Variation and distribution of virulence phenotypes of <i> Bremia lactucae</i> in natural populations of <i>Lactuca serriola</i>

Lebeda, A.; Petrželová, I.

doi:10.1111/j.0032-0862.2004.01003.x

Cited by 38 publications

(26 citation statements)

References 24 publications

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“…The RGC2 cluster contains at least eight functional genes with different specificities against downy mildew caused by B. lactucae (Farrara et al 1987;Kesseli et al 1994). B. lactucae is present at least in temperate regions with L. serriola (Lebeda et al 2001;Lebeda and Petrželova 2004a;Petrzelova and Lebeda 2004), and it was prevalent in the collection sites in eastern Turkey (data not shown). A diverse RGC2 cluster is expected in a L. serriola population if a diverse population of B. lactucae is also present; however, comprehensive surveys of pathogens infecting natural populations of L. serriola are lacking.…”

Section: Discussionmentioning

confidence: 89%

Evolution and Genetic Population Structure of Prickly Lettuce (Lactuca serriola) and Its RGC2 Resistance Gene Cluster

et al. 2008

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Genetic structure and diversity of natural populations of prickly lettuce (Lactuca serriola) were studied using AFLP markers and then compared with the diversity of the RGC2 disease resistance gene cluster. Screening of 696 accessions from 41 populations using 319 AFLP markers showed that eastern Turkish and Armenian populations were the most diverse populations and might be located in the origin and center of diversity of L. serriola. Screening 709 accessions using the microsatellite MSATE6 that is located in the coding region of most RGC2 homologs detected 366 different haplotypes. Again, the eastern Turkish and Armenian populations had the highest diversities at the RGC2 cluster. The diversities at the RGC2 cluster in different populations were significantly correlated with their genomewide diversities. There was significant variation of copy number of RGC2 homologs in different populations, ranging from 12 to 22 copies per genome. The nucleotide diversities of two conserved lineages (type II) of RGC2 genes (K and L) were not correlated with diversities calculated using the MSATE6 or AFLP data. We hypothesize that the high genomewide diversity and diversity of the RGC2 cluster in eastern Turkish and Armenian populations resulted from high abiotic and biotic stresses in the regions of origin of L. serriola.

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Section: Discussionmentioning

confidence: 89%

Evolution and Genetic Population Structure of Prickly Lettuce (Lactuca serriola) and Its RGC2 Resistance Gene Cluster

et al. 2008

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“…For each isolate, the race and the two alleles at each derived genomic marker were indicated Table 3 continued Bremia lactucae (Lebeda and Petrzelova, 2004), and P. infestans (Andrivon, 1994). Although surprising at first sight, the importance of mutation greater than that of recombination in populations able to outcross may be related to the large number of clonal cycles of fungal multiplication during epidemics.…”

Section: Resultsmentioning

confidence: 99%

Emergence of new virulence in Plasmopara halstedii (sunflower downy mildew)

Sakr¹

2015

Acta Phytopathologica et Entomologica Hungarica

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The fast evolution of Plasmopara halstedii (downy mildew) remains a major risk for sunflower crop, as new races of the pathogen are bypassing the resistance of sunflower hybrids. In order to understand the processes which led a new virulence to appear in a local P. halstedii population, the genetic relationships were studied using 12 EST (Expressed Sequence Tag)-derived markers between five progeny isolates of races 300, 304, 314, 704 and 714 and two parental ones of races 100 and 710. All genetic analyses were carried out using five single zoosporangium isolates per P. halstedii isolate. There was no intra-isolate genetic variation among the seven pathogen isolates and five multilocus genotypes (MLG) were identified among the 35 P. halstedii single zoosporangium isolates. The single zoosporangium isolates of races 314, 704 and 714 had an intermediary genetic position between the single zoosporangium isolates of two parental isolates. The single zoosporangium isolates of three isolates of races 100, 300 and 304 were localized in the same genetic clade. Two genetic mechanisms could explain the emergence of new virulence in P. halstedii as a recombination between races and mutations in a clonal lineage.

