Pathotype Diversity of Phytophthora sojae in Eleven States in the United States

Pathotype diversity of Phytophthora sojae was assessed in 11 states in the United States during 2012 and 2013. Isolates of P. sojae were recovered from 202 fields, either from soil samples using a soybean seedling bioassay or by isolation from symptomatic plants. Each isolate was inoculated directly onto 12 soybean differentials; no Rps gene or Rps 1a, 1b, 1c, 1k, 3a, 3b, 3c, 4, 6, 7, or 8. There were 213 unique virulence pathotypes identified among the 873 isolates collected. None of the Rps genes were effective against all the isolates collected but Rps6 and Rps8 were effective against the majority of isolates collected in the northern regions of the sampled area. Virulence toward Rps1a, 1b, 1c, and 1k ranged from 36 to 100% of isolates collected in each state, while virulence to Rps6 and Rps8 was less than 36 and 10%, respectively. Depending on the state, the effectiveness of Rps3a ranged from totally effective to susceptible to more than 40% of the isolates. Pathotype complexity has increased in populations of P. sojae in the United States, emphasizing the increasing importance of stacked Rps genes in combination with high partial resistance as a means of limiting losses to P. sojae

Comparison of three microsatellite analysis methods for detecting genetic diversity in Phytophthora sojae (Stramenopila: Oomycete)

Analysis of an organism’s genetic diversity requires a method that gives reliable, reproducible results. Microsatellites are robust markers, however, detection of allele sizes can be difficult with some systems as well as consistency among laboratories. In this study, our two laboratories used 219 isolates of Phytophthora sojae to compare three microsatellite methods. Two capillary electrophoresis methods, the Applied Biosystems 3730 Genetic Analyzer and the CEQ 8000 Genetic Analysis system, detected an average of 2.4-fold more alleles compared to gel electrophoresis with a mean of 8.8 and 3.6 alleles per locus using capillary and gel methods, respectively. The two capillary methods were comparable, although allele sizes differed consistently by an average of 3.2 bp across isolates. Differences between capillary methods could be overcome if reference standard DNA genotypes are shared between collaborating laboratories

Integrated Management Strategies for Phytophthora sojae Combining Host Resistance and Seed Treatments

Phytophthora sojae has re-emerged as a serious soybean pathogen in the past decade. This may be due in part to changes in resistance levels in current cultivars, adoption of P. sojae populations to deployed Rps genes, and highly favorable environments in the past decade. This multilocation study evaluated the effect of seed treatments on the incidence and severity of Phytophthora root and stem rot on soybeans with different combinations of Rps genes and levels of partial resistance. The efficacy of the seed treatments was highly variable across locations. Seed treatments (metalaxyl and mefenoxam) provided protection and increased yields across cultivars in locations where rain or irrigation occurred shortly after planting (Ohio, South Dakota, and Ontario). However, there were no significant differences in stand or yield consistently across cultivars in Iowa, Nebraska, Wisconsin, or Ohio, where heavy precipitation did not occur until later growth stages. The environment, levels of inoculum, and pathogen complex may have played a role in the different responses to the seed treatments and to the different combinations of Rps genes and levels of partial resistance to P. sojae in the cultivars. Fields that are poorly drained and have P. sojae populations with complex pathotypes may benefit the most from seed treatments. Individual fields where producers may see the greatest benefit to utilizing these integrated management strategies will need to be identified

Pathogenic diversity of Phytophthora sojae pathotypes from Brazil.

Made available in DSpace on 2017-07-10T23:47:41Z (GMT). No. of bitstreams: 1 ID424682013v135n4p845EJPP.pdf: 260485 bytes, checksum: fcb10471d24ee2378596bb8eadf62b06 (MD5) Previous issue date: 2013-01-1

Phenotypic Characterization of a Major Quantitative Disease Resistance Locus for Partial Resistance to Phytophthora sojae

Major quantitative disease resistance loci (QDRLs) are rare in the Phytophthora sojae (Kaufmann and Gerdemann)–soybean [Glycine max (L). Merr.] pathosystem. A major QDRL on chromosome 18 (QDRL-18) was identified in PI 427105B and PI 427106. QDRL-18 represents a valuable resistance source for breeding programs. Thus, our objectives were to determine its isolate specificity and measure its effect on yield and resistance to both P. sojae and other soybean pathogens. We characterized near isogenic lines (NILs) developed from F7 recombinant inbred lines heterozygous at QDRL-18; NILs represent introgressions from PI 427105B, PI 427106, and susceptible ‘OX20- 8’. The introgressions from PI 427105B and PI 427106 increased resistance to P. sojae by 11 to 20% and 35 to 40%, respectively, based on laboratory and greenhouse assays, and increased yield by 13 to 29% under disease conditions. The resistant introgression from PI 427105B was also effective against seven P. sojae isolates with no isolate specificity detected. Based on quantitative polymerase chain reaction assays, NILs with the susceptible introgression had significantly higher relative levels of P. sojae colonization 48 h after inoculation. No pleiotropic effects for resistance to either soybean cyst nematode or Fusarium graminearum were detected. This information improves soybean breeders’ ability to make informed decisions regarding the deployment of QDRL-18 in their respective breeding programs

