Download or read book Partial Resistance to Phytophthora Root Rot in Soybean and Association with Tolerance to Saturated Soil Conditions written by William Jay Werk and published by . This book was released on 2005 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Genome wide Analyses for Partial Resistance to Phytophthora Sojae Kaufmann and Gerdemann in Soybean glycine Max L Merr Populations from North America and the Republic of Korea written by Rhiannon N. Schneider and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Phytophthora root and stem rot of soybean (Glycine max) is caused by the oomycete pathogen Phytophthora sojae. This disease can be controlled by genetic resistance, but can cause devastating yield losses in fields planted with susceptible soybean cultivars and results in losses of around $300 million annually in the US. Partial resistance is considered to be more durable against P. sojae than race-specific resistance conferred by Rps genes and is theoretically effective against all races of this pathogen. Evaluation of a historical set of public cultivars representing 80 years of soybean breeding indicated that there have been genetic gains for partial resistance; however, these gains may have begun to plateau in the 1970s to early 1980s. Cultivars developed in Ohio generally have high levels of partial resistance to P. sojae; however, there is little known about the genetic regions associated with the partial resistance. Further improvement of increasing partial resistance could be achieved through the introgression of known quantitative trait loci (QTL) from plant introductions from the Republic of Korea (South Korea), which contain high levels of partial resistance. From an analysis of 1,398 plant introductions with a wide range of phenotypic expression of resistance, sixteen single nucleotide polymorphisms (SNPs) were associated with partial resistance to P. sojae. These SNPs were located in three genomic regions, or QTL, on chromosomes 3, 13, and 19. The QTL on chromosome 19 represented a novel locus, whereas the QTL on chromosomes 3 and 13 were coincident with previously identified QTL for partial resistance and/or Rps genes. In contrast, a genome-wide association study carried out in Ohio breeding lines was unable to detect any significant marker-trait associations, limiting the ability to use marker assisted selection to improve partial resistance in this population. However, genomic selection (GS) was shown to be a promising means of selection, with efficiencies relative to phenotypic selection of 0.5 to 1. Importantly, GS can be implemented through use of multi-trait indices which include yield. As exotic germplasm with high levels of partial resistance are identified, GS may be a valuable tool for utilizing exotic sources of partial resistance to P. sojae while maintaining or improving yield.

Download or read book Characterization of a Major Quantitative Disease Resistance Locus for Partial Resistance to Phytophthora Sojae written by Stephanie Renae Karhoff and published by . This book was released on 2019 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phytophthora root and stem rot is caused by the soil-borne oomycete Phytophthora sojae. Host resistance is the main management practice for Phytophthora root and stem rot, and breeders have historically relied on single, major resistance (Rps) genes. However, pathogen populations have adapted to the previously deployed Rps genes. An alternative is to breed for higher levels of partial resistance, which is quantitatively inherited and typically non isolate-specific. Partial resistance is controlled by multiple quantitative disease resistance loci (QDRL). A QDRL explaining up to 45% of the phenotypic variation (PV) was previously identified in plant introduction (PI) 427106 and PI 427105B (QDRL-18). Major QDRL are rare in the soybean – P. sojae pathosystem; thus, near isogenic lines (NILs) contrasting at QDRL-18 were developed and used to test for isolate-specificity, pleiotropic effects, and validate the locus across environments and genetics backgrounds. Resistant introgressions from either PI 427105B or PI 427106 were effective against seven P. sojae isolates of varying pathotype complexity and increased resistance to P. sojae by 11-20% and 35-40% in laboratory and greenhouse assays, respectively. Furthermore, within the NIL set 4060, lines carrying resistant introgression R105B significantly out-yielded lines with the susceptible introgression SOX under highly favorable disease conditions. In order to facilitate future gene cloning and marker-assisted-selection, RNA-Sequencing of a subset of NILs was completed in conjunction with high resolution mapping of this locus. High-resolution mapping of QDRL-18 with 224-233 markers reduced the original 1,852 Kb interval to a 731 Kb region. Within the refined QDRL, seven genes were differentially expressed following inoculation with P. sojae. Of these seven, one gene putatively encoding a receptor-like protein kinase was significantly downregulated in NILs carrying the resistant introgression derived from PI 427105B at all tested time points. The narrowed QDRL-18 region will provide more closely linked markers and prioritizes candidate genes for future functional analyses. Finally, an obstacle to better understanding the genetic mechanisms of quantitative disease resistance is the identification of causal genes underlying resistance loci. Expression quantitative trait loci (eQTL) analysis has emerged as a method for candidate gene identification, but it requires that the population and conditions in which transcript abundance levels and phenotypic values are obtained be the same. Thus, phenotypic quantitative trait loci (pQTL) were identified in a separate mapping population, derived from a cross between `Conrad’ and `Sloan’, to leverage a larger eQTL study aimed at identifying resistance mechanisms. Two suggestive and one significant pQTL were identified on chromosomes 10 and 18. Most notably, a cis-eQTL coincided with pQTL located on chromosome 18 and is associated with the expression of a gene putatively encoding a leucine-rich repeat receptor-like protein kinase. Overall, this work contributes to the ongoing effort to (1) better understand the mechanisms associated with partial resistance to P. sojae and (2) develop soybean cultivars with increased levels of partial resistance.

