scholarly journals Genome-Wide Association Study Reveals Novel Genetic Loci for Quantitative Resistance to Septoria Tritici Blotch in Wheat (Triticum aestivum L.)

2021 ◽  
Vol 12 ◽  
Author(s):  
Tilahun Mekonnen ◽  
Clay H. Sneller ◽  
Teklehaimanot Haileselassie ◽  
Cathrine Ziyomo ◽  
Bekele G. Abeyo ◽  
...  
Keyword(s):  
Genome Wide Association Study ◽  
Agronomic Traits ◽  
Defense Responses ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Adult Plant ◽  
Putative Qtls ◽  
Association Panel ◽  
A Genome ◽  
Trait Associations

Septoria tritici blotch, caused by the fungus Zymoseptoria titici, poses serious and persistent challenges to wheat cultivation in Ethiopia and worldwide. Deploying resistant cultivars is a major component of controlling septoria tritici blotch (STB). Thus, the objective of this study was to elucidate the genomic architecture of STB resistance in an association panel of 178 bread wheat genotypes. The association panel was phenotyped for STB resistance, phenology, yield, and yield-related traits in three locations for 2 years. The panel was also genotyped for single nucleotide polymorphism (SNP) markers using the genotyping-by-sequencing (GBS) method, and a total of 7,776 polymorphic SNPs were used in the subsequent analyses. Marker-trait associations were also computed using a genome association and prediction integrated tool (GAPIT). The study then found that the broad-sense heritability for STB resistance ranged from 0.58 to 0.97 and 0.72 to 0.81 at the individual and across-environment levels, respectively, indicating the presence of STB resistance alleles in the association panel. Population structure and principal component analyses detected two sub-groups with greater degrees of admixture. A linkage disequilibrium (LD) analysis in 338,125 marker pairs also detected the existence of significant (p ≤ 0.01) linkage in 27.6% of the marker pairs. Specifically, in all chromosomes, the LD between SNPs declined within 2.26–105.62 Mbp, with an overall mean of 31.44 Mbp. Furthermore, the association analysis identified 53 loci that were significantly (false discovery rate, FDR, <0.05) associated with STB resistance, further pointing to 33 putative quantitative trait loci (QTLs). Most of these shared similar chromosomes with already published Septoria resistance genes, which were distributed across chromosomes 1B, 1D, 2A, 2B, 2D, 3A,3 B, 3D, 4A, 5A, 5B, 6A, 7A, 7B, and 7D. However, five of the putative QTLs identified on chromosomes 1A, 5D, and 6B appeared to be novel. Dissecting the detected loci on IWGSC RefSeq Annotation v2.1 revealed the existence of disease resistance-associated genes in the identified QTL regions that are involved in plant defense responses. These putative QTLs explained 2.7–13.2% of the total phenotypic variation. Seven of the QTLs (R2 = 2.7–10.8%) for STB resistance also co-localized with marker-trait associations (MTAs) for agronomic traits. Overall, this analysis reported on putative QTLs for adult plant resistance to STB and some important agronomic traits. The reported and novel QTLs have been identified previously, indicating the potential to improve STB resistance by pyramiding QTLs by marker-assisted selection.

scholarly journals Genome-Wide Association Study Reveals Genetic Architecture of Septoria Tritici Blotch Resistance in a Historic Landrace Collection

2021 ◽  
Author(s):  
Anik Dutta ◽  
Daniel Croll ◽  
Bruce A. McDonald ◽  
Simon G. Krattinger
Keyword(s):  
Genetic Diversity ◽  
Association Study ◽  
Genome Wide Association Study ◽  
Phenotypic Variability ◽  
Genome Wide Association ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Genome Wide ◽  
A Genome ◽  
Wheat Landraces

Abstract Septoria tritici blotch (STB), caused by the fungus Zymoseptoria tritici, is a major constraint in global wheat production. The lack of genetic diversity in modern elite wheat cultivars largely hinders the improvement of STB resistance. Wheat landraces are reservoirs of untapped genetic diversity, which can be exploited to find novel STB resistance genes or alleles. Here, we characterized 188 Swiss wheat landraces for resistance to STB using four Swiss Z. tritici isolates. We used a genome-wide association study (GWAS) to identify genetic variants associated with the amount of lesion and pycnidia production by the fungus. The majority of the landraces were highly resistant for both traits to the isolate 1E4, indicating a gene-for-gene relationship, while higher phenotypic variability was observed against other isolates. GWAS detected a significant SNP on chromosome 3A that was associated with both traits in the isolate 1E4. The resistance response against 1E4 was likely controlled by the Stb6 gene. Sanger sequencing revealed that the majority of these ~100-year-old landraces carry the Stb6 resistance allele. This indicates the importance of this gene in Switzerland during the early 1900s for disease control in the field. Our study demonstrates the importance of characterizing historic landrace collections for STB resistance to provide valuable information on resistance variability and contributing alleles. This will help breeders in the future to make decisions on integrating such germplasms in STB resistance breeding.

scholarly journals QTL Mapping of Seedling and Adult Plant Resistance to Septoria Tritici Blotch in Winter Wheat cv. Mandub (Triticum aestivum L.)