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“…Crute 1987;Lebeda and Zinkernagel 2003a) and the same should be expected in the wild pathosystem, L. serriola-B. lactucae (Lebeda 2002;Lebeda and Petrželová 2004a;Petrželová and Lebeda 2004c). However, for L. serriola we still lack sufficient data about relevant pathogen populations in much of Europe except for the Czech Republic, hindering our understanding of coevolutionary trends within this pathosystem.…”

Section: Variation Of Resistance In Populations Of L Serriolamentioning

confidence: 88%

“…lactucae pathosystems has been the determination of virulence variation within B. lactucae populations, documenting its temporal and spatial dynamics, and comparing pathogen populations in crop (L. sativa) and wild (L. serriola) At the population level, virulence can be thought of as the average ability of a pathogen population to overcome the diversity of resistance genes present in the corresponding host population (Thrall and Burdon 2003). From this viewpoint, B. lactucae populations occurring naturally on L. serriola showed highly complex patterns of virulence in relation to the L. serriola and/or L. sativa differentials with resistance derived from L. serriola (Lebeda 2002;Lebeda and Petrželová 2004a;Petrželová and Lebeda 2004c). Such complexity of pathogen isolates may have its origin in response to the heterogeneity of the host populations (Bevan et al 1993), and it is supposed that, in gene-for-gene based pathosystems, broadly virulent isolates of pathogen are more likely to occur in highly diverse and resistant host populations (Thrall and Burdon 2003).…”

Section: Variation Of Resistance In Populations Of L Serriolamentioning

confidence: 99%

“…The most common wild host species of this pathogen is Lactuca serriola (prickly lettuce), and it can also be frequently found on Sonchus species Lebeda and Petrželová 2004a; Lebeda and Syrovátko 1988;Petrželová and Lebeda 2004b). However, it is well documented that B. lactucae is highly hostspecific and mostly limited to a single plant genus (Crute and Dixon 1981;Lebeda and Syrovátko 1988).…”

Section: Introductionmentioning

confidence: 99%

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Structure and variation in the wild-plant pathosystem: Lactuca serriola–Bremia lactucae

2008

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Over the past decade, extensive research on the wild-plant pathosystem, Lactuca serriola (prickly lettuce)-Bremia lactucae (lettuce downy mildew), has been conducted in the Czech Republic. Studies focused on pathogen occurrence and distribution, host range, variation in symptom expression and disease severity, interactions of B. lactucae with another fungal species (Golovinomyces cichoracearum) on L. serriola, variation in resistance within natural populations of L. serriola, the structure and dynamics of virulence within populations of B. lactucae, sexual reproduction of B. lactucae, and a comparison of virulence structure and changes in B. lactucae populations occurring in wild (L. serriola) and crop (L. sativa) pathosystems. The incidence of B. lactucae on naturally growing L. serriola and other Asteraceae was recorded. Lactuca serriola was the most commonly occurring host species, followed by Sonchus oleraceus. Over the duration of these studies, the incidence of B. lactucae in L. serriola populations varied between 45-87%. Disease incidence and disease prevalence were partly related to the size, density and different habitats of L. serriola populations. In addition to B. lactucae infection, infection by the lettuce powdery mildew fungus (Golovinomyces cichoracearum) was quite common, including coinfection. Variation in resistance to B. lactucae was studied by using ten isolates (NL and BL races with known virulence patterns) at a metapopulation level, i.e. 250 L. serriola samples representing 16 populations from the Czech Republic (CZ). Our comparisons revealed broad variation in host resistance among host populations and also intrapopulation variability. In the CZ populations, 45 resistance phenotypes were recorded, the most frequent were race-specific reaction patterns. Structural and temporal changes in virulence variation of B. lactucae populations on L. serriola were studied during 1998-2005. Altogether, 313 isolates of B. lactucae originating from the Czech Republic were examined for the presence of 32 virulence factors (v-factors), and 93 different virulence phenotypes (v-phenotypes) were recorded. A study of v-factor frequency showed that common vfactors in B. lactucae populations match some of the race-specific resistance genes/factors (Dm genes or Rfactors) originating from L. serriola. The highest frequency was recorded by v-factors v7, v11, 6, and 10) matching Dm genes originating from L. sativa were very rare. This demonstrates the close adaptation of B. lactucae virulence to the host (L. serriola) genetic background. Temporal changes in virulence frequencies over the period were recorded. In many vfactors (v11, v14, v16, and v25-28), fluctuations were Eur observed, some (v14 and v17) shifting to higher frequencies, and others (v5/8 and v23) decreasing. The occurrence of mating types was studied (1997)(1998)(1999) in a set of 59 B. lactucae isolates. Both compatibility types (B1 and B2) were recorded; however the majority of the isolates (96%) were type B2. A comparative study of B. lactucae vir...

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Variation and distribution of virulence phenotypes of Bremia lactucae in natural populations of Lactuca serriola

Cited by 38 publications

References 24 publications

Evolution and Genetic Population Structure of Prickly Lettuce (Lactuca serriola) and Its RGC2 Resistance Gene Cluster

Evolution and Genetic Population Structure of Prickly Lettuce (Lactuca serriola) and Its RGC2 Resistance Gene Cluster

Emergence of new virulence in Plasmopara halstedii (sunflower downy mildew)

Structure and variation in the wild-plant pathosystem: Lactuca serriola–Bremia lactucae

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