Download or read book Identification of Quantitative Trait Loci for Partial Resistance to Phytophthora Sojae in Six Soybean glycine Max L Merr Plant Introductions written by Sungwoo Lee and published by . This book was released on 2013 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In soybean [Glycine max (L.) Merr.], Phytophthora root and stem rot caused by Phytophthora sojae is one of the destructive diseases that result in economic losses around the world. However, changes in P. sojae populations emphasize the integrated use of Rps gene-mediated resistance with partial resistance for more durable and effective defense. Quantitative trait loci (QTL) for partial resistance to P. sojae have been identified in several studies albeit in only a few genetic sources, primarily the cultivar Conrad. The first objective was to characterize six soybean plant introductions originating from East Asia for QTL conditioning partial resistance to P. sojae. The second objective was to evaluate joint-population QTL analysis (via joint inclusive composite interval mapping, JICIM) for the effectiveness of combining multiple populations with heterogeneous experimental conditions. Four populations were F7:8 and two were F4:6 generations, and they were mapped with partially overlapping sets of molecular markers. Resistance was measured either by lesion length in tray tests, or by root colonization, plant weight, root fresh weight, and root dry weight in layer tests. Conventional bi-parental QTL analysis identified ~12 QTL for a measurement in each population via composite interval mapping (CIM) using MapQTL5, which explained ~58% of total phenotypic variance (PV) in each population. Individually, most QTL explained less than 10% of PV. Interestingly, most of the QTL identified in this study mapped closely to other resistance QTL associated with resistance to other pests or pathogens or R-gene clusters. Joint-population QTL analysis (JICIM) detected the same QTL which were identified in each single-population analysis (Inclusive composite interval mapping, ICIM). In one pair of two populations with the fewest confounding factors, joint-population analysis detected an additional QTL; however this was not identified when all six of the populations were combined. In another population which had 128 RILs, no QTL were identified using the ICIM method compared to 1 QTL identified with MapQTL5. When populations were combined that were evaluated with different phenotypic methods, the same QTL were identified in the combined analysis compared to each population analyzed independently. Thus differences in phenotypic analysis did not largely affect the detection of these QTL. This study identified some limits in the use of joint linkage analysis and parameters for combining populations to detect additional QTL. Detection of additional QTL with this analysis will be enhanced if the populations are advanced beyond the F4, markers are fully integrated into large chromosome segments, and populations are sufficiently large. More importantly, populations which were evaluated with different phenotypic methods can be combined, provided common checks were used and data were normalized with the checks’ values. Many of the QTL identified in these six populations through both analyses overlapped at multiple genomic positions, while many were distinct from QTL identified in Conrad. This suggests that the QTL identified in this study will be useful in diversifying the US soybean cultivars and providing new genes to enhance resistance to P. sojae through breeding.