Agronomy ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1108
Author(s):  
Dominika Piaskowska ◽  
Urszula Piechota ◽  
Magdalena Radecka-Janusik ◽  
Paweł Czembor
Keyword(s):  
Mapping Population ◽  
Triticum Aestivum L ◽  
Seedling Stage ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Adult Plant ◽  
Resistance Locus ◽  
Phenotypic Variance ◽  
Breeding Programs ◽  
Plant Stage

Septoria tritici blotch (STB) is one of the most devastating foliar diseases of wheat worldwide. Host resistance is the most economical and safest method of controlling the disease, and information on resistance loci is crucial for effective breeding for resistance programs. In this study we used a mapping population consisting of 126 doubled-haploid lines developed from a cross between the resistant cultivar Mandub and the susceptible cultivar Begra. Three monopycnidiospore isolates of Z. tritici with diverse pathogenicity were used to test the mapping population and parents’ STB resistance at the seedling stage (under a controlled environment) and adult plant stage (polytunnel). For both types of environments, the percentage leaf area covered by necrosis (NEC) and pycnidia (PYC) was determined. A linkage map comprising 5899 DArTSNP and silicoDArT markers was used for the quantitative trait loci (QTL) analysis. The analysis showed five resistance loci on chromosomes 1B, 2B and 5B, four of which were derived from cv. Mandub. The location of QTL detected in our study on chromosomes 1B and 5B may suggest a possible identity or close linkage with Stb2/Stb11/StbWW and Stb1 loci, respectively. QStb.ihar-2B.4 and QStb.ihar-2B.5 detected on chromosome 2B do not co-localize with any known Stb genes. QStb.ihar-2B.4 seems to be a new resistance locus with a moderate effect (explaining 29.3% of NEC and 31.4% of PYC), conferring resistance at the seedling stage. The phenotypic variance explained by QTL detected in cv. Mandub ranged from 11.9% to 70.0%, thus proving that it is a good STB resistance source and can potentially be utilized in breeding programs.

scholarly journals Association Mapping and Transcriptome Analysis Reveal the Genetic Architecture of Maize Kernel Size

2021 ◽  
Vol 12 ◽  
Author(s):  
Juan Ma ◽  
Lifeng Wang ◽  
Yanyong Cao ◽  
Hao Wang ◽  
Huiyong Li
Keyword(s):  
Differential Expression ◽  
Genetic Architecture ◽  
Genome Wide Association Study ◽  
Differential Expression Analysis ◽  
Inbred Lines ◽  
Kernel Size ◽  
Maize Kernel ◽  
Association Panel ◽  
Kernel Length ◽  
A Genome

Kernel length, kernel width, and kernel thickness are important traits affecting grain yield and product quality. Here, the genetic architecture of the three kernel size traits was dissected in an association panel of 309 maize inbred lines using four statistical methods. Forty-two significant single nucleotide polymorphisms (SNPs; p < 1.72E-05) and 70 genes for the three traits were identified under five environments. One and eight SNPs were co-detected in two environments and by at least two methods, respectively, and they explained 5.87–9.59% of the phenotypic variation. Comparing the transcriptomes of two inbred lines with contrasting seed size, three and eight genes identified in the association panel showed significantly differential expression between the two genotypes at 15 and 39 days after pollination, respectively. Ten and 17 genes identified by a genome-wide association study were significantly differentially expressed between the two development stages in the two genotypes. Combining environment−/method-stable SNPs and differential expression analysis, ribosomal protein L7, jasmonate-regulated gene 21, serine/threonine-protein kinase RUNKEL, AP2-EREBP-transcription factor 16, and Zm00001d035222 (cell wall protein IFF6-like) were important candidate genes for maize kernel size and development.

scholarly journals Molecular Mapping of the Stb4 Gene for Resistance to Septoria tritici Blotch in Wheat

2004 ◽  
Vol 94 (11) ◽  
pp. 1198-1206 ◽  
Author(s):  
Tika B. Adhikari ◽  
Jessica R. Cavaletto ◽  
Jorge Dubcovsky ◽  
Jorge Omar Gieco ◽  
Ana Rosa Schlatter ◽  
...  
Keyword(s):  
Molecular Mapping ◽  
Bulked Segregant Analysis ◽  
Recombinant Inbred Lines ◽  
Single Gene ◽  
Effective Means ◽  
Wheat Chromosome ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Adult Plant ◽  
Field Season

