scholarly journals Population Diversity and Structure of Podosphaera macularis in the Pacific Northwestern United States and Other Populations

2020 ◽  
Vol 110 (5) ◽  
pp. 1105-1116
Author(s):  
David H. Gent ◽  
Briana J. Claassen ◽  
David M. Gadoury ◽  
Niklaus J. Grünwald ◽  
Brian J. Knaus ◽  
...  
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Population Diversity ◽  
Western United States ◽  
Wild Plants ◽  
Eastern United States ◽  
The Pacific ◽  
Differential Cultivars ◽  
Pathogen Populations ◽  
Podosphaera Macularis

Powdery mildew, caused by Podosphaera macularis, is one of the most important diseases of hop. The disease was first reported in the Pacific Northwestern United States, the primary hop-growing region in this country, in the mid-1990s. More recently, the disease has reemerged in newly planted hopyards of the eastern United States, as hop production has expanded to meet demands of local craft brewers. The spread of strains virulent on previously resistant cultivars, the paucity of available fungicides, and the potential introduction of the MAT1-2 mating type to the western United States, all threaten sustainability of hop production. We sequenced the transcriptome of 104 isolates of P. macularis collected throughout the western United States, eastern United States, and Europe to quantify genetic diversity of pathogen populations and elucidate the possible origins of pathogen populations in the western United States. Discriminant analysis of principal components grouped isolates within three to five geographic populations, dependent on stringency of grouping criteria. Isolates from the western United States were phenotyped and categorized into one of three pathogenic races based on disease symptoms generated on differential cultivars. Western U.S. populations were clonal, irrespective of pathogenic race, and grouped with isolates originating from Europe. Isolates originating from wild hop plants in the eastern United States were genetically differentiated from all other populations, whereas isolates from cultivated hop plants in the eastern United States mostly grouped with isolates originating from the west, consistent with origins from nursery sources. Mating types of isolates originating from cultivated western and eastern U.S. hop plants were entirely MAT1-1. In contrast, a 1:1 ratio of MAT1-1 and MAT1-2 was observed with isolates sampled from wild plants or Europe. Within the western United States a set of highly differentiated loci were identified in P. macularis isolates associated with virulence to the powdery mildew R-gene R6. The weight of genetic and phenotypic evidence suggests a European origin of the P. macularis populations in the western United States, followed by spread of the pathogen from the western United States to re-emergent production regions in the eastern United States. Furthermore, R6 compatibility appears to have been selected from an extant isolate within the western United States. Greater emphasis on sanitation measures during propagation and quarantine policies should be considered to limit further spread of novel genotypes of the pathogen, both between and within production areas.

Identification of Resistance to Powdery Mildew in Publicly Available Male Hop Germplasm

2018 ◽  
Vol 19 (3) ◽  
pp. 258-264
Author(s):  
David H. Gent ◽  
Briana J. Claassen ◽  
Megan C. Twomey ◽  
Sierra N. Wolfenbarger
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
R Genes ◽  
Sources Of Resistance ◽  
Department Of Agriculture ◽  
Breeding Programs ◽  
The Pacific ◽  
The U.S

Powdery mildew (caused by Podosphaera macularis) is one of the most important diseases of hop in the western United States. Strains of the fungus virulent on cultivars possessing the resistance factor termed R6 and the cultivar Cascade have become widespread in the Pacific Northwestern United States, the primary hop producing region in the country, rendering most cultivars grown susceptible to the disease at some level. In an effort to identify potential sources of resistance in extant germplasm, 136 male accessions of hop contained in the U.S. Department of Agriculture collection were screened under controlled conditions. Iterative inoculations with three isolates of P. macularis with varying race identified 23 (16.9%) accessions with apparent resistance to all known races of the pathogen present in the Pacific Northwest. Of the 23 accessions, 12 were resistant when inoculated with three additional isolates obtained from Europe that possess novel virulences. The nature of resistance in these individuals is unclear but does not appear to be based on known R genes. Identification of possible novel sources of resistance to powdery mildew will be useful to hop breeding programs in the western United States and elsewhere.

