Identification of Quantitative Trait Loci and Molecular Markers for Disease, Insent and Agronomic Traits in Spring Wheat (Triticum Aestivum L.) PDF Download
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Author: Arron Hyrum Carter
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 157
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Author: Arron Hyrum Carter
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 157
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Author: Izabela L. Ciechanowska
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 0
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Marker-assisted selection requires the identification of molecular markers associated with major genes and quantitative trait loci (QTL) using linkage analysis. In this study, we used 167 doubled haploid (DH) lines derived from two unregistered spring wheat (Triticum aestivum L.) parental lines that belong to the Canada Western Special Purpose (CWSP) class to map QTLs associated with five traits using inclusive composite interval mapping (ICIM). Using ICIM, least square means phenotype data across 3-4 environments, and a genetic map of 2,676 SNPs out of the wheat 90K SNP array, we identified ten QTLs associated with maturity (4A and 5B), plant lodging (4B, 5A, 5D, and 7D), grain yield (2D), leaf rust (4A) and stem rust (1A and 2B). Each QTL individually accounted for 6.0-22.3% of the phenotypic variance and together accounted for 8.6-38.2% of each trait. QTLs identified for rusts using ICIM had a minor effect (6.0-9.0%) or a major effect (22.3%). Our major effect QTL at 22.3% was discovered on chromosome 2B and contributed to stem rust response. Its physical location has been associated with disease response in previous studies. Results from this study provide additional valuable information to wheat researchers, in particular that the area on chromosome 2B should be considered for future analyses.
Author: Junli Zhang (Doctoral student)
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 416
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Grain yield (GY) is always the first priority in wheat (Triticum aestivum L.) breeding; however, progress in improvement of this trait is hampered due to quantitative inheritance, low heritability, and confounding environmental effects. Thanks to the advancements of high throughput genotyping and phenotyping technologies, both molecular markers and physiological traits are now promising indirect selection tools in breeding for this trait and other traits. Besides grain yield, grain quality is another important respect in wheat breeding, and one of the quality traits is the Hagberg falling number (FN), which is commonly used in grain grading. The FN test has a genetic component but is also strongly influenced by environmental conditions during the reproductive growth stage, including excessive moisture, extreme temperature, and biotic and abiotic stresses. The objective of the current studies was to identify potential genomic regions and molecular markers that influence GY, three important physiological traits (canopy temperature, CT; chlorophyll content index, CCI; flag leaf senescence, FLS) that could impact grain yield during heat and moisture stress, and FN by QTL mapping approaches. A winter wheat population of 159 recombinant inbred lines (RILs) from the cross of ID0444 and Rio Blanco were used to map QTL for GY, CT, CCI and FLS, and a total of 110 hard white spring (HWS) wheat accessions from the National Small Grain Collection (NSGC) were used in genome-wide association mapping of FN. GY was evaluated under three field conditions, rainfed, terminal drought (water stress applied after anthesis), and fully irrigated, with a total of six location-year environments. QTL mapping was conducted for main effect (G) of GY, and the genotype x environment interaction (GEI) effect of GY. A total of 17 QTL were associated with G and 13 QTL associated with GEI, and nine of 13 QTL for GEI were mapped in the flanking chromosomal regions of QTL for GEI. One QTL, Q.Gy.ui-1B.2 found on chromosome 1B, was associated with GY in all six individual environments. Significant QTL x environment interaction (QEI), QTL x QTL interaction (QQI) and QTL x QTL x environment (QQEI) were also identified. The present study showed that the QEI and QQI were as important as the QTL main effect of GY, and they should be taken into consideration in future QTL studies and marker-assisted selection (MAS). The three physiological traits, CT, CCI and FLS, which have been reported to be closely related to grain yield of wheat in diverse environments, were evaluated in two terminal drought and one rainfed environments in southeastern Idaho. Correlation results showed that CT and FLS were highly correlated with GY but the relationship between CCI and GY varied among the three environments. FLS was closely related to heading date (HD) and its effect on grain yield might be determined by HD in the RIL population used in the study. Stepwise multiple regression showed that CT and FLS could predict grain yield effectively and could be used as indirect selection criteria in wheat breeding. A total of 27 main effect QTL (M-QTL) were identified on 12 chromosomes, explaining 5 to 14% of phenotypic variation. Seven epistatic QTL (E-QTL) were identified for FLS and CCI and these could explain 9-25% of the phenotypic variation, but most of them did not have a main effect. Most of the QTL were reported for the first time. FN tests were conducted using grain flour samples from the 110 HWS wheat accessions grown in five environments. A total of 1,740 SNP markers were used to detect SNP-FN associations using both general linear model (GLM) and mixed linear model (MLM). A total of 13 QTL located in nine chromosomal regions were identified in both GLM and MLM approaches. These new QTL have the potential to increase the selection efficiency for wheat breeding, and can be further explored to identify candidate genes.