Breeding wheat for resistance is the most effective means to control Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph Septoria tritici). At least eight genes that confer resistance to STB in wheat have been identified. Among them, the Stb4 locus from the wheat cv. Tadinia showed resistance to M. graminicola at both seedling and adult-plant stages. However, no attempt has been made to map the Stb4 locus in the wheat genome. A mapping population of 77 F10 recombinant-inbred lines (RILs) derived from a three-way cross between the resistant cv. Tadinia and the susceptible parent (Yecora Rojo × UC554) was evaluated for disease resistance and molecular mapping. The RILs were tested with Argentina isolate I 89 of M. graminicola for one greenhouse season in Brazil during 1999, with an isolate from Brazil (IPBr1) for one field season in Piracicaba (Brazil) during 2000, and with Indiana tester isolate IN95-Lafayette-1196-WW-1-4 in the greenhouse during 2000 and 2001. The ratio of resistant:susceptible RILs was 1:1 in all three tests, confirming the single-gene model for control of resistance to STB in Tadinia. However, the patterns of resistance and susceptibility were different between the Indiana isolate and those from South America. For example, the ratio of RILs resistant to both the Indiana and Argentina isolates, resistant to one but susceptible to the other, and susceptible to both isolates was approximately 1:1:1:1, indicating that Tadinia may contain at least two genes for resistance to STB. A similar pattern was observed between the Indiana and Brazil isolates. The gene identified with the Indiana tester isolate was assumed to be the same as Stb4, whereas that revealed by the South American isolates may be new. Bulked-segregant analysis was used to identify amplified fragment length polymorphism (AFLP) and microsatellite markers linked to the presumed Stb4 gene. The AFLP marker EcoRI-ACTG/MseI-CAAA5 and microsatellite Xgwm111 were closely linked to the Stb4 locus in coupling at distances of 2.1 and 0.7 centimorgans (cM), respectively. A flanking marker, AFLP EAGG/ M-CAT10, was 4 cM from Stb4. The Stb4 gene was in a potential supercluster of resistance genes near the centromere on the short arm of wheat chromosome 7D that also contained Stb5 plus five previously identified genes for resistance to Russian wheat aphid. The microsatellite marker Xgwm111 identified in this study may be useful for facilitating the transfer of Stb4 into improved cultivars of wheat.

scholarly journals A genome-wide association study unravels cytokinin as a major component in the root defense responses against Ralstonia solanacearum

2021 ◽  
Author(s):  
Alejandro Alonso-Díaz ◽  
Santosh B Satbhai ◽  
Roger de Pedro-Jové ◽  
Hannah M Berry ◽  
Christian Göschl ◽  
...  
Keyword(s):  
Association Study ◽  
Genome Wide Association Study ◽  
Allelic Variation ◽  
Defense Responses ◽  
Genome Wide Association ◽  
Root Growth Inhibition ◽  
Future Research ◽  
Cytokinin Signaling ◽  
Genome Wide ◽  
A Genome

Abstract Bacterial wilt caused by the soil-borne pathogen Ralstonia solancearum is economically devastating, with no effective methods to fight the disease. This pathogen invades plants through their roots and colonizes their xylem, clogging the vasculature and causing rapid wilting. Key to preventing colonization are the early defense responses triggered in the host’s root upon infection, which remain mostly unknown. Here, we have taken advantage of a high-throughput in vitro infection system to screen natural variability associated to the root growth inhibition phenotype caused by R. solanacearum in Arabidopsis during the first hours of infection. To analyze the genetic determinants of this trait, we have performed a Genome-Wide Association Study, identifying allelic variation at several loci related to cytokinin metabolism, including genes responsible for biosynthesis and degradation of cytokinin. Further, our data clearly demonstrate that cytokinin signaling is induced early during the infection process and cytokinin contributes to immunity against R. solanacearum. This study highlights a new role of cytokinin in root immunity, paving the way for future research that will help understanding the mechanisms underpinning root defenses.

scholarly journals Genomic insights into the origin, domestication and genetic basis of agronomic traits of castor bean

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Wei Xu ◽  
Di Wu ◽  
Tianquan Yang ◽  
Chao Sun ◽  
Zaiqing Wang ◽  
...  
Keyword(s):  
Castor Bean ◽  
Genetic Basis ◽  
Genome Wide Association Study ◽  
De Novo ◽  
Agronomic Traits ◽  
Ricinus Communis ◽  
Oilseed Crop ◽  
A Genome ◽  
Trait Locus ◽  
Wild Progenitors

