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Author: Nida Ghori
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Wheat is a staple food crop worldwide and insect damage is a major constraint for its production. Among the insects, Hessian fly (HF, Mayetiola destructor) is a destructive pest that significantly reduces wheat grain yield. To date, 37 HF resistant genes have been named, but diagnostic markers for these genes are lacking, which hampers their deployment in wheat breeding. HF resistance gene H34 on the short arm of chromosome 6B was one of the genes from a U.S. winter wheat Clark. To finely map H34, a cross was made between two F12 recombinant inbred lines (RIL115-S and RIL118-R) derived from Ning7840 x Clark. RIL118-R carries the resistance allele and RIL118-S carries the susceptibility allele at H34. Screening 286 (RIL115-S x RIL118-R) F3 lines using flanking Kompetitive Allele Specific PCR (KASP) markers identified five heterogenous inbred families (HIFs) segregating at H34. The first round of screening of 159 homozygous recombinant plants from five different HIFs using the KASP markers delimited H34 to a 5.0 Mb interval. Genotype-by-sequencing (GBS) analysis of the four pairs of near-isogenic lines (NILs) from the selected HIFs identified additional SNPs in the H34 region that further narrowed the H34 region to 1.3 Mb after screening 75 additional homozygous recombinant NILs. RNA-sequencing (RNA-seq) of the four pairs of NILs identified three differentially expressed genes (DEGs) in the H34 interval and they were considered as the putative H34 candidate genes for further study. Using the sequences of the DEGs and GBS-SNPs identified in the H34 interval, seven KASP markers were designed and validated to be diagnostic in a US winter wheat panel of 203 lines. These markers can be used in gene pyramiding of H34 with other HF resistance genes using marker-assisted selection (MAS) in the U.S. wheat-breeding programs. Furthermore, studying mechanism of HF resistance in wheat using RNA-seq data revealed that genes encoding defense proteins, stress-regulating transcription factors, and secondary metabolites were strongly up regulated within the first 48 hours of larval feeding, revealing an early defense in resistant wheat plants in response to larval attack. Also, HF feeding on resistant plants triggered the secretions of R-gene receptors by HF to initiate a hypersensitive response (HR) in the plants. This HR response resulted in production of reactive oxygen species (ROS) to up regulate the downstream genes involved in cell wall fortification and activation of different transcription factors (TFs), which prevents HF to access the nutrients in the resistant plants and eventually results in the death of HF larvae. The new knowledge generated in this study will aid in better understanding of HF-resistant mechanisms and developing new crop improvement strategies to increase HF resistance in wheat.
Author: Nida Ghori
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Wheat is a staple food crop worldwide and insect damage is a major constraint for its production. Among the insects, Hessian fly (HF, Mayetiola destructor) is a destructive pest that significantly reduces wheat grain yield. To date, 37 HF resistant genes have been named, but diagnostic markers for these genes are lacking, which hampers their deployment in wheat breeding. HF resistance gene H34 on the short arm of chromosome 6B was one of the genes from a U.S. winter wheat Clark. To finely map H34, a cross was made between two F12 recombinant inbred lines (RIL115-S and RIL118-R) derived from Ning7840 x Clark. RIL118-R carries the resistance allele and RIL118-S carries the susceptibility allele at H34. Screening 286 (RIL115-S x RIL118-R) F3 lines using flanking Kompetitive Allele Specific PCR (KASP) markers identified five heterogenous inbred families (HIFs) segregating at H34. The first round of screening of 159 homozygous recombinant plants from five different HIFs using the KASP markers delimited H34 to a 5.0 Mb interval. Genotype-by-sequencing (GBS) analysis of the four pairs of near-isogenic lines (NILs) from the selected HIFs identified additional SNPs in the H34 region that further narrowed the H34 region to 1.3 Mb after screening 75 additional homozygous recombinant NILs. RNA-sequencing (RNA-seq) of the four pairs of NILs identified three differentially expressed genes (DEGs) in the H34 interval and they were considered as the putative H34 candidate genes for further study. Using the sequences of the DEGs and GBS-SNPs identified in the H34 interval, seven KASP markers were designed and validated to be diagnostic in a US winter wheat panel of 203 lines. These markers can be used in gene pyramiding of H34 with other HF resistance genes using marker-assisted selection (MAS) in the U.S. wheat-breeding programs. Furthermore, studying mechanism of HF resistance in wheat using RNA-seq data revealed that genes encoding defense proteins, stress-regulating transcription factors, and secondary metabolites were strongly up regulated within the first 48 hours of larval feeding, revealing an early defense in resistant wheat plants in response to larval attack. Also, HF feeding on resistant plants triggered the secretions of R-gene receptors by HF to initiate a hypersensitive response (HR) in the plants. This HR response resulted in production of reactive oxygen species (ROS) to up regulate the downstream genes involved in cell wall fortification and activation of different transcription factors (TFs), which prevents HF to access the nutrients in the resistant plants and eventually results in the death of HF larvae. The new knowledge generated in this study will aid in better understanding of HF-resistant mechanisms and developing new crop improvement strategies to increase HF resistance in wheat.
