scholarly journals Host ecotype generates evolutionary and epidemiological divergence across a pathogen metapopulation

2014 ◽  
Vol 281 (1787) ◽  
pp. 20140522 ◽  
Author(s):  
Anna-Liisa Laine ◽  
Jeremy J. Burdon ◽  
Adnane Nemri ◽  
Peter H. Thrall
Keyword(s):  
Host Resistance ◽  
Population Genetic ◽  
Host Population ◽  
Heterogeneous Environments ◽  
Evolutionary Potential ◽  
Pathogen Population ◽  
Melampsora Lini ◽  
Close Proximity ◽  
Pathogen Populations ◽  
Inoculation Study

The extent and speed at which pathogens adapt to host resistance varies considerably. This presents a challenge for predicting when—and where—pathogen evolution may occur. While gene flow and spatially heterogeneous environments are recognized to be critical for the evolutionary potential of pathogen populations, we lack an understanding of how the two jointly shape coevolutionary trajectories between hosts and pathogens. The rust pathogen Melampsora lini infects two ecotypes of its host plant Linum marginale that occur in close proximity yet in distinct populations and habitats. In this study, we found that within-population epidemics were different between the two habitats. We then tested for pathogen local adaptation at host population and ecotype level in a reciprocal inoculation study. Even after controlling for the effect of spatial structure on infection outcome, we found strong evidence of pathogen adaptation at the host ecotype level. Moreover, sequence analysis of two pathogen infectivity loci revealed strong genetic differentiation by host ecotype but not by distance. Hence, environmental variation can be a key determinant of pathogen population genetic structure and coevolutionary dynamics and can generate strong asymmetry in infection risks through space.

Virulence dynamics in Puccinia graminis f.sp. avenae in Canada

1979 ◽  
Vol 57 (8) ◽  
pp. 952-957 ◽  
Author(s):  
J. W. Martens ◽  
R. I. H. McKenzie
Keyword(s):  
Host Resistance ◽  
Gradual Increase ◽  
Host Population ◽  
Early Years ◽  
Puccinia Graminis ◽  
Pathogen Population ◽  
Eastern Canada ◽  
The West ◽  
Susceptible Host ◽  
Pathogen Populations

Virulence in Puccinia graminis f.sp. avenue has been studied in Canada since 1921. Changes in host resistance, the succession of avirulence–virulence combinations, and changes in the composition of the pathogen population during the ensuing 57 years are presented graphically and indicate that the organism is highly dynamic even when the host population is relatively static. The early years are characterized by the presence of races virulent only on the universally susceptible host or cultivars with a single resistance gene followed by a gradual increase in virulence beginning in 1943 and a differentiation of eastern and western pathogen populations. By 1950 the zero- and one-gene virulence races were being displaced by Pg-1, -2 and Pg-1, -2, -3 virulence combinations in eastern Canada, an event that did not occur in the west until 1961. The latter period was characterized by the combining of virulence on all resistance genes except Pg-8 and Pg-13 in the east and Pg-9 and Pg-13 in the west. Virulence on resistance conferred by gene Pg-13 is still rare.

scholarly journals Variable opportunities for outcrossing result in hotspots of novel genetic variation in a pathogen metapopulation

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Anna-Liisa Laine ◽  
Benoit Barrès ◽  
Elina Numminen ◽  
Jukka P Siren
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Structure ◽  
Fungal Pathogen ◽  
Population Genetic ◽  
Reproductive Strategies ◽  
Natural Populations ◽  
Pathogen Population ◽  
To Come ◽  
Pathogen Populations

Many pathogens possess the capacity for sex through outcrossing, despite being able to reproduce also asexually and/or via selfing. Given that sex is assumed to come at a cost, these mixed reproductive strategies typical of pathogens have remained puzzling. While the ecological and evolutionary benefits of outcrossing are theoretically well-supported, support for such benefits in pathogen populations are still scarce. Here, we analyze the epidemiology and genetic structure of natural populations of an obligate fungal pathogen, Podosphaera plantaginis. We find that the opportunities for outcrossing vary spatially. Populations supporting high levels of coinfection –a prerequisite of sex – result in hotspots of novel genetic diversity. Pathogen populations supporting coinfection also have a higher probability of surviving winter. Jointly our results show that outcrossing has direct epidemiological consequences as well as a major impact on pathogen population genetic diversity, thereby providing evidence of ecological and evolutionary benefits of outcrossing in pathogens.