scholarly journals Distribution and Characterization of Podosphaera macularis Virulent on Hop Cultivars Possessing R6-Based Resistance to Powdery Mildew

Plant Disease ◽  
2016 ◽  
Vol 100 (6) ◽  
pp. 1212-1221 ◽  
Author(s):  
Sierra N. Wolfenbarger ◽  
Stephen T. Massie ◽  
Cynthia Ocamb ◽  
Emily B. Eck ◽  
Gary G. Grove ◽  
...  
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Mating Type ◽  
Resistance Genes ◽  
Severe Disease ◽  
The United States ◽  
Fitness Cost ◽  
Eastern United States ◽  
Host Genotype ◽  
Podosphaera Macularis

Host resistance, both quantitative and qualitative, is the preferred long-term approach for disease management in many pathosystems, including powdery mildew of hop (Podosphaera macularis). In 2012, an epidemic of powdery mildew occurred in Washington and Idaho on previously resistant cultivars whose resistance was putatively based on the gene designated R6. In 2013, isolates capable of causing severe disease on cultivars with R6-based resistance were confirmed in Oregon and became widespread during 2014. Surveys of commercial hop yards during 2012 to 2014 documented that powdery mildew is now widespread on cultivars possessing R6 resistance in Washington and Oregon, and the incidence of disease is progressively increasing. Pathogenic fitness, race, and mating type of R6-virulent isolates were compared with isolates of P. macularis lacking R6 virulence. All isolates were positive for the mating type idiomorph MAT1-1 and were able to overcome resistance genes Rb, R3, and R5 but not R1 or R2. In addition, R6-virulent isolates were shown to infect differential cultivars reported to possess the R6 gene and also the R4 gene, although R4 has not yet been broadly deployed in the United States. R6-virulent isolates were not detected from the eastern United States during 2012 to 2015. In growth chamber studies, R6-virulent isolates of P. macularis had a significantly longer latent period and produced fewer lesions on plants with R6 as compared with plants lacking R6, indicating a fitness cost to the fungus. R6-virulent isolates also produced fewer conidia when compared with isolates lacking R6 virulence, independent of whether the isolates were grown on a plant with or without R6. Thus, it is possible that the fitness cost of R6 virulence occurs regardless of host genotype. In field studies, powdery mildew was suppressed by at least 50% on plants possessing R6 as compared with those without R6 when coinoculated with R6-virulent and avirulent isolates. R6 virulence in P. macularis appears to be race specific and, at this time, imposes a measurable fitness penalty on the fungus. Resistance genes R1 and R2 appear to remain effective against R6-virulent isolates of P. macularis in the U.S. Pacific Northwest.

First Report of Powdery Mildew of Magnolia Caused by Microsphaera magnifica (Erysiphe magnifica) in the Pacific Northwest

2003 ◽  
Vol 4 (1) ◽  
pp. 37
Author(s):  
Dean A. Glawe
Keyword(s):  
United States ◽  
North America ◽  
Powdery Mildew ◽  
Pacific Northwest ◽  
Western United States ◽  
First Report ◽  
Landscape Plant ◽  
First Finding ◽  
The Pacific ◽  
First Time

Magnolia liliiflora Desrousseaux in Lamarck (orthographic variant: M. liliiflora), a species thought to have originated in China (3), is used as a landscape plant in North America. In August 2002, Microsphaera magnifica U. Braun was collected from three plants of M. liliiflora in the Magnolia collection at the Washington Park Arboretum, University of Washington, Seattle. This report documents for the first time a powdery mildew disease of a Magnolia species in the Pacific Northwest, and the first finding of M. magnifica in the western United States. Accepted for publication 14 April 2003. Published 12 May 2003.