Author: Jose Fernandes Barbosa Neto
Publisher:
ISBN:
Category :
Languages : en
Pages : 214
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Author: Guomei Wang
Publisher:
ISBN:
Category : Soft wheat
Languages : en
Pages : 160
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Kernel hardness (KHA) is a major factor determining break flour yield (BFY) and end-use quality of common wheat (Triticum aestivum L.). Within the soft wheat class, genotypes with consistently softer grains than common soft wheat are considered to be 'extra-soft'. In addition, 'extra-soft' wheats have greater BFY than common soft wheat lines. In order to better understand this interrelationship, a set of 164 F6-recombinant inbred lines (RILs) developed from a soft x 'extra-soft' wheat cross was evaluated for KHA, BFY, and other related traits in six field environments. The estimates of broad-sense heritability for KHA and BFY ranged from 0.84 to 0.96 and 0.56 to 0.76, respectively. Significant environmental effects and genotype by environment interactions were detected for all traits evaluated. A comprehensive genetic linkage map was created with 650 molecular markers based on this mapping population. Three chromosome translocations, 1BL. 1RS, 2N^S-2AS. 2AL and 5B:7B, were identified during linkage analysis. A total of 47 quantitative trait loci (QTL) were identified for nine traits including KHA, BFY, bran yield (BRN), unground middling yield (MID), plant height (PHT), days to heading (HDD), thousand-kernel weight (TKW), grain protein content (GPC), and test weight (TWT). The number of QTL per trait ranged from three for MID to nine for GPC. The phenotypic variance explained by individual QTL ranged from 5.8 to 47.6%. Among five QTL identified for KHA, the two most important QTL were located on chromosomes 4DS (Xbarc1118-Rht-D1 interval) and 4BS (Xwmc617-Rht-B1 interval), indicating that the 'extra-soft' characteristic was not controlled by the 5DS Hardness (Ha) locus which encodes the two puroindoline genes pinA and pinB. The co-location of QTL for KHA, BFY, BRN, and MID on 4DS suggested that genetic factors affecting KHA may have a pleiotropic effect on BFY. Two co-located QTL for TWT, TKW and PHT were detected on 4DS and 4BS, and a QTL for HDD was detected on 4DS, indicating that these QTL may represent the consequence of the semi-dwarfing green-revolution genes Rht-D1 and Rht-B1 located on 4DS and 4BS, respectively. Additional analysis suggested that the QTL for KHA on 4DS and 4BS are the effects of genes linked to Rht-D1 and Rht-B1, rather than pleiotropic effects of these genes. Some coincident QTL for the traits that were evaluated represent the interrelationships of phenotypic traits, where both KHA and BFY were associated with HDD and TWT based on path coefficient analysis. Association mapping can be an effective means for identifying, validating, and fine mapping genes and QTL in crop plants. To test this approach, a set of 94 diverse elite wheat lines was phenotyped for five important traits and genotyped with 487 molecular markers. In this study, the marker-trait association analysis showed that the gene pinB (Ha locus) was significantly associated with KHA as it is known to define the difference between soft and hard wheat classes. Additionally, the significant associations of marker XwPt-7187 with KHA, XwPt-1250 and XwPt-4628 with TWT, and Xgwm512 with PHT mark the first report of such associations in these genomic regions. This study, aiming at the genetic dissection of wheat kernel extra-softness and related traits, enhanced our understanding of both genetic control of and environmental effects on these important traits. Path coefficient analysis showed the promise of an alternative phenotypic selection approach that is more cost effective than direct measurement of kernel quality. Three chromosome translocations were discovered and their approximate chromosome break points were located. Numerous QTL were identified for these important traits. The major QTL can serve as a start point for fine mapping that eventually lead to the cloning of the QTL through map-based or candidate gene approach. Association mapping, as an alternate approach and complementary tool to QTL mapping, was demonstrated feasible in wheat for identification of marker-trait associations and cross validation of QTL or genes identified from bi-parent mapping populations.
