marker Xgwm1 producing 215 bp band in Avst-15, FLW13 and HS661 confirmed the presence of Yr15 . Agronomically, HS661 was comparable with recipient variety HS295 and superior to a standard check HS490 under late sown restricted irrigation production conditions of NHZ. HS661 may serve as a potential donor for creating new usable variability against all the three rusts.


Plant Disease ◽  
2020 ◽  
Author(s):  
Yu Wu ◽  
Yuqi Wang ◽  
Fangjie Yao ◽  
Li Long ◽  
Jing Li ◽  
...  

Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases of wheat in the world. Chinese wheat landrace ‘Guangtoumai’ (GTM) exhibited a high-level resistance against predominant Pst races in China at the adult-plant stage. The objective of this research was to identify and map the major locus/loci for stripe rust resistance in GTM. A set of 212 recombinant inbred lines (RILs) was developed from a cross between GTM and Avocet S (AvS). The parents and RILs were evaluated in three field tests (2018, 2019, and 2020 at Chongzhou, Sichuan) with the currently predominant Pst races for final disease severity (FDS) and genotyped with the Wheat 55K SNP array to construct a genetic map with 1,031 SNP markers. A major locus, named QYr.GTM-5DL, was detected on chromosome 5DL in GTM. The locus was mapped in a 2.75 cM interval flanked by SNP markers AX-109855976 and AX-109453419, explaining up to 44.4% of the total phenotypic variation. Since no known Yr genes have been reported on chromosome 5DL, QYr.GTM-5DL is very likely a novel adult plant resistance (APR) locus. Haplotype analysis revealed that the resistance allele displayed enhanced levels of stripe rust resistance and is likely present in 5.3% of the 247 surveyed Chinese wheat landraces. The derived cleaved amplified polymorphic sequence (dCAPS) marker dCAPS-5722, converted from a SNP marker tightly linked to QYr.GTM-5DL with 0.3 cM, was validated on a subset of RILs and 48 commercial wheat cultivars developed in Sichuan. The results indicated that QYr.GTM-5DL with its linked dCAPS marker could be used in marker-assisted selection to improve stripe rust resistance in breeding programs, and this QTL will provide new and possibly durable resistance to stripe rust.


2010 ◽  
Vol 61 (12) ◽  
pp. 1036 ◽  
Author(s):  
J. Zhang ◽  
C. R. Wellings ◽  
R. A. McIntosh ◽  
R. F. Park

Seedling resistances to stem rust, leaf rust and stripe rust were evaluated in the 37th International Triticale Screening Nursery, distributed by the International Wheat and Maize Improvement Centre (CIMMYT) in 2005. In stem rust tests, 12 and 69 of a total of 81 entries were postulated to carry Sr27 and SrSatu, respectively. When compared with previous studies of CIMMYT triticale nurseries distributed from 1980 to 1986 and 1991 to 1993, the results suggest a lack of expansion in the diversity of stem rust resistance. A total of 62 of 64 entries were resistant to five leaf rust pathotypes. In stripe rust tests, ~93% of the lines were postulated to carry Yr9 alone or in combination with other genes. The absence of Lr26 in these entries indicated that Yr9 and Lr26 are not genetically associated in triticale. A high proportion of nursery entries (63%) were postulated to carry an uncharacterised gene, YrJackie. The 13 lines resistant to stripe rust and the 62 entries resistant to leaf rust represent potentially useful sources of seedling resistance in developing new triticale cultivars. Field rust tests are needed to verify if seedling susceptible entries also carry adult plant resistance.


2020 ◽  
Author(s):  
Yuqi Wang ◽  
Can Yu ◽  
Yukun Cheng ◽  
Fangjie Yao ◽  
Li Long ◽  
...  