Author: Anupama Joshi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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H13, a dominant resistance gene transferred from Aegilops tauschii into wheat (Triticum aestivum), confers a high level of antibiosis against a wide range of Hessian fly (HF, Mayetiola destructor) biotypes. Previously, H13 was mapped to the distal arm of chromosome 6DS, where it is flanked by markers Xcfd132 and Xgdm36. A mapping population of 1,368 F2 individuals derived from the cross: PI372129 (h13h13) / PI562619 (Molly, H13H13) was genotyped and H13 was flanked by Xcfd132 at 0.4cM and by Xgdm36 at 1.8cM. Screening of BAC-based physical maps of chromosome 6D of Chinese Spring wheat and Ae. tauschii coupled with high resolution genetic and Radiation Hybrid mapping identified nine candidate genes co-segregating with H13. Candidate gene validation was done on an EMS-mutagenized TILLING population of 2,296 M3 lines in Molly. Twenty seeds per line were screened for susceptibility to the H13-virulent HF GP biotype. Sequencing of candidate genes from twenty-eight independent susceptible mutants identified three nonsense, and 24 missense mutants for CNL-1 whereas only silent and intronic mutations were found in other candidate genes. 5' and 3' RACE was performed to identify gene structure and CDS of CNL-1 from Molly (H13H13) and Newton (h13h13). Increased transcript levels were observed for H13 gene during incompatible interactions at larval feeding stages of GP biotype. The predicted coding sequence of H13 gene is 3,192 bp consisting of two exons with 618 bp 5'UTR and 2,260 bp 3'UTR. It translates into a protein of 1063 amino acids with an N-terminal Coiled-Coil (CC), a central Nucleotide-Binding adapter shared by APAF-1, plant R and CED-4 (NB-ARC) and a C-terminal Leucine-Rich Repeat (LRR) domain. Conserved domain analysis revealed shared domains in Molly and Newton, except for differences in sequence, organization and number of LRR repeat in Newton. Also, the presence of a transposable element towards the C terminal of h13 was indicative of interallelic recombination, recent tandem duplications and gene conversions in the CNL rich region near H13 locus. Comparative analysis of candidate genes in the H13 region indicated that gene duplications in CNL encoding genes during divergence of wheat and barley led to clustering and diversity. This diversity among CNL genes may have a role in defining differences in the recognition specificities of NB-LRR encoding genes. Allele mining for the H13 gene in the core collection of Ae. tauschii and hexaploid wheat cultivars identified different functional haplotypes. Screening of these haplotypes using different HF biotypes would help in the identification of the new sources of resistance to control evolving biotypes of HF. Cloning of H13 will provide perfect markers to breeders for HF resistance breeding programs. It will also provide an opportunity to study R-Avr interactions in the hitherto unexplored field of insect-host interaction.
Author: Justin J. Wheeler
Publisher:
ISBN:
Category : Genetic markers
Languages : en
Pages : 120
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Author: Esra Alwan
Publisher:
ISBN:
Category :
Languages : en
Pages : 183
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Hessian fly and stripe rust are major pests of spring wheat in the Pacific Northwest and cultivar resistance is a primary breeding goal. Hessian fly (HF) infestations continue to cause significant yield losses in spring wheat in the Pacific Northwest. In wheat, resistance to Hessian fly is usually controlled in a gene for gene manner, similar to other pathosystems. Hessian fly resistance genes in wheat have been failing as a result to the rapid evolutionary pace of the insect. Stripe rust (denoted by Yr) is a destructive foliar disease of wheat casing damage on an annual basis. Most of the Yr named resistance genes have been overcome as a result of the continuing emergence of new virulence races. Genetic resistance remains the most effective and economical approach to minimize yield losses and respond to pathogen evolution. A doubled haploid (DH) mapping population was generated from a cross between two elite spring wheat lines; 'WA8076', and 'HT080158LU'. The DH population was genotyped with 90K SNP markers using the Illumina Infinium platform. Phenotypic assessment was carried out on the DH population for both Hessian fly and stripe rust response. The genotyping efforts resulted in a total 15,236 polymorphic SNP markers used to establish a high-density genetic map. A single Hessian fly resistance gene (HFR) derived from 'WA8076' was detected on the distal region of chromosome 6BS, flanked by two SNP markers IWB71431 and IWB61175 at a distance of 2.6 cM. In addition, a total of 13 genes/QTL were found to be associated with stripe rust resistance. The adapted superior lines with Yr resistance will be directly incorporated in subsequent breeding efforts as a durable source of resistance. The closely linked SNP markers to the resistance loci, identified in this study, will provide an effective tool to accurately identify, select, and integrate the HF and Yr resistance genes into existing wheat cultivars. The highly dense SNP-based genetic map provides useful information for fine mapping and finding candidate genes underlying QTLs as well as marker-assisted breeding. Furthermore, a genome-wide association study (GWAS) we performed for both seedling and adult plant response in a diverse population of winter wheat germplasm. The population was genotyped with the 90K iSelect wheat single nucleotide polymorphism (SNP) array. Our GWAS study identified a total of 26 loci, comprising a range of existing and novel loci associated with stripe rust resistance. Resistance loci in the winter wheat germplasm can be exploited in the development of broadly-effective disease-resistant commercial wheat cultivars.