Abstract Background Castor bean (Ricinus communis L.) is an important oil crop, which belongs to the Euphorbiaceae family. The seed oil of castor bean is currently the only commercial source of ricinoleic acid that can be used for producing about 2000 industrial products. However, it remains largely unknown regarding the origin, domestication, and the genetic basis of key traits of castor bean. Results Here we perform a de novo chromosome-level genome assembly of the wild progenitor of castor bean. By resequencing and analyzing 505 worldwide accessions, we reveal that the accessions from East Africa are the extant wild progenitors of castor bean, and the domestication occurs ~ 3200 years ago. We demonstrate that significant genetic differentiation between wild populations in Kenya and Ethiopia is associated with past climate fluctuation in the Turkana depression ~ 7000 years ago. This dramatic change in climate may have caused the genetic bottleneck in wild castor bean populations. By a genome-wide association study, combined with quantitative trait locus analysis, we identify important candidate genes associated with plant architecture and seed size. Conclusions This study provides novel insights of domestication and genome evolution of castor bean, which facilitates genomics-based breeding of this important oilseed crop and potentially other tree-like crops in future.

scholarly journals Genome-wide association study revealed loci linked to post-drought recovery and traits related to persistence of smooth bromegrass (Bromus inermis)

2021 ◽  
Author(s):  
Fatemeh Saeidnia ◽  
Mohammad Mahdi Majidi ◽  
Aghafakhr Mirlohi
Keyword(s):  
Water Stress ◽  
Association Analysis ◽  
Complex Traits ◽  
Genome Wide Association Study ◽  
Agronomic Traits ◽  
Genetic Dissection ◽  
Smooth Bromegrass ◽  
Population Structure Analysis ◽  
Stress Environments ◽  
Trait Associations

Association analysis has been proved as a powerful tool for genetic dissection of complex traits. This study was conducted to identify marker – trait associations for recovery, persistence, and as well as finding stable associations. In this study, a diverse panel of polycross derived progenies of smooth bromegrass was phenotyped under normal and water stress, during three consecutive years. Association analysis was performed between nine important agronomic traits along with three seasonal growth activity indices based on 535 SRAP markers. Population structure analysis identified five main subpopulations possessing significant genetic differences. Association analysis using mixed linear mode1 identified 339 and 233 marker-trait associations under normal and water stress environments, respectively. Some of these markers were associated with more than one trait; which can be attributed to pleiotropic effects or to a number of tightly linked genes affecting several traits. If the effectiveness of these markers in genetic control of these traits is validated, they could be potentially used for initiation of marker-assisted selection and targeted trait introgression of smooth bromegrass under normal and water stress environments.

Mapping for adult-plant resistance against Septoria tritici blotch in a common wheat line Murga

2020 ◽  
Author(s):  
Xinyao He ◽  
Gustavo Azzimonti ◽  
Mariel del Rosario Sánchez-Vidaña ◽  
Silvia Pereyra ◽  
Carolina Sansaloni ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Resistance Mechanism ◽  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Adult Plant ◽  
Wheat Line ◽  
Synthetic Wheat ◽  
Broad Spectrum Resistance ◽  
Fast Development ◽  
The One

Septoria tritici blotch (STB) is a major foliar disease globally, which is notorious in the fast development of fungicide resistance, making host resistance an indispensable component in mitigating STB. CIMMYT wheat line Murga is well known for its high, durable, and broad-spectrum resistance against STB infection, and the purpose of this study was to investigate its resistance mechanism to facilitate its utilization in breeding. A recombinant inbred line population was derived from a cross between Murga and a STB susceptible line Huirivis#1, comprising 297 progenies. The population was evaluated for adult-plant STB resistance in Toluca, Mexico (from 2017 to 2019), and in La Estanzuela, Uruguay (from 2016 to 2018). Genotyping was performed with the DArTSeq platform. QTL mapping indicated a major and stable QTL on chromosome 3DL, explaining a phenotypic variation for STB of 41.2-62.5% in Mexico and 27.5-40.3% in Uruguay. This QTL was regarded as Stb16 based on comparison of its physical position, the possible origin from synthetic wheat, and its broad-spectrum resistance. Additional QTL with minor effects were identified on chromosomes 2B, 2D, 3A, 3B, and 5B. The one on 5BS was significant in four out of the six environments and must be new. Murga was the resistant donor for all QTL, except for those on 2B and 3A. Being an elite breeding line, the Stb16 carrier Murga could be used as a promising STB resistance donor. The rational employment of Stb16 could contribute to STB management yet avoid the rapid emergence of Stb16-virulent isolates.

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