Author: Jay Robert Kalous
Publisher:
ISBN:
Category : Durum wheat
Languages : en
Pages : 116
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Desirable agronomic traits are similar for common hexaploid (6X) bread wheat (Triticum aestivum, 2n = 6x = 42, genome, AABBDD) and tetraploid (4X) durum wheat (T. turgidum durum, 2n = 4x = 28, genome, AABB). However, bread and durum wheat are genetically isolated from each other due to an unequal number of genomes that cause sterility when crossed. Previous work allowed identification of a 6X and 4X parent that when crossed resulted in a large number of recombinant progeny at both ploidy levels. In this study, interspecific recombinant inbred line populations at both 4X and 6X ploidy with 88 and 117 individuals, respectively, were developed from a cross between Choteau spring wheat (6X) and Mountrail durum wheat (4X). Lines within each population contained a mixture of alleles from each parent for loci in the A and B genomes. The presence of the D genome in the 6X population resulted in increased yield, tiller number, and seed size. The D genome also resulted in a decrease in stem solidness, lower test weight and fewer seed per spike. Similar results were found with a second RIL population containing 152 lines from 18 additional 6X by 4X crosses. Several additional QTL for agronomic and quality traits were identified in both the 4X and 6X populations. Positive durum alleles increasing kernel weight in hexaploids, on chromosomes 3B and 7A may be useful for introgression by bread wheat breeders.
Author: Khalil Zaynali Nezhad
Publisher:
ISBN:
Category :
Languages : en
Pages : 267
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Two bread wheat (T. aestivum L.) accessions were selected as parental lines. Population genotyping was conducted on 143 F2 plants and phenotyping was carried out on 133 F2:3 families. The molecular genetic linkage map was constructed including 293 loci associated to 19 wheat chromosomes. There are 76 new loci compared to the ITMI map. The analysis revealed eight QTLs for days to flowering and seven QTLs for plant height. Five QTLs for spike length were identified. The QTL for seed length on chromosome 5B was mapped for all trait measurements under both conditions. The present study revealed four and six QTLs for thousand-grain weight under control and stress conditions, respectively. Only one QTL on chromosome 4BL was common for both conditions. Five QTLs for thousand-grain weight were found to be specific to stress condition on chromosomes 1B, 4AL, 7AS, and 7DS. Identifying QTLs for thousand-grain weight under post-anthesis drought stress on chromosomes 7DS, 7AS, and 4AL and considering the known reciprocal translocation of 4AL/7BS in wheat, revealed the importance of the chromosomes from the homoeologous group 7 of Triticeae.