Author: Tavin Marie Schneider
Publisher:
ISBN:
Category : Hessian fly
Languages : en
Pages :
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Wheat (Triticum aestivum L.) is one of the most important agricultural commodity crops in Washington. Each year, farmers face various production challenges, including Hessian fly [Mayetiola destructor (Say)], which can lead to devastating crop losses. Resistance genes are the most successful methods to manage and control this insect. Although there are at least 37 known Hessian fly resistance genes (HFR genes), few are deployed in the region, mostly due to a lack of molecular tools to support breeding efforts. Seahawk, a popular soft white spring wheat, contains resistance, but the gene identity is unknown. Using two recombinant inbred populations made from crossing soft white spring wheat cultivar Seahawk to spring club wheat cultivars JD and Melba, we set out to identify the source of resistance in Seahawk and to develop molecular markers that can be used to select for the gene in breeding populations. After acquiring the genetic marker information using Illumina’s 90K SNP technology, we were able to map the resistance gene to the distal end of the short arm of chromosome 6B and created three kompetitive allele specific PCR (KASP) markers that are effective in selecting for this gene in diverse backgrounds. Utilizing the Seahawk/JD population, we also studied how the wheat bread-making locus (wbm) affects the quality of soft white and club wheat. Soft white wheat and club wheat are produced and milled for their weak gluten properties and high starch contents that result in delicate crumb structures when baked. The wbm gene, however, is known to be associated with increased gluten strength properties and was identified in elite bread-making cultivars. At Washington State, the wbm gene is found at higher than expected frequencies among elite club and soft white wheat varieties. After testing the quality parameters of wbm isolines, we found that the locus does not negatively impact soft white wheat flour or dough properties.
Author: Zhengqiang Ma
Publisher:
ISBN:
Category :
Languages : en
Pages : 270
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Author: Muharrem Dilbirligi
Publisher:
ISBN:
Category : Wheat
Languages : en
Pages :
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Book Description
"Several pests causing about 25% yield loss/year attack wheat plant. Genetic control via manipulating resistance genes is the most effective and economical method of controlling pests using two conventional approaches, map-based cloning and transposon tagging. However, these methods were not effective to clone wheat resistance genes due to the fact that wheat has a larger genome, of which 95-99% is non-transcribing-nested cluster of retrotransposons and duplicated genes. Therefore, a gene cloning approach that target only the expressed portion of the genome and mapping approaches that physically localize genes into only gene containing regions are desirable for wheat. Irrespective of the host or the pest type, most resistance genes share a strong protein sequence similarity especially for domains and motifs. Also, expression profile of the majority of cloned resistance genes are unique. They are rarely and constitutively expressed. The objective of our study was to identify expressed resistance genes and physical localize them. Using modified RNA fingerprinting and data mining approaches, we identified 220 expressed resistance gene candidates out of the 728 analyzed. About 76% (167/220) were rare transcripts including 73 novel sequences. Irrespective of the cloning methods used, 184 out of 220 (36 unknown were eliminated) expressed resistance gene candidates were attempted to map physically. Physical mapping localized 310 resistance loci in wheat genome detected by the 121 candidate resistance gene sequences. Comparative analysis resulted in identification of 26 resistance gene cluster encompassing ̃16% of the wheat genome. Five major resistance gene clusters were observed to contain loci corresponding to 67 sequences. Wheat genome contains 269 morphologically characterized resistance genes. Two hundred twenty nine of them were genetically studied. Construction of consensus genetic maps using individual 137 genetic linkage maps allowed us to localize 110 (80 single gene inherited and 30 QTL type) morphologically characterized wheat resistance genes on the consensus genetic maps. Comparison of consensus genetic maps with consensus physical maps resulted in physical mapping of 80 single-gene-inherited and 10 QTL-type wheat resistance genes into 20 smaller chromosomal regions. About 93% (85 of 90) of the wheat resistance genes were localized into 18 smaller regions where 131 of the candidate resistance gene loci mapped. About 75% of both the morphologically characterized resistance genes and the identified candidate sequences mapped to the distal 20% of the chromosomal regions"--Abstract.