Download or read book The Relationship Between Tolerance to Phytophthora Root Rot and Yield of Soybean written by Daniel R. Scott and published by . This book was released on 1992 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Incomplete Resistance to Phytophthora Sojae in Soybean written by Santiago Xavier Mideros Mora and published by . This book was released on 2006 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Phytophthora root and stem rot caused by Phytophthora sojae, is a serious limitation to soybean production in the United States. Extensive deployment of Rps genes in soybean cultivars has led to adaptations in the P. sojae populations. Partial resistance to P. sojae in soybeans is effective against all races of the pathogen and is a form of incomplete resistance where the plant reduces the rate of colonization of the pathogen. In addition to partial resistance other types of incomplete resistance have also been described. Rps2 is a single dominant gene that confers incomplete resistance in soybean hypocotyls. Root resistance, thought to be quantitatively inherited, is another form of race specific resistance that appears to function only in the roots. In order to differentiate partial resistance from the other types of incomplete resistance that are race specific, components of resistance were analyzed and the cytology of infection compared. For this study attempts to genetically transform P. sojae to express a marker gene were unsuccessful. Three components were measured (lesion length, oospore production and infection frequency) in 8 soybean genotypes that were inoculated with non-transformed P. sojae isolates on the roots. Light and epifluorescent microscopy were used to study transversal cuts of Trypan blue stained root samples that were also inoculated with P. sojae. Soybean partial resistance was found to be composed of various components that interact to produce the partial resistance phenotype for defense against P. sojae in the roots. It was also found that the Rps2 and root resistant genotypes had significantly reduced levels for all of the components of resistance studied in comparison to the partially resistant genotype Conrad. However, the high levels of partial resistance in Jack were indistinguishable from the Rps2 reaction for all the components studied. In the cytology study it was found that P. sojae penetrates into all the soybean incomplete resistant genotypes: partial resistant, Rps2, and root resistant. Several mechanisms of resistance were observed: i) the resistance phenotype (Rpsla) contained the pathogen biotrophic growth from between 0 to 24 hal in a hypersensitive response; ii) Rps2 and root resistance phenotypes, also stopped growth of the pathogen but this occurred between 24 and 48 hal in a delayed hypersensitive response and iii) the partial resistance and the susceptible phenotypes allowed biotrophic colonization ofF. sojae. Finally a methodology to differentiate among mechanisms of incomplete resistance to P. sojae in soybean was identified based on the number of dead cells and extent of colonization that differed in partial resistance and Rps2 phenotypes.

Download or read book Evaluation of Soybean Cultivars for Partial Resistance and Tolerance to Phytophthora Sojae written by Catalina Ferro and published by . This book was released on 2005 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Identification and Dissection of Soybean QTL Conferring Resistance to Phytophthora Sojae written by Hehe Wang and published by . This book was released on 2011 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Phytophthora root and stem rot is the second most serious soybean disease in the USA. Partial resistance in soybean confers a broad-spectrum resistance to Phytophthora sojae and is expressed as reduced infection efficiency, smaller root lesions and reduction in oospore production, and is conferred by quantitative trait loci (QTL). In several host-pathosystems, the detection of an individual QTL differed depending on the specific pathogen isolate or phenotypic assay that was used. In soybean-P. sojae interaction, few broad-spectrum QTL have been identified and very little is known about the molecular mechanisms that contribute to this trait. The hypotheses for this study were that: i) there were more QTL in soybean conferring resistance to P. sojae; ii) soybean QTL with minor effect would respond differentially to P. sojae isolates and phenotypic assays; iii) candidate genes underlying the QTL vary in sequence between the resistant and susceptible genotypes, as well as different expression response during P. sojae infection; and iv) a complex network of defense-pathways is underlying each soybean QTL conferring resistance to P. sojae. Thus the first objective of this study was to map soybean QTL conferring broad-spectrum resistance to P. sojae in the soybean cultivar 'Conrad'. A F 4:6 population from a cross of Conrad and susceptible 'Sloan' was challenged with three P. sojae isolates using two different phenotypic assays. Ten QTL were identified on Chr. 8, 12, 13 (13-1, 13-2), 14, 17, 18 (18-1, 18-2), and 19 (19-1, 19-2). Of these, the QTL 18-2, 19-1, and 19-2 from Conrad, responded to multiple isolates as well as both phenotypic assays, and explained the largest percent of phenotypic variation. RILs with resistance alleles at these QTL had significantly higher yields than those with susceptible alleles in a P. sojae infested field. These QTL were further confirmed in the Conrad x Sloan F 6:8 population. These results indicate these three QTL as the best candidates for resistance breeding. The second objective of this study was to identify the candidate genes conferring partial resistance under these QTL. Microarray analysis identified genes with significantly different expression patterns between Conrad and Sloan, both constitutively and following inoculation. Of these genes, those co-localized with the QTL encoded proteins with unknown functions, or proteins related to defense or physiological traits. Seventeen genes were selected and their expression patterns were confirmed by qRT-PCR. The QTL 19-1 and 19-2 were further dissected by sequence and expression analysis of genes between the resistant and susceptible genotypes. A total of 1025 SNPs were identified between Conrad and Sloan through sequencing of 153 genes. A list of candidate genes with significantly different infection response between the resistant and susceptible lines were identified, including those involved in signal transduction, hormone-mediated pathways, plant cell structural modification, ubiquitination, and basal resistance. These findings suggest a complex defense network with multiple mechanisms underlying individual soybean QTL conferring resistance to P. sojae. Overall, this study will contribute to soybean resistance breeding by providing additional QTL, candidate genes and SNP markers for marker-assisted resistance breeding.