scholarly journals Population Genetic Divergence and Environment Influence the Gut Microbiome in Oregon Threespine Stickleback

Genes ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 484 ◽  
Author(s):  
Steury ◽  
Currey ◽  
Cresko ◽  
Bohannan
Keyword(s):  
Gut Microbiome ◽  
Genetic Divergence ◽  
Population Genetic ◽  
Host Population ◽  
Threespine Stickleback ◽  
Wild Host ◽  
Microbiome Research ◽  
Host Genetic ◽  
Combine Population ◽  
Natural Ecology

Much of animal-associated microbiome research has been conducted in species for which little is known of their natural ecology and evolution. Microbiome studies that combine population genetic, environment, and geographic data for wild organisms can be very informative, especially in situations where host genetic variation and the environment both influence microbiome variation. The few studies that have related population genetic and microbiome variation in wild populations have been constrained by observation-based kinship data or incomplete genomic information. Here we integrate population genomic and microbiome analyses in wild threespine stickleback fish distributed throughout western Oregon, USA. We found that gut microbiome diversity and composition partitioned more among than within wild host populations and was better explained by host population genetic divergence than by environment and geography. We also identified gut microbial taxa that were most differentially abundant across environments and across genetically divergent populations. Our findings highlight the benefits of studies that investigate host-associated microbiomes in wild organisms.

scholarly journals Grafting for Disease Resistance

HortScience ◽  
2008 ◽  
Vol 43 (6) ◽  
pp. 1673-1676 ◽  
Author(s):  
Stephen R. King ◽  
Angela R. Davis ◽  
Wenge Liu ◽  
Amnon Levi
Keyword(s):  
Disease Resistance ◽  
Root Rot ◽  
Pathogen Resistance ◽  
Soilborne Pathogens ◽  
Pathogen Population ◽  
Soil Fumigant ◽  
Soil Microbial ◽  
The Future ◽  
Microbial Environment ◽  
Pathogen Populations

The primary purpose of grafting vegetables worldwide has been to provide resistance to soilborne diseases. The potential loss of methyl bromide as a soil fumigant combined with pathogen resistance to commonly used pesticides will make resistance to soilborne pathogens even more important in the future. The major disease problems addressed by grafting include fusarium wilt, bacterial wilt, verticillium wilt, monosporascus root rot, and nematodes. Grafting has also been shown in some instances to increase tolerance to foliar fungal diseases, viruses, and insects. If the area devoted to grafting increases in the future, there will likely be a shift in the soil microbial environment that could lead to the development of new diseases or changes in the pathogen population of current diseases. This shift in pathogen populations could lead to the development of new diseases or the re-emergence of previously controlled diseases. Although grafting has been demonstrated to control many common diseases, the ultimate success will likely depend on how well we monitor for changes in pathogen populations and other unexpected consequences.

Variation in pathogenicity among and within Mycosphaerella pinodes populations collected from field pea in Australia

1998 ◽  
Vol 76 (11) ◽  
pp. 1955-1966 ◽  
Author(s):  
J M Wroth
Keyword(s):  
Cluster Analysis ◽  
Pisum Sativum ◽  
Host Resistance ◽  
Ascochyta Blight ◽  
Mycosphaerella Pinodes ◽  
Environment Interaction ◽  
Pathogen Population ◽  
Host Genotype ◽  
Host Pathogen Interaction ◽  
The Relationship

Ninety-nine single ascospore isolates of Mycosphaerella pinodes (Berk. & Blox.) Vestergr. from widely separated locations in southern Australia varied greatly in their ability to cause disease in leaves and stems of 10 host genotypes when assayed at two inoculum pressures. There were highly significant differences between the infection pressures, isolates, and host genotypes that accounted for most of the variance. A small proportion of the variance included a highly significant host genotype beta isolate interactions in leaves and stems and a highly significant host genotype beta isolate beta environment interaction in leaves. The continuous variation in disease responses among isolates precluded classification into distinct pathotypes. A cluster analysis of the data revealed that many isolates were closely related irrespective of the host cultivar or location from which they were collected. The relationship between mean host resistance and the variation among isolates was assessed, and it was concluded that increasing host resistance was unlikely to increase variation in the pathogen population; therefore, resistance should be relatively stable.Key words: Ascochyta blight, Pisum sativum, host-pathogen interaction, cluster analysis.