Author: Yvonne Alexandria Thompson
Publisher:
ISBN:
Category :
Languages : en
Pages : 130
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Wheat (Triticum aestivum L.) is one of the world's staple crops essential to global food security; however, its profitable production can be threatened by soil-borne diseases. The fungus, Fusarium culmorum, and cereal cyst nematode, Heterodera filipjevi, are two types of soil-borne pathogen/pest that drastically reduce yield in wheat production areas worldwide. However, few sources of plant resistance have been identified for either, making knowledge of genetic regions associated with resistance imperative. An integrated approach, requiring the use of host plant resistance, is necessary for management of these diseases. Our aim is to contribute to this integrated approach by identifying sources of resistance for applied use. We sought to identify quantitative trait loci (QTL) related to genetic resistance against F. culmorum in diverse germplasm. A population of 600 wheat accessions was phenotyped for disease using an enhanced screening system to better separate susceptible and resistant responses. The accessions screened showed differential responses among genotypes of wheat, reflecting genetic variability under disease pressure. Genotypic data was acquired using the Illumina wheat 9K iSelect SNP chip. A Genome-wide Association Study (GWAS) was conducted using the R software and FARM CPU package to evaluate marker-trait associations. Marker-trait associations at or above the Bonferroni threshold of 0.05 were identified on chromosomes 1A, 5A, and 6B. Chromosomes 5A and 6B may likely reflect novel sources of resistance. We also aimed to identify quantitative trait loci (QTL) related to genetic resistance against H. filipjevi in spring wheat breeding lines and cultivars adapted to the Pacific Northwest. Naturally infested soils, containing predominately H. filipjevi, were used to screen 138 wheat varieties, revealing variability in response to nematode infection. The selected germplasm was genotyped using a genotype-by-sequencing approach and marker-trait associations were evaluated using the R software and FARM CPU package. Marker-trait associations at or above the Bonferroni threshold of 0.05 were identified on chromosomes 2B, 5B, and 7B. The identified QTL for resistance should be validated and further explored for their usefulness in marker assisted breeding.
Author: Hua Chen
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 168
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Early maturity, grain yield and grain protein content are some of the important traits in western Canadian wheat breeding programs. A series of experiments were conducted to explore the genetic basis of days to heading, and maturity, plant height, grain protein, grain yield and related traits. In a spring wheat population of 187 recombinant inbred lines genotyped with 341 Diversity Array Technology (DArT) polymorphic markers, a total of 21 quantitative trait loci (QTLs) were identified for all phenotypic traits recorded, except plant height and grain protein content. Two earliness per se QTLs were mapped on chromosomes 1A (QEps.dms-1A) and 4A (QEps.dms-4A) in all three growing seasons, contributing 15-27% and 8-10%, respectively, to the total genetic variation in days to maturity. The two earliness QTLs and Vrn-B1 exhibited additive interaction. In the same population, lines carrying the resistant allele of Lr34/Yr18 were taller, matured earlier, yielded less grain with lower test weights than lines without Lr34/Yr18. Lines with Lr34/Yr18 also exhibited lower leaf and stripe rust infection than lines with the susceptible allele. The failure to combine Lr34/Yr18 with high yield, protein, and SDS sedimentation suggested single seed descent or doubled haploid populations for the combined selection of multiple quantitatively inherited traits, and simply one molecular marker, would require population sizes in excess of at least 500 to have any possibility of selection success. Genetic diversity analysis for earliness related and plant height reducing genes in 82 spring wheat cultivars registered in western Canada through eight diagnostic DNA markers suggested breeding efforts in western Canada have resulted in the incorporation of vernalization and photoperiod insensitive and height reducing genes in modern cultivars to promote early maturity, to make use of off-season nurseries in other parts of the world and to improve lodging tolerance. Using genome-wide association mapping (GWAS). we identified a total of 152 significant marker-trait associations; however, there were only 18 genomic regions that consisted of clusters of 3 to 20 significant single nucleotide polymorphisms (SNPs) across 12 chromosomes, including two regions each for grain yield, test weight and protein content, six regions for plant height and six other coincident regions that were associated with two or three traits. The genomic region associated with plant height on chromosome 4B showed high linkage disequilibrium (r2 > 0.80) with the semi-dwarfing gene Rht-B1. Results of these studies suggest that besides the widely used semi-dwarf and early maturity related genes, there is a wide spectrum of loci available that could be used for modulating plant height, days to maturity, grain yield and grain protein content in western Canadian wheat germplasm.
Author: Stella Salvo
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages : 190
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