Download or read book Studies in the Management of Pythium Seed and Root Rot of Soybean written by Kelsey L. Scott and published by . This book was released on 2018 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Ohio, soybean seedling damping-off and seed rot are problems routinely encountered soon after planting. Reduced tillage systems that lead to inoculum build-up combined with saturated soil conditions are ideal environments for seedling diseases, which cause large losses of soybean stand and thus yield. Prior Ohio field surveys identified multiple species of Pythium and Phytophthora that contribute to soybean seedling damping-off. Among the most common and aggressive species are Phytophthora sojae, Pythium irregulare, Pythium ultimum var. ultimum, and Pythium ultimum var. sporangiiferum. Fungicide seed treatment and host resistance are two management strategies that are used to minimize yield loss caused by these pathogens. Thus, the objectives of these studies were to: i) evaluate new active ingredients for efficacy in the lab and field, and ii) identify and characterize new sources of resistance towards the most common seedling pathogens. These are key strategies for the development of effective strategies for the management of soybean seedling disease. During 2014-2015, at two environments, ethaboxam seed treatments combined with metalaxyl on a susceptible cultivar significantly increased yield compared to other fungicide treatments containing metalaxyl or mefenoxam alone. Soybeans treated with ethaboxam plus metalaxyl had significantly higher plant populations when compared to the nontreated control at all four 2016 field locations, while one environment had significantly higher yield. In laboratory seed plate and greenhouse cup assays, ethaboxam plus metalaxyl in a commercial formulation provided equal or better protection against multiple species of Pythium when compared with other seed treatments that contained metalaxyl or mefenoxam only. These results indicate that ethaboxam with metalaxyl is effective at managing seed and rot root caused by the diverse species of Pythium and Phytophthora and provides another seed treatment fungicide available to producers which can be used in an integrated disease management program. The parents that were used to develop six nested association mapping (NAM) populations were previously identified as segregating for resistance towards Phytophthora sojae, Pythium irregulare, Pythium ultimum var. ultimum, and Pythium ultimum var. sporangiiferum. Following inoculation in a cup assay, the resistance was quantitatively inherited in each of the NAM populations towards the four seedling pathogens. In total, 33 QDRL from the six populations surpassed the genome-wide logarithm of odds (LOD) threshold and there was a large number of suggestive QDRL that surpassed the chromosomal LOD threshold. Of these 33 significant QDRL, 10 explained more than 15% of the phenotypic variation. Only four QDRL conferred resistance to more than one of the oomycete pathogens; one on chromosome 3, one on chromosome 17, and two located at separate locations on chromosome 13. This indicates that there may be multiple mechanisms for resistance to these root pathogens. Further analyses are needed to precisely map these QDRL so they may be selectively bred into highly resistant germplasm in order to manage seed and seedling damping-off. These NAM populations will serve as a rich resource for breeders to incorporate resistance into adapted soybean cultivars.