Abstract Background: Stripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is a serious foliar disease of wheat. Identification of novel stripe rust resistance genes and cultivation of resistant varieties are considered to be the most effective approaches to control this disease. In this study, we evaluated the infection type (IT), disease severity (DS) and area under the disease progress curve (AUDPC) of 143 Chinese wheat landrace accessions for stripe rust resistance. Assessments were undertaken in five environments at the adult-plant stage with Pst mixture races under field conditions, in addition, IT was assessed at the seedling stage with two prevalent Pst races (CYR32 and CYR34) under controlled greenhouse conditions.Results: Seventeen accessions showed stable high-level resistance to stripe rust across all environments under field tests, while four accessions showed resistance to the Pst races CYR32 and CYR34 at the seedling stage. Combining phenotypic data from the field and greenhouse trials with 6404 markers covering the whole genome, we detected 17 quantitative trait loci (QTL) on 11 chromosomes for IT associated with seedling resistance and 15 QTL on seven chromosomes for IT, final disease severity (FDS) or AUDPC associated with adult-plant resistance. Four stable QTL detected on four chromosomes, which explained 9.99%–23.30% of the phenotypic variation, were simultaneously associated with seedling and adult-plant resistance. Integrating a linkage map of stripe rust resistance in wheat, 27 QTL overlapped with previously reported genes or QTL, while four and one QTL conferring seedling and adult-plant resistance respectively were mapped distantly from previously reported stripe rust resistance genes or QTL and may be novel resistance loci.Conclusions: Our results provided an integrated view of stripe rust resistance resources in a Chinese wheat landrace diversity panel from the southern autumn-sown spring wheat zone. The identified resistant accessions and resistance loci will be useful in the ongoing effort to develop new wheat cultivars with strong resistance to stripe rust.


2020 ◽  
Author(s):  
Yuqi Wang ◽  
Can Yu ◽  
Yukun Cheng ◽  
Fangjie Yao ◽  
Li Long ◽  
...  

Abstract Background: Stripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is a serious foliar disease of wheat. Identification of novel stripe rust resistance genes and cultivation of resistant varieties are considered to be the most effective approaches to control this disease. In this study, we evaluated the infection type (IT), disease severity (DS) and area under the disease progress curve (AUDPC) of 143 Chinese wheat landrace accessions for stripe rust resistance. Assessments were undertaken in five environments at the adult-plant stage with Pst mixture races under field conditions, in addition, IT was assessed at the seedling stage with two prevalent Pst races (CYR32 and CYR34) under controlled greenhouse conditions. Results: Seventeen accessions showed stable high-level resistance to stripe rust across all environments under field tests, while four accessions showed resistance to the Pst races CYR32 and CYR34 at the seedling stage. Combining phenotypic data from the field and greenhouse trials with 6404 markers covering the whole genome, we detected 17 quantitative trait loci (QTL) on 11 chromosomes for IT associated with seedling resistance and 15 QTL on seven chromosomes for IT, final disease severity (FDS) or AUDPC associated with adult-plant resistance. Four stable QTL detected on four chromosomes, which explained 9.99%–23.30% of the phenotypic variation, were simultaneously associated with seedling and adult-plant resistance. Integrating a linkage map of stripe rust resistance in wheat, 27 QTL overlapped with previously reported genes or QTL, while four and one QTL conferring seedling and adult-plant resistance respectively were mapped distantly from previously reported stripe rust resistance genes or QTL and may be novel resistance loci. Conclusions: Our results provided an integrated view of stripe rust resistance resources in a Chinese wheat landrace diversity panel from the southern autumn-sown spring wheat zone. The identified resistant accessions and resistance loci will be useful in the ongoing effort to develop new wheat cultivars with strong resistance to stripe rust.


2021 ◽  
Vol 12 ◽  
Author(s):  
Sandra Rollar ◽  
Manuel Geyer ◽  
Lorenz Hartl ◽  
Volker Mohler ◽  
Frank Ordon ◽  
...  

