23 research outputs found
A Fresh Look at Grape Powdery Mildew (Erysiphe necator) A and B Genotypes Revealed Frequent Mixed Infections and Only B Genotypes in Flag Shoot Samples
Erysiphe necator populations, causing powdery mildew of grapes, have a complex genetic structure. Two genotypes, A and B, were identified in most vineyards across the world on the basis of fixed single nucleotide polymorphisms (SNPs) in several DNA regions. It was hypothesized that A populations overwinter as mycelia in grapevine buds, giving rise to so-called flag shoots in spring, and are more sensitive to fungicides than B populations, which overwinter as ascospores and become widespread later in the season. Other studies concluded that the biological significance of these genotypes is unclear. In the spring of 2015, there was a unique opportunity to collect E. necator samples from flag shoots in Hungary. The same grapevines were sampled in summer and autumn as well. A total of 182 samples were genotyped on the basis of beta-tubulin (TUB2), nuclear ribosomal DNA (nrDNA) intergenic spacer (IGS), and internal transcribed spacer (ITS) sequences. Genotypes of 56 samples collected in 2009-2011 were used for comparison. Genotype A was not detected at all in spring, and was present in only 19 samples in total, mixed with genotype B, and sometimes with another frequently found genotype, designated as B2. These results did not support the hypothesis about temporal isolation of the two genotypes and indicated that these are randomly distributed in vineyards
A hyperparasite affects the population dynamics of a wild plant pathogen
Assessing the impact of natural enemies of plant and animal pathogens on their host’s
population dynamics is needed to determine the role of hyperparasites in affecting
disease dynamics, and their potential for use in efficient control strategies of patho-
gens. Here, we focus on the long-term study describing metapopulation dynamics of
an obligate pathogen, the powdery mildew (
Podosphaera plantaginis
) naturally infect-
ing its wild host plant (
Plantago lanceolata
) in the fragmented landscape of the
�
Aland
archipelago (southwest Finland). Regionally, the pathogen persists through a balance
of extinctions and colonizations, yet factors affecting extinction rates remain poorly
understood. Mycoparasites of the genus
Ampelomyces
appear as good candidates for
testing the role of a hyperparasite, i.e. a parasite of other parasites, in the regulation of
their fungal hosts’ population dynamics. For this purpose, we first designed a quantita-
tive PCR assay for detection of
Ampelomyces
spp. in field-collected samples. This
newly developed molecular test was then applied to a large-scale sampling within the
�
Aland archipelago, revealing that
Ampelomyces
is a widespread hyperparasite in this
system, with high variability in prevalence among populations. We found that the
hyperparasite was more common on leaves where multiple powdery mildew strains
coexist, a pattern that may be attributed to differential exposure. Moreover, the preva-
lence of
Ampelomyces
at the plant level negatively affected the overwinter survival of
its fungal host. We conclude that this hyperparasite may likely impact on its host pop-
ulation dynamics and argue for increased focus on the role of hyperparasites in disease
dynamics
Két hazai kétéltűfaj kitridiomikózissal szembeni fogékonysága és érzékenysége
A kétéltűeket veszélyeztető kitridiomikózis kórokozója, a Batrachochytrium dendrobatidis (Bd; Longcore, Pessier & D. K. Nichols, 1999) nevű gombafaj bizonyítottan jelen van a Kárpát-medencében is, ugyanakkor a számlájára írható drasztikus állománycsökkenést itt ez idáig nem tapasztaltunk. Ennek egyik oka lehet a honos populációk magas toleranciája a betegséggel szemben. Kísérletünkben barna varangy és erdei béka ebihalait fertőztük egy magas virulenciájú Bd törzzsel. A gomba egyik fajnál sem csökkentette a túlélést, a fejlődési sebességet és az átalakulás utáni tömeget. Ugyanakkor a barna varangy egyedeknél az erdei békáknál mért fertőzöttség sokszorosát figyeltük meg. Úgy tűnik, hogy a hazai barna varangy populációk magas toleranciával, az erdei béka populációk pedig magas rezisztenciával rendelkeznek a betegséggel szemben
The Parauncinula polyspora Draft Genome Provides Insights into Patterns of Gene Erosion and Genome Expansion in Powdery Mildew Fungi
Improved DNA extraction and quantitative real-time PCR for genotyping Erysiphe necator and detecting the DMI fungicide resistance marker A495T, using single ascocarps