scholarly journals A Climatology of 500-hPa Closed Lows in the Northeastern Pacific Ocean, 1948–2011

2014 ◽  
Vol 53 (6) ◽  
pp. 1578-1592 ◽  
Author(s):  
Nina S. Oakley ◽  
Kelly T. Redmond
Keyword(s):  
United States ◽  
Pacific Ocean ◽  
Interannual Variability ◽  
West Coast ◽  
The United States ◽  
Western United States ◽  
The West ◽  
Reanalysis Dataset ◽  
The Pacific ◽  
Northeastern Pacific

AbstractThe northeastern Pacific Ocean is a preferential location for the formation of closed low pressure systems. These slow-moving, quasi-barotropic systems influence vertical stability and sustain a moist environment, giving them the potential to produce or affect sustained precipitation episodes along the west coast of the United States. They can remain motionless or change direction and speed more than once and thus often pose difficult forecast challenges. This study creates an objective climatological description of 500-hPa closed lows to assess their impacts on precipitation in the western United States and to explore interannual variability and preferred tracks. Geopotential height at 500 hPa from the NCEP–NCAR global reanalysis dataset was used at 6-h and 2.5° × 2.5° resolution for the period 1948–2011. Closed lows displayed seasonality and preferential durations. Time series for seasonal and annual event counts were found to exhibit strong interannual variability. Composites of the tracks of landfalling closed lows revealed preferential tracks as the features move inland over the western United States. Correlations of seasonal event totals for closed lows with ENSO indices, the Pacific decadal oscillation (PDO), and the Pacific–North American (PNA) pattern suggested an above-average number of events during the warm phase of ENSO and positive PDO and PNA phases. Precipitation at 30 U.S. Cooperative Observer stations was attributed to closed-low events, suggesting 20%–60% of annual precipitation along the West Coast may be associated with closed lows.

scholarly journals Evaluation of Seven Complex Pennisetum Hybrids for Container and Landscape Performance in the Pacific Northwestern United States

2013 ◽  
Vol 23 (4) ◽  
pp. 525-528 ◽  
Author(s):  
Ryan N. Contreras ◽  
Jim Owen ◽  
Wayne Hanna ◽  
Brian Schwartz
Keyword(s):  
United States ◽  
Growth Form ◽  
Field Performance ◽  
Eastern United States ◽  
Randomized Experiments ◽  
Climatic Regions ◽  
The Pacific ◽  
Wide Range ◽  
Complex Hybrid ◽  
Market Preference

Ornamental grasses such as fountaingrass or napiergrass, collectively called pennisetums, belong to the genus Pennisetum, which is a diverse genus with over 80 species adapted to a wide range of climatic regions and known for its drought tolerance. Breeding efforts have led to improvements such as more intense purple foliage color, disease resistance, and apparent sterility. These improved forms have been developed and tested in the eastern United States. The objective of this research was to evaluate container and field performance of seven new complex hybrid pennisetums in the Pacific northwestern United States. Two completely randomized experiments with three replications were conducted over 2 years (2010 and 2011) at two locations. We selected seven trispecific hybrid pennisetums resulting from interploid and interspecific crossing that were given accessions Tift 5, Tift 6, Tift 10, Tift 11, Tift, 13, Tift 15, and Tift 26. Experiment 1 evaluated container performance in Corvallis, OR, while Expt. 2 evaluated field performance in Aurora, OR. Size index (SI), growth form rating, and color rating were collected and analyzed separately by location. In the container study, significant differences were observed among selections for growth form in 2010 and color ratings in both 2010 and 2011. In 2010, Tift 6, Tift 11, Tift 13, and Tift 15 had the highest growth form rating. For color rating, Tift 5, Tift 10, and Tift 26 were among the four highest rated selections in both years. In the field study, Tift 5, Tift 10, Tift 11, and Tift 26 had the highest SI when data were pooled over the 2 years, but all selections reached acceptable size for landscape use during both years of the study. Similarly, there were color differences among selections with Tift 5, Tift 10, Tift 15, and Tift 26 being highest rated. None of the selections survived below winter temperatures of −5 °C at either location during either year of the study. Our evaluations indicate that these selections have potential in the Pacific northwestern United States as annuals. Differences in complex hybrid pennisetums were observed in SI, growth form rating, and color rating. These differences demonstrated the variation among selections and will allow producers to choose desired traits based on market preference.