Stripe rust caused by the biotrophic fungus Puccinia striiformis Westend. is one of the most important diseases of wheat worldwide, causing high yield and quality losses. Growing resistant cultivars is the most efficient way to control stripe rust, both economically and ecologically. Known resistance genes are already present in numerous cultivars worldwide. However, their effectiveness is limited to certain races within a rust population and the emergence of stripe rust races being virulent against common resistance genes forces the demand for new sources of resistance. Multiparent advanced generation intercross (MAGIC) populations have proven to be a powerful tool to carry out genetic studies on economically important traits. In this study, interval mapping was performed to map quantitative trait loci (QTL) for stripe rust resistance in the Bavarian MAGIC wheat population, comprising 394 F6 : 8 recombinant inbred lines (RILs). Phenotypic evaluation of the RILs was carried out for adult plant resistance in field trials at three locations across three years and for seedling resistance in a growth chamber. In total, 21 QTL for stripe rust resistance corresponding to 13 distinct chromosomal regions were detected, of which two may represent putatively new QTL located on wheat chromosomes 3D and 7D.


2012 ◽  
Vol 63 (6) ◽  
pp. 539 ◽  
Author(s):  
M. A. Asad ◽  
B. Bai ◽  
C. X. Lan ◽  
J. Yan ◽  
X. C. Xia ◽  
...  

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a fungal disease that causes significant yield losses in many wheat-growing regions of the world. Previously, five quantitative trait loci (QTLs) for adult-plant resistance (APR) to stripe rust resistance were identified in Italian wheat cultivar Libellula. The objectives of this study were to map QTLs for APR to powdery mildew in 244 F2 : 3 lines of Libellula/Huixianhong, to analyse the stability of detected QTLs across environments, and to assess the association of these QTLs with stripe rust resistance. Powdery mildew response was evaluated for 2 years in Beijing and for 1 year in Anyang. The correlation between averaged maximum disease severity (MDS) and averaged area under disease progress curve (AUDPC) over 2 years in Beijing was 0.98, and heritabilities of MDS and AUDPC were 0.65 and 0.81, respectively, based on the mean values averaged across environments. SSR markers were used to screen the parents and mapping population. Five QTLs were identified by inclusive composite interval mapping, designated as QPm.caas-2DS, QPm.caas-4BL.1, QPm.caas-6BL.1, QPm.caas-6BL.2, and QPm.caas-7DS. Three QTLs (QPm.caas-2DS and QPm.caas-6BL.1, and QPm.caas-6BL.2) seem to be new resistance loci for powdery mildew. QTLs QPm.caas-2DS and QPm.caas-4BL.1 were identified at the same position as previously mapped QTLs for stripe rust resistance in Libellula. The QTL QPm.caas-7DS, derived from Libellula, coincided with the slow rusting and slow mildewing locus Lr34/Yr18/Pm38. These results and the identified markers could be useful for wheat breeders aiming for durable resistance to both powdery mildew and stripe rust.


2016 ◽  
Vol 106 (11) ◽  
pp. 1344-1351 ◽  
Author(s):  
K. Esvelt Klos ◽  
T. Gordon ◽  
P. Bregitzer ◽  
P. Hayes ◽  
X. M. Chen ◽  
...  

Quantitative trait loci (QTL) for barley stripe rust resistance were mapped in recombinant inbred lines (RIL) from a ‘Lenetah’ × ‘Grannelose Zweizeilige’ (GZ) cross. GZ is known for a major seedling resistance QTL on chromosome 4H but linked markers suitable for marker-assisted selection have not been developed. This study identified the 4H QTL (log of the likelihood [LOD] = 15.94 at 97.19 centimorgans [cM]), and additional QTL on chromosomes 4H and 6H (LOD = 5.39 at 72.7 cM and 4.24 at 34.46 cM, respectively). A QTL on chromosome 7H (LOD = 2.04 at 81.07 cM) was suggested. All resistance alleles were derived from GZ. Evaluations of adult plant response in Corvallis, OR in 2013 and 2015 provided evidence of QTL at the same positions. However, the minor QTL on 4H was not statistically significant in either location/year, while the 7H QTL was significant in both. The single-nucleotide polymorphism markers flanking the resistance QTL were validated in RIL from a ‘95SR316A’ × GZ cross for their ability to predict seedling resistance. In 95SR316A × GZ, 91 to 92% of RIL with GZ alleles at the major 4H QTL and at least one other were resistant to moderate in reaction. In these populations, at least two QTL were required to transfer the barley stripe rust resistance from GZ.