Download or read book Races of the Pathogen Phytophthora Sojae Found in Michigan and Factors Affecting Root Rot of Soybean written by Richard Chemjor Kaitany and published by . This book was released on 2000 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanisms of Resistance and Candidate Gene Analysis Towards Fusarium Graminearum and Phytophthora Sojae in Soybean written by Cassidy Renee Gedling and published by . This book was released on 2018 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerous diseases affect soybean [Glycine max (L.) Merr] yields throughout the growing season in Ohio. Two soil borne pathogens Fusarium graminearum and Phytophthora sojae are known to reduce stand and yield. Currently, fungicide seed treatments are used to manage these pathogens, however, host plant resistance is often the best management strategy for field crops. Thus, the overall objective of the five chapters this dissertation was to identify mechanisms and candidate genes of resistance that are effective towards seed, seedling, and root rots caused by Fusarium graminearum and P. sojae in soybean. Quantitative disease resistance loci (QDRL) have been mapped in two separate recombinant inbred line (RIL) populations for resistance to Fusarium graminearum . In the F7:8 RIL derived from a cross Magellan X PI 567516C, one major QDRL was mapped. Fine mapping of this region identified four putative candidate genes for resistance to Fusarium graminearum . In an additional population of Wyandot x PI 567301B, a major and minor QDRL was mapped to chromosome 8 and 6, respectively. Hybrid genome assembly, fine mapping, and RNA sequencing analysis narrowed the major QDRL to 2.5 cM containing three putative candidate genes for resistance or susceptibility. To validate these candidate genes functional analysis needs to be assessed at the seed level. To achieve this we modified the Apple latent spherical virus (ASLV) which allowed for direct inoculation of VIGS-triggering ALSV agro-infiltrated Nicotiana benthamiana leaves onto soybean unifoliates. However, this method is genotype dependent; the virus is detected in numerous reproductive structures including pods, embryos, stems, leaves, and roots. The last objective of this dissertation focuses on mechanisms of partial resistance to Phytophthora sojae . This oomycete is a leading pathogen of soybean, causing root and stem rot (PRR) across the North Central Region in the U.S. Twenty phenotypic quantitative trait loci (pQTL) were previously mapped in a F9:11 Conrad x Sloan recombinant inbred line (RIL) population on chromosomes 1, 4, 9, 15, 16, 18, and 19; however, these regions encompass large portions of the genome. Thus a systems genetics approach that incorporates expression QTL (eQTL) mapping, functional genomics, and gene co-expression analysis was taken to identify molecular mechanisms contributing towards partial resistance, with the specific objective of reducing the list of candidate genes potentially underpinning pQTL. A greater number of eQTL were mapped in inoculated samples relative to mock, indicating transcriptional reprogramming due to P. sojae infection. Of the six co-expression modules identified, three were related to PRR susceptibility driven by three casual hotspots. GO enrichment of casual hotspot GM_17_D indicates that cell wall modification is a putative mechanism for P. sojae resistance. A total of four eQTL and one eQTL hotspots were found to be co-localized with pQTL and identified five candidate genes for resistance.

Download or read book Evaluation of Soil Compaction Plant Density and Resistance to Phytophthora Root Rot in Soybeans written by Craig Keith Moots and published by . This book was released on 1985 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book QTL Mapping of Phytophthora Root Rot Resistance and Aphid Resistance in Soybean written by Zhongnan Zhang and published by . This book was released on 2012 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Linkage Relations Between Resistance to Phytophthora Root Rot and Plant and Seed Characteristics in the Soybean written by Md. Fazlul Haque and published by . This book was released on 1962 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heritability of Tolerance to Phytophthora Root Rot in Two Three and Four parent Soybean Populations written by Karl D. Glover and published by . This book was released on 1996 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Master s Theses Directories written by and published by . This book was released on 2006 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".

Download or read book Integrated Management of Phytophthora Stem and Root Rot of Soybean and the Effect of Soil applied Herbicides on Seedling Disease Incidence written by Vinicius Castelli Garnica and published by . This book was released on 2019 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soybean seedling diseases and Phytophthora stem and root rot (PSRR; caused by Phytophthora sojae) are two of the most economically important diseases in North Central U.S. Remarkable differences in disease incidence occur each year, which demonstrate that abiotic and biotic factors must interact for disease onset and development. During 2017 and 2018, field studies were conducted to (i) address the efficacy of seed treatment and genetic resistance for PSRR management on soybean population, canopy coverage (CC), and yield, and (ii) investigate potential interactions between pre-emergence (PRE) herbicides and the incidence of seedling diseases in alluvial soils in Nebraska. Despite field history, PSRR developed in only four of six environments studied. Commercial seed treatment had a positive effect on plant population density, CC, and yield in at least three environments. Compared to non-treated control, seed treatment increased emergence between 11,600 to 53,700 plants ha-1 and early-season CC between 0.7 to 1.2%. Under high disease pressure, management programs using moderately resistant cultivars improved yields when compared to moderately susceptible cultivars. By contrast, minimum yield differences were detected between Rps1k andRps1c genotypes, except in one environment. While a weak to moderate correlation was observed between CC and incidence of P. sojae symptomatic plants, a moderate to strong association was found between CC and yield. Across multiple environments, PRE herbicides chlorimuron-ethyl, metribuzin, saflufenacil, sulfentrazone, and flumioxazin had no impact on seedling root rot (disease severity index; DSI) when compared to the non-treated control. Similarly, no significant differences between PRE herbicides were detected on plant population, plant height, and yield. Community composition depicting primary pathogenic genera Fusarium, Phytophthora, Pythium, and Rhizoctonia did not occur at random but rather varied across environments and DSI classes. In two of the three environments, Phytophthorastructured approximately 22% of primary pathogenic genera, whereas, Rhizoctoniarecovery was low (