A comparison of earthquake damage areas as a function of magnitude across the United States

1993 ◽  
Vol 83 (4) ◽  
pp. 1064-1080 ◽  
Author(s):  
G. A. Bollinger ◽  
M. C. Chapman ◽  
M. S. Sibol
Keyword(s):  
United States ◽  
North America ◽  
Ground Motion ◽  
Epicentral Distance ◽  
The United States ◽  
Western United States ◽  
Eastern North America ◽  
Similar Response ◽  
Eastern United States ◽  
The West

Abstract This study investigates the relationship between earthquake magnitude and the size of damage areas in the eastern and western United States. To quantify damage area as a function of moment magnitude (M), 149 MMI VI and VII areas for 109 earthquakes (88 in the western United States, 21 in the eastern United States and Canada) were measured. Regression of isoseismal areas versus M indicated that areas in the East were larger than those in the West, at both intensity levels, by an average 5 × in the M 4.5 to 7.5 range. In terms of radii for circles of equivalent area, these results indicate that damaging ground motion from shocks of the same magnitude extend 2 × the epicentral distance in eastern North America compared to the West. To determine source and site parameters consistent with the above results, response spectral levels for eastern North America were stochastically simulated and compared with response spectral ordinates derived from recorded strong ground motion data in the western United States. Stress-drop values of 200 bars, combined with a surficial 2-km-thick low velocity “sedimentary” layer over rock basement, produced results that are compatible with the intensity observations, i.e., similar response spectral levels in the east at approximately twice their epicentral distance in the western U.S. distance. These results suggest that ground motion modeling in eastern North America may need to incorporate source and site parameters different from those presently in general use. The results are also of importance to eastern U.S. hazard assessments as they require allowance for the larger damage areas in preparedness and mitigation programs.

scholarly journals Coherence between the Great Salt Lake Level and the Pacific Quasi-Decadal Oscillation

2010 ◽  
Vol 23 (8) ◽  
pp. 2161-2177 ◽  
Author(s):  
Shih-Yu Wang ◽  
Robert R. Gillies ◽  
Jiming Jin ◽  
Lawrence E. Hipps
Keyword(s):  
United States ◽  
Great Basin ◽  
Lake Level ◽  
Salt Lake ◽  
Western United States ◽  
Water Vapor Flux ◽  
Vapor Flux ◽  
The Pacific ◽  
Circulation Patterns ◽  
Precipitation Variation

Abstract The lake level elevation of the Great Salt Lake (GSL), a large closed basin lake in the arid western United States, is characterized by a pronounced quasi-decadal oscillation (QDO). The variation of the GSL elevation is very coherent with the QDO of sea surface temperature anomalies in the tropical central Pacific (also known as the Pacific QDO). However, such coherence denies any direct association between the precipitation in the GSL watershed and the Pacific QDO because, in a given frequency, the precipitation variation always leads the GSL elevation variation. Therefore, the precipitation variation is phase shifted from the Pacific QDO. This study investigates the physical mechanism forming the coherence between the GSL elevation and the Pacific QDO. Pronounced and coherent quasi-decadal signals in precipitation, streamflow, water vapor flux, and drought conditions are found throughout the Great Basin. Recurrent atmospheric circulation patterns develop over the Gulf of Alaska during the warm-to-cool and cool-to-warm transition phases of the Pacific QDO. These circulation patterns modulate the water vapor flux associated with synoptic transient activities over the western United States and, in turn, lead to the QDO in the hydrological cycle of the Great Basin. As the GSL integrates the hydrological responses in the Great Basin, the hydrological QDO is then transferred to the GSL elevation. Because the GSL elevation consistently lags the precipitation by a quarter-phase (about 3 yr in the quasi-decadal time scale), these processes take an average of 6 yr for the GSL elevation to eventually respond to the Pacific QDO. This creates a half-phase delay of the GSL elevation from the Pacific QDO, thereby forming the inverse, yet coherent, relationship between them. Tree-ring reconstructed precipitation records confirm that the quasi-decadal signal in precipitation is a prominent feature in this region.