2005 ◽  
Vol 56 (6) ◽  
pp. 619 ◽  
Author(s):  
M. Imtiaz ◽  
M. G. Cromey ◽  
J. G. Hampton ◽  
F. C. Ogbonnaya

The New Zealand wheat (Triticum aestivum L.) cv. Karamu (same parentage as the US cv. Anza) was originally believed to carry gene Yr18, which provides adult plant resistance to stripe rust (Puccinia striiformis f. sp. tritici), in addition to the seedling resistance gene YrA. Following the detection of virulence to the stripe rust resistance gene YrA in 1995, much of the resistance of Karamu was eroded and the cultivar suffered from occasional severe stripe rust outbreaks. This meant that either one or more new races of Puccinia striiformis f. sp. tritici with virulence to Yr18 had developed, or that Yr18 conferred inadequate resistance under high disease pressure. Karamu was crossed with cv. Otane, which carries Yr18, and 140 double haploid (DH) lines obtained from the F1 progeny were evaluated for seedling and adult plant resistance under greenhouse and field conditions. Evaluation of F1 plants against stripe rust pathotype 106E139A+ revealed that the resistance was recessive and that none of the resistance genes present was effective at the seedling stage. Segregation in the DH lines at the adult plant stage indicated that the resistance measured through infection type in both the greenhouse and the field was based on 3 genes, 1 from Karamu and 2 from Otane. However, the resistance gene from Karamu did not contribute towards resistance measured through final disease severity, but acted additively with genes from Otane in providing slow-rusting resistance as expressed by lower values for area under the disease progress curve. It was concluded that Karamu does not have gene Yr18, but rather possesses a recessive minor gene, which explains its adult plant susceptibility under high disease pressure. However, this Karamu gene did interact with Otane resistance genes to provide increased resistance.


2020 ◽  
Author(s):  
Yuqi Wang ◽  
Can Yu ◽  
Yukun Cheng ◽  
Fangjie Yao ◽  
Li Long ◽  
...  

Abstract Background:Stripe rust, caused by the fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is a serious foliar disease of wheat. Identification of novel stripe-rust resistance genes and cultivation of resistant varieties are considered to be the most effective approaches to control this disease. In this study, we evaluated the infection type (IT), disease severity (DS) and area under the disease progress curve (AUDPC) of 143 Chinese wheat landrace accessions for stripe-rust resistance. Assessments were undertaken in five environments at the adult-plant stage with Pst mixture races under field conditions, in addition, IT was assessed at the seedling stage with two prevalent Pst races (CYR32 and CYR34) under controlled greenhouse conditions. Results:Seventeen accessions showed stable high-level resistance to stripe rust across all environments under field tests,while four accessions showed resistance to the Pst races CYR32 and CYR34 at the all-stage.Combining phenotypic data from the field and greenhouse trials with 6404 markers covering the whole genome, we detected 17quantitative trait locus(QTLs) on 11 chromosomes for IT associated with seedling resistance and 15 QTLs on seven chromosomes for IT, final disease severityor AUDPC associated with adult-plant resistance. Four stable QTLs detected on four chromosomes, which explained 9.99%–23.30% of the phenotypic variation, were simultaneously associated with seedling and adult-plant resistance. Integrating a linkage map of stripe-rust resistance in wheat, 29 QTLs overlapped with previously reported genes or QTLs, while two and oneQTLs conferring seedling and adult-plant resistancerespectively were mapped distantly from previously reported stripe rust resistance genes or QTLs and may be novel resistantloci. Conclusions:Our results provided an integrated view of stripe rust resistance resources in a Chinese wheat landrace diversity panel from the southern autumn-sown spring wheat zone.The identified resistant accessions and resistance loci will be useful in the ongoing effort to develop new wheat cultivars with strong resistance to stripe rust.


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