DNA extraction from minute fungal samples is challenging in all genetic studies. Identification of genetic groups and population biology mostly rely on the laborious production of single conidium isolates or on field samples, including infected plant materials. This paper reports a simple and cost-effective protocol for DNA extraction from individual chasmothecia of Erysiphe necator for subsequent applications. It is a less laborious alternative for genotyping purposes than production and analysis of single conidium isolates or analysis of infected plant material from the field. Using the protocols described here for 186 E. necator samples tested, genetic groups A and B were assigned. Based on CYP51 sequences, all the samples belonged to group B, while TUB2 sequences exhibited SNPs also diagnostic for group A. Additionally, a quantitative real-time PCR detection method of single nucleotide polymorphism in the CYP51 gene associated with DMI fungicide resistance was applied. The A495T marker, associated with DMI resistance, and here reported for the first time from Hungary, was detected by quantitative real-time PCR assays and direct sequencing of CYP51. The methods developed in this study can be applied as routine tests to monitor powdery mildew populations for fungicide resistance and other genetic characteristics
Beyond Nuclear Ribosomal DNA Sequences: Evolution, Taxonomy, and Closest Known Saprobic Relatives of Powdery Mildew Fungi (Erysiphaceae) Inferred from Their First Comprehensive Genome-Scale Phylogenetic Analyses
A növénykórokozó gombák DMI-fungicidekkel szembeni rezisztenciájának molekuláris biológiai háttere = The Molecular Biological Background of DMI Fungicide Resistance in Plant Pathogenic Fungi
Niche differentiation within a cryptic pathogen complex: climatic drivers and hyperparasitism at multiple spatial scales
Deciphering the biology of Cryptophyllachora eurasiatica gen. et sp nov., an often cryptic pathogen of an allergenic weed, Ambrosia artemisiifolia
A little known, unculturable ascomycete, referred to as Phyllachora ambrosiae, can destroy the inflorescences of Ambrosia artemisiifolia, an invasive agricultural weed and producer of highly allergenic pollen. The fungus often remains undetectable in ragweed populations. This work was conducted to understand its origin and pathogenesis, a prerequisite to consider its potential as a biocontrol agent. The methods used included light and transmission electron microscopy, nrDNA sequencing, phylogenetic analyses, artificial inoculations, and the examination of old herbarium and recent field specimens from Hungary, Korea, Ukraine and USA. The Eurasian and the North American specimens of this fungus were to represent two distinct, although closely related lineages that were only distantly related to other lineages within the Ascomycota. Consequently, we describe a new genus that includes Cryptophyllachora eurasiatica gen. et sp. nov. and C. ambrosiae comb. nov., respectively. The pathogenesis of C. eurasiatica was shown in A. artemisiifolia. No evidence was found for either seed-borne transmission or systemic infection. Two hypotheses were developed to explain the interaction between C. eurasiatica and A. artemisiifolia: (i) as yet undetected seed-borne transmissions and latent, systemic infections; or (ii) alternative hosts
Exposure to Batrachochytrium dendrobatidis affects chemical defences in two anuran amphibians, Rana dalmatina and Bufo bufo
BACKGROUND: Batrachochytrium dendrobatidis (Bd) is the causative agent of chytridiomycosis, one of the major causes of worldwide amphibian biodiversity loss. Many amphibians exhibit skin-based chemical defences, which may play an important role against invading pathogens, but whether the synthesis of these chemical compounds is enhanced or suppressed in the presence of pathogens is largely unknown. Here we investigated direct and indirect effects of larval exposure to the globally distributed and highly virulent Bd-GPL strain on skin secreted chemical defences and life history traits during early ontogeny of agile frogs (Rana dalmatina) and common toads (Bufo bufo). RESULTS: Exposure to Bd during the larval stage did not result in enhanced synthesis of the antimicrobial peptide Brevinin-1 Da in R. dalmatina tadpoles or in increased production of bufadienolides in B. bufo tadpoles. However, exposure to Bd during the larval stage had a carry-over effect reaching beyond metamorphosis: both R. dalmatina and B. bufo froglets contained smaller quantities of defensive chemicals than their Bd-naïve conspecifics in the control treatment. Prevalence of Bd and infection intensities were very low in both larvae and metamorphs of R. dalmatina, while in B. bufo we observed high Bd prevalence and infection intensities, especially in metamorphs. At the same time, we did not find a significant effect of Bd-exposure on body mass or development rate in larvae or metamorphs in either species. CONCLUSIONS: The lack of detrimental effect of Bd-exposure on life history traits, even parallel with high infection intensities in the case of B. bufo individuals, is surprising and suggests high tolerance of local populations of these two species against Bd. However, the lowered quantity of defensive chemicals may compromise antimicrobial and antipredatory defences of froglets, which may ultimately contribute to population declines also in the absence of conspicuous mass-mortality events