scholarly journals Contrasting Patterns of Genetic Diversity and Population Structure of Armillaria mellea sensu stricto in the Eastern and Western United States

2010 ◽  
Vol 100 (7) ◽  
pp. 708-718 ◽  
Author(s):  
Kendra Baumgartner ◽  
Renaud Travadon ◽  
Johann Bruhn ◽  
Sarah E. Bergemann
Keyword(s):  
United States ◽  
Genetic Diversity ◽  
Population Structure ◽  
Los Angeles ◽  
The United States ◽  
Sensu Stricto ◽  
Western United States ◽  
Eastern United States ◽  
Armillaria Mellea ◽  
Genetic Pools

Armillaria mellea infects hundreds of plant species in natural and managed ecosystems throughout the Northern hemisphere. Previously reported nuclear genetic divergence between eastern and western U.S. isolates is consistent with the disjunct range of A. mellea in North America, which is restricted mainly to both coasts of the United States. We investigated patterns of population structure and genetic diversity of the eastern (northern and southern Appalachians, Ozarks, and western Great Lakes) and western (Berkeley, Los Angeles, St. Helena, and San Jose, CA) regions of the United States. In total, 156 diploid isolates were genotyped using 12 microsatellite loci. Absence of genetic differentiation within either eastern subpopulations (θST = –0.002, P = 0.5 ) or western subpopulations (θST = 0.004, P = 0.3 ) suggests that spore dispersal within each region is sufficient to prevent geographic differentiation. In contrast to the western United States, our finding of more than one genetic cluster of isolates within the eastern United States (K = 3), revealed by Bayesian assignment of multilocus genotypes in STRUCTURE and confirmed by genetic multivariate analyses, suggests that eastern subpopulations are derived from multiple founder sources. The existence of amplifiable and nonamplifiable loci and contrasting patterns of genetic diversity between the two regions demonstrate that there are two geographically isolated, divergent genetic pools of A. mellea in the United States.

scholarly journals Boundary-Included Enhanced Water Storage Changes Inferred by GPS in the Pacific Rim of the Western United States

2020 ◽  
Vol 12 (15) ◽  
pp. 2429
Author(s):  
Yingchun Shen ◽  
Haoming Yan ◽  
Peng Peng ◽  
Wei Feng ◽  
Zizhan Zhang ◽  
...  
Keyword(s):  
United States ◽  
Variance Reduction ◽  
Water Storage ◽  
Pacific Rim ◽  
Western United States ◽  
Vertical Deformation ◽  
Inversion Model ◽  
The Pacific ◽  
Terrestrial Water ◽  
The One

We developed a new boundary-included inversion model to improve the terrestrial water storage (TWS) inverted from regional GPS vertical deformation data. Through defining a new disc load empirical function (DLEF) and considering the mass change effect from the near but outside region, the result shows the TWS is more reasonable than the one inverted directly. Six simulation tests further confirmed the effectiveness of the boundary-included model. Finally, our new boundary-included model was used to derive the TWS in the Pacific Rim of the western United States based on the GPS-observed vertical deformation information. The inversion results show that our boundary-included inversion model can effectively improve the inversion results by 10–20% in terms of variance reduction in the boundary regions.

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