Author: Ramesh Arora
Publisher: Springer
ISBN: 9811060568
Category : Science
Languages : en
Pages : 433
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Book Description
This book reviews and synthesizes the recent advances in exploiting host plant resistance to insects, highlighting the role of molecular techniques in breeding insect resistant crops. It also provides an overview of the fascinating field of insect-plant relationships, which is fundamental to the study of host-plant resistance to insects. Further, it discusses the conventional and molecular techniques utilized/useful in breeding for resistance to insect-pests including back-cross breeding, modified population improvement methods for insect resistance, marker-assisted backcrossing to expedite the breeding process, identification and validation of new insect-resistance genes and their potential for utilization, genomics, metabolomics, transgenesis and RNAi. Lastly, it analyzes the successes, limitations and prospects for the development of insect-resistant cultivars of rice, maize, sorghum and millet, cotton, rapeseed, legumes and fruit crops, and highlights strategies for management of insect biotypes that limit the success and durability of insect-resistant cultivators in the field. Arthropod pests act as major constraints in the agro-ecosystem. It has been estimated that arthropod pests may be destroying around one-fifth of the global agricultural production/potential production every year. Further, the losses are considerably higher in the developing tropics of Asia and Africa, which are already battling severe food shortage. Integrated pest management (IPM) has emerged as the dominant paradigm for minimizing damage by the insects and non-insect pests over the last 50 years. Pest resistant cultivars represent one of the most environmentally benign, economically viable and ecologically sustainable options for utilization in IPM programs. Hundreds of insect-resistant cultivars of rice, wheat, maize, sorghum, cotton, sugarcane and other crops have been developed worldwide and are extensively grown for increasing and/or stabilizing crop productivity. The annual economic value of arthropod resistance genes developed in global agriculture has been estimated to be greater than US$ 2 billion Despite the impressive achievements and even greater potential in minimizing pest- related losses, only a handful of books have been published on the topic of host-plant resistance to insects. This book fills this wide gap in the literature on breeding insect- resistant crops. It is aimed at plant breeders, entomologists, plant biotechnologists and IPM experts, as well as those working on sustainable agriculture and food security.
Author: Peter A. Edde
Publisher: Academic Press
ISBN: 0128196998
Category : Technology & Engineering
Languages : en
Pages : 1004
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Book Description
Field Crop Arthropod Pests of Economic Importance presents detailed descriptions of the biology and ecology of important arthropod pest of selected global field crops. Standard management options for insect pest control on crops include biological, non-chemical, and chemical approaches. However, because agricultural crops face a wide range of insect pests throughout the year, it can prove difficult to find a simple solution to insect pest control in many, if not most, cropping systems. A whole-farm or integrated pest management approach combines cultural, natural, and chemical controls to maintain insect pest populations below levels that cause economic damage to the crop. This practice requires accurate species identification and thorough knowledge of the biology and ecology of the target organism. Integration and effective use of various control components is often enhanced when the target organism is correctly identified, and its biology and ecology are known. This book provides a key resource toward that identification and understanding. Students and professionals in agronomy, insect detection and survey, and economic entomology will find the book a valuable learning aid and resource tool. - Includes insect synonyms, common names, and geographic distribution - Provides information on natural enemies - Is thoroughly referenced for future research
Author: Timothy J. Gibb
Publisher: Academic Press
ISBN: 0124046924
Category : Science
Languages : en
Pages : 347
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Book Description
Contemporary Insect Diagnostics aids entomologists as they negotiate the expectations and potential dangers of the practice. It provides the reader with methods for networking with regulatory agencies, expert laboratories, first detectors, survey specialists, legal and health professionals, landscape managers, crop scouts, farmers and the lay public. This enables the practitioner and advanced student to understand and work within this network, critically important in a time when each submission takes on its own specific set of expectations and potential ramifications. Insect diagnosticians must be knowledgeable on pests that affect human health, stored foods, agriculture, structures, as well as human comfort and the enjoyment of life. The identification and protection of the environment and the non-target animals (especially beneficial insects) in that environment is also considered a part of insect diagnostics. Additionally, Integrated Pest Management recommendations must include any of a variety of management tactics if they are to be effective and sustainable. This greatly needed foundational information covers the current principles of applied insect diagnostics. It serves as a quick study for those who are called upon to provide diagnostics, as well as a helpful reference for those already in the trenches. - Includes useful case studies to teach specific points in insect diagnostics - Provides problem-solving guidance and recommendations for insect identification, threat potential, and management tactics, while accounting for the varying needs of the affected population or client - Contains numerous color photos that enhance both applicability and visual appeal, together with accompanying write-ups of the common pests
