Download or read book Nature of Resistance of Soybeans to Phytophthora Root and Stem Rot written by William Louis Klarman and published by . This book was released on 1960 with total page 52 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 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 Identification and Characterization of Rate reducing Resistance to Phytophthora Megasperma F Sp Glycinea in Soybean written by Paul W. Tooley and published by . This book was released on 1982 with total page 334 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 Phytophthora Root and Stem Rot of Soybeans written by Robert F. Nyvall and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Functional Gene Analysis of Resistance QTL Towards Phytophthora Sojae on Soybean Chromosome 19 written by Anna K. Stasko and published by . This book was released on 2018 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phytophthora sojae is the causal agent of Phytophthora root and stem rot of soybean. One of the most effective disease management strategies against this pathogen is the use of resistant cultivars, primarily through single gene, Rps-mediated resistance. However, numerous populations of P. sojae have adapted to most Rps genes that are deployed in modern soybean cultivars, rendering them susceptible to this pathogen. Quantitative resistance, conferred by quantitative disease resistance loci (QDRL), offers an alternative to Rps-based resistance. Previous studies mapped two QDRL to chromosome 19 in the soybean cultivar Conrad, which has a high level of quantitative resistance. A recombinant inbred line (RIL) population derived from a cross of Conrad by Sloan (a moderately susceptible cultivar) used for mapping these QDRL was advanced to the F9:11 generation. This population was used to map/re-map the QDRL towards three isolates of P. sojae, and one isolate each of Pythium irregulare and Fusarium graminearum, using the SoySNP6K BeadChip for high-density marker genotyping. A total of ten, two, and three QDRL and suggestive QDRL were found that confer resistance to P. sojae, Py. irregulare, and F. graminearum, respectively. Individual QDRL explained 2-13.6% of the phenotypic variance (PV). One QDRL for both Py. irregulare and F. graminearum co-localized on chromosome 19. This resistance was contributed by Sloan and was juxtaposed to a QDRL for P. sojae with resistance contributed from Conrad. Alleles for resistance to different pathogens contributed from different parents in the same region, the number of unique QDRL for each pathogen, and the lack of correlation of resistance suggest that different mechanisms are involved in resistance towards these three pathogens. Interestingly, the QDRL located on chromosome 19 contained several genes related to auxin processes, which are known to contribute to susceptibility to several pathogens in Arabidopsis and may contribute to susceptibility of soybean to P. sojae. In this study, auxin metabolites were measured in P. sojae mycelia, media from P. sojae liquid cultures, and inoculated soybean roots. Auxin precursors were detected in the mycelia of P. sojae as well as the synthetic media. More importantly, auxin levels were significantly higher in inoculated roots than the mock controls in both resistant and susceptible genotypes at 48 hours after inoculation (hai). To examine the role of auxin transport in susceptibility to P. sojae, the nucleotide sequences and expression of root-related soybean auxin efflux transporters, GmPINs, were compared between Conrad and Sloan. There were sequence differences between the two cultivars; however, experimental variability prevented accurate detection of expression differences through a quantitative PCR approach. An auxin transport inhibitor and a synthetic auxin were applied to Conrad and Sloan to assess changes in infection of these cultivars with chemically altered auxin processes. As with the gene expression analysis, experimental variation prevented us from determining the exact effect of these treatments. Finally, several different approaches were used to begin developing a system for functional gene analysis, including composite plant-based hairy roots, cotyledon-based hairy roots, and virus-induced gene silencing (VIGS). Composite plant-based hairy roots were difficult to inoculate with P. sojae, Py. irregulare, and F. graminearum. Cotyledon-based hairy roots allowed for more consistent inoculation with P. sojae and expedited experimental testing of RNAi constructs targeting candidate genes. One of these constructs was able to reduce the expression of its target gene in three soybean genetic backgrounds. A Bean pod mottle virus (BPMV) VIGS vector used here moved systemically into soybean roots but was not effective at silencing candidate gene targets in this tissue. Future studies should continue to refine environmental/experimental conditions to reduce variation and develop a reliable method of assessing change in quantitative disease resistance to define the roles of candidate genes.

Download or read book Agronomic and Molecular Marker Mapping of Brown Stem Rot Phytophthora Root Rot and Powdery Mildew Resistance in Soybean written by David Glenn Lohnes and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Diseases are a major factor limiting the yield of soybean (Glycine max (L.) Merr.). Brown stem rot of soybean, caused by Phialophora gregata (Allington and Chamberlain) W. Gams, and phytophthora root rot, caused by Phytophthora sojae Kaufmann & Gerdemann, are major diseases of soybean in Illinois. A gene for resistance to powdery mildew, caused by Microsphaera diffusa Cke. & Pk., has also been found to be linked to a gene for phytophthora resistance. A field study was conducted to determine yield differences between isolines carrying different alleles at the locus for powdery mildew resistance, greenhouse experiments were performed to study the inheritance of brown stem rot resistance, and laboratory experiments were conducted in attempts to find molecular markers linked to brown stem rot, phytophthora, and powdery mildew resistance in soybean. When isolines carrying alleles for powdery mildew resistance are compared, the resistant isolines yielded 7% more than the adult-plant resistant isolines. With this yield advantage, it would be advantageous to use complete resistance to powdery mildew as a marker to select for phytophthora resistance in a soybean breeding program. Classification of reaction to brown stem rot of soybean populations indicates that a Clark isoline contains Rbs3, and that a germplasm line deriving resistance from PI 90.138 contains Rbs1 and another unknown resistance gene. Molecular marker analysis of Harosoy and a Harosoy brown stem rot isoline did not produce any polymorphic markers. Clark, Harosoy, and Williams were screened with several RAPD primers to determine the random amplified polymorphic DNA (RAPD) variability present between these cultivars. The percentage of RAPD products in common was 94% for Clark and Williams, 90% for Clark and Harosoy, and 84% for Harosoy and Williams. The material cost of running a single RAPD reaction ranged from 21 to 76 cents. Linkage analysis of the restriction fragment length polymorphism and disease classification revealed that the loci studied are in classical linkage group 19 and RFLP linkage group J, in the most likely order Rps2 Rmd Rj2 pA233 pA724 pK375. This is the most agronomically important gene-dense region of the soybean molecular map identified to date.

Download or read book Phytophthora Root and Stem Rot of Soybeans written by Robert F. Nyvall and published by . This book was released on 1979 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Phytophthora Root and Stem Rot of Soybeans written by Michigan State University. Cooperative Extension Service and published by . This book was released on 1981 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Residual Effects of Defeated Resistance Genes on Phytophthora Root Rot of Soybean written by Brian A. Young and published by . This book was released on 1989 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Soybean Phytophthora Root Rot written by Jose Cristino Melgar and published by . This book was released on 1997 with total page 122 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 Pathogen Specialization in Root Resistance in Soybean to Phytophthora Rot written by Hazel Avinell Joseph and published by . This book was released on 1991 with total page 110 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 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.