Puccinia striiformis in Australia: a review of the incursion, evolution, and adaptation of stripe rust in the period 1979 - 2006

2007 ◽  
Vol 58 (6) ◽  
pp. 567 ◽  
Author(s):  
C. R. Wellings
Keyword(s):  
Stripe Rust ◽  
Chemical Control ◽  
Puccinia Striiformis ◽  
Cool Temperature ◽  
Pathogen Population ◽  
European Origin ◽  
Yield And Quality ◽  
Eastern Australia ◽  
Major Shift ◽  
Pathogen Populations

The wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici; Pst) was first detected in Australia in 1979. The features of the initial pathotype suggested that it was of European origin, and later work provided evidence that it was most likely transmitted as adherent spores on travellers’ clothing. Despite long-held views that this cool temperature pathogen would not adapt to Australian conditions, Pst became endemic and progressively adapted to commercial wheat production through step-wise mutation. Several of these mutant pathotypes became frequent in the Pst population, causing widespread infection and significant costs to production (yield and quality losses; chemical control expenditure) in certain cultivars and seasons. Pathotype evolution, including adaptation to native barley grass (Hordeum spp.) populations, is described. The occurrence of an exotic pathotype of Pst in Western Australia in 2002, and its subsequent spread to eastern Australia, represented a major shift in the pathogen population. This pathotype dominated pathogen populations throughout Australia from 2003, with chemical control expenditure estimated at AU$40–90 million annually. Another exotic introduction was detected in 1998. Initial data indicated that certain isolates collected from barley grass were highly avirulent to wheat differentials, with the exception of partial virulence to Chinese 166. Further seedling tests revealed that these isolates, tentatively designated barley grass stripe rust (BGYR), were virulent on several Australian barleys, notably those of Skiff parentage. Data, including molecular studies, suggest that BGYR is a new forma specialis of P. striiformis. Field nurseries indicate that BGYR is likely to have little impact on commercial barley, although this may change with further pathotype evolution or the release of susceptible cultivars.

scholarly journals Results of monitoring of the population of Blumeria graminis f.sp. hordei in Latvia in 2009-2010

2012 ◽  
Vol 66 (1-2) ◽  
pp. 41-47
Author(s):  
Inese Kokina ◽  
Isaak Rashal
Keyword(s):  
Blumeria Graminis ◽  
Shannon Index ◽  
Simpson Index ◽  
Pathogen Population ◽  
Random Samples ◽  
Barley Powdery Mildew ◽  
North Eastern ◽  
Pathogen Populations ◽  
North Western ◽  
High Diversity

Results of monitoring of the population ofBlumeria graminisf.sp.hordeiin Latvia in 2009-2010In 2009-2010, random samples of the causal agent of barley powdery mildew were collected in Daugavpils (south-eastern Latvia, Latgale region), Stende (north-western Latvia, Kurzeme region) and Priekuļi (north-eastern Latvia, Vidzeme region). Virulence frequency, complexity and pathotypes were calculated in the pathogen populations. Significant differences of virulence detected by the genesVa1, Va3and Va13occurred among samples of the pathogen population collected in different parts of Latvia. Nei index, Müller's index, Kosman index, Shannon index and Simpson index showed considerably higher diversity in Daugavpils and Stende during 2009-2010. In Daugavpils, the population ofBlumeria graminisf.sp.hordei was particularly characterised by high diversity.

scholarly journals Host community structure and the maintenance of pathogen diversity

2007 ◽  
Vol 274 (1619) ◽  
pp. 1715-1721 ◽  
Author(s):  
Caroline Buckee ◽  
Leon Danon ◽  
Sunetra Gupta
Keyword(s):  
Community Structure ◽  
Spatial Differentiation ◽  
Host Community ◽  
Contact Network ◽  
Strong Mixing ◽  
Metapopulation Model ◽  
Pathogen Population ◽  
Antigenic Diversity ◽  
Pathogen Diversity ◽  
Pathogen Populations

Community structure has been widely identified as a feature of many real-world networks. It has been shown that the antigenic diversity of a pathogen population can be significantly affected by the contact network of its hosts; however, the effects of community structure have not yet been explored. Here, we examine the congruence between patterns of antigenic diversity in pathogen populations in neighbouring communities, using both a deterministic metapopulation model and individual-based formulations. We show that the spatial differentiation of the pathogen population can only be maintained at levels of coupling far lower than that necessary for the host populations to remain distinct. Therefore, identifiable community structure in host networks may not reflect differentiation of the processes occurring upon them and, conversely, a lack of genetic differentiation between pathogens from different host communities may not reflect strong mixing between them.

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