An Immunofluorescence Assay to Detect Urediniospores of \u3ci\u3ePhakopsora pachyrhizi\u3c/i\u3e

An indirect immunofluorescence spore assay (IFSA) was developed to detect urediniospores of Phakopsora pachyrhizi, utilizing rabbit polyclonal antisera produced in response to intact nongerminated (SBR1A) or germinated (SBR2) urediniospores of P. pachyrhizi. Both antisera were specific to Phakopsora spp. and did not react with other common soybean pathogens or healthy soybean leaf tissue in enzyme-linked immunosorbent assay (ELISA). SBR1A and SBR2 bound to P. pachyrhizi and P. meibomiae urediniospores were detected with goat anti-rabbit Alexa Fluor 488-tagged antiserum using a Leica DM IRB epifluorescent microscope with an I3 blue filter (excitation 450 to 490 nm, emission 515 nm). The assay was performed on standard glass microscope slides; double-sided tape was superior to a thin coating of petroleum jelly both in retaining spores and in immunofluorescence. The IFSA was used to confirm the identity of P. pachyrhizi urediniospores captured on glass slides from passive air samplers from Georgia, Kentucky, and Ohio during 2006

Attributes of context relevant to healthcare professionals' use of research evidence in clinical practice: a multi-study analysis

Background: To increase the likelihood of successful implementation of evidence-based practices, researchers, knowledge users, and healthcare professionals must consider aspects of context that promote and hinder implementation in their setting. The purpose of the current study was to identify contextual attributes and their features relevant to implementation by healthcare professionals and compare and contrast these attributes and features across different clinical settings and healthcare professional roles. Methods: We conducted a secondary analysis of 145 semi-structured interviews comprising 11 studies (10 from Canada and one from Australia) investigating healthcare professionals’ perceived barriers and enablers to their use of research evidence in clinical practice. The data was collected using semi-structured interview guides informed by the Theoretical Domains Framework across different healthcare professional roles, settings, and practices. We analyzed these data inductively, using constant comparative analysis, to identify attributes of context and their features reported in the interviews. We compared these data by (1) setting (primary care, hospital-medical/surgical, hospital-emergency room, hospital-critical care) and (2) professional role (physicians and residents, nurses and organ donor coordinators). Results: We identified 62 unique features of context, which we categorized under 14 broader attributes of context. The 14 attributes were resource access, work structure, patient characteristics, professional role, culture, facility characteristics, system features, healthcare professional characteristics, financial, collaboration, leadership, evaluation, regulatory or legislative standards, and societal influences. We found instances of the majority (n = 12, 86%) of attributes of context across multiple (n = 6 or more) clinical behaviors. We also found little variation in the 14 attributes of context by setting (primary care and hospitals) and professional role (physicians and residents, and nurses and organ donor coordinators). Conclusions: There was considerable consistency in the 14 attributes identified irrespective of the clinical behavior, setting, or professional role, supporting broad utility of the attributes of context identified in this study. There was more variation in the finer-grained features of these attributes with the most substantial variation being by setting

Comparison of Rps loci toward isolates, singly and combined inocula, of Phytophthora sojae in soybean PI 407985, PI 408029, PI 408097, and PI424477

For soybean, novel single dominant Resistance to Phytophthora sojae (Rps) genes are sought to manage Phytophthora root and stem rot. In this study, resistance to P. sojae was mapped individually in four recombinant inbred line (RIL) populations derived from crosses of the susceptible cultivar Williams with PI 407985, PI 408029, PI 408097, and PI424477 previously identified as putative novel sources of disease resistance. Each population was screened for resistance with five to seven isolates of P. sojae separately over multiple F7–F10 generations. Additionally, three of the populations were screened with inoculum from the combination of three P. sojae isolates (PPR), which comprised virulence to 14 Rps genes. Over 2,300 single-nucleotide polymorphism markers were used to construct genetic maps in each population to identify chromosomal regions associated with resistance to P. sojae. Resistance segregated as one or two genes to the individual isolates and one gene toward PPR in each population and mapped to chromosomes 3, 13, or 18 in one or more of the four RIL populations. Resistance to five isolates mapped to the same chromosome 3 region are as follows: OH7 (PI 424477 and PI408029), OH12168, OH7/8, PPR (PI 407985), and 1.S.1.1 (PI408029). The resistance regions on chromosome 13 also overlapped for OH1, OH25, OH-MIA (PI424477), PPR (PI 424477, PI 407985, and PI 408097), PPR and OH0217 (PI 408097), and OH4 (PI 408029), but were distinct for each population suggesting multiple genes confer resistance. Two regions were identified on chromosome 18 but all appear to map to known loci; notably, resistance to the combined inoculum (PPR) did not map at this locus. However, there are putative new alleles in three of four populations, three on chromosome 3 and two on chromosome 13 based on mapping location but also known virulence in the isolate used. This characterization of all the Rps genes segregating in these populations to these isolates will be informative for breeding, but the combined inoculum was able to map a novel loci. Furthermore, within each of these P. sojae isolates, there was virulence to more than the described Rps genes, and the effectiveness of the novel genes requires testing in larger populations