Structure and temporal shifts in virulence of Pseudoperonospora cubensis populations in the Czech Republic

The structure and temporal dynamics of the virulence of Pseudoperonospora cubensis (causal agent of cucurbit downy mildew) were studied in pathogen populations in the Czech Republic from 2001 to 2010. A total of 398 P. cubensis isolates collected from Cucumis (Cm.) sativus, Cm. melo, Cucurbita (Cr.) maxima, Cr. pepo, Cr. moschata and Citrullus lanatus were analysed for variation in virulence (pathotypes). Virulence was evaluated on a differential set of 12 genotypes of cucurbitaceous plants. All isolates of P. cubensis were characterized by their level of virulence (classified according the number of virulence factors, VF; low VF = 1‐4, medium VF = 5‐8, high VF = 9‐12): high (75%), medium (24%) and low (1%). The structure and dynamics of virulence in the pathogen populations were expressed by pathotypes using tetrad numerical codes and a total of 67 different pathotypes of P. cubensis were determined. The most susceptible group of differentials was Cucumis spp., while the lowest frequency of virulence was recorded on Cr. pepo ssp. pepo, Ci. lanatus and Luffa cylindrica. A high proportion (c. 90%) of isolates was able to infect cucurbit species Benincasa hispida and Lagenaria siceraria ,w hich are not commonly cultivated in the Czech Republic or elsewhere in central Europe. In the recent pathogen populations (2008‐2010) there was prevailing frequency (70‐100%) of isolates with high numbers (9‐12) of virulence factors. ‘Super pathotype’ 15.15.15 was often observed in the study within the pathogen populations and was one of the four most frequently recorded pathotypes. Pseudoperonospora cubensis populations shifted to a higher virulence over time. From 2009 the pathogen population changed dramatically and new pathotypes appeared able to establish natural and serious infection of Cucurbita spp. and Ci. lanatus, which was not observed in 2001‐2008. Generally, virulence structure and dynamics of P. cubensis populations are extremely variable in the Czech Republic.

[1]  M. Thines,et al.  The Genetic Structure of Pseudoperonospora cubensis Populations. , 2012, Plant disease.

[2]  Y. Cohen,et al.  Fungicide resistance in Pseudoperonospora cubensis, the causal pathogen of cucurbit downy mildew. , 2012 .

[3]  Y. Cohen,et al.  Mating type and sexual reproduction of Pseudoperonospora cubensis, the downy mildew agent of cucurbits , 2011, European Journal of Plant Pathology.

[4]  A. Lebeda,et al.  Distribution, Host Range and Disease Severity of Pseudoperonospora cubensis on Cucurbits in the Czech Republic , 2011 .

[5]  D. Gent,et al.  Genetic and pathogenic relatedness of Pseudoperonospora cubensis and P. humuli. , 2011, Phytopathology.

[6]  A. Lebeda,et al.  First Report of Pseudoperonospora cubensis on Cucurbita moschata in the Czech Republic. , 2011, Plant disease.

[7]  G. Holmes,et al.  Spatiotemporal spread of cucurbit downy mildew in the eastern United States. , 2011, Phytopathology.

[8]  S. Ngachan,et al.  Pseudoperonospora cubensis on Sechium edule in India , 2010, Australasian Plant Disease Notes.

[9]  Y. Cohen,et al.  Cucurbit downy mildew (Pseudoperonospora cubensis)—biology, ecology, epidemiology, host-pathogen interaction and control , 2011, European Journal of Plant Pathology.

[10]  M. Thines,et al.  Phylogenetic investigations in the genus Pseudoperonospora reveal overlooked species and cryptic diversity in the P. cubensis species cluster , 2011, European Journal of Plant Pathology.

[11]  S. Meon,et al.  Host range evaluation and morphological characterization of Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew in Malaysia , 2010 .

[12]  M. Sariah,et al.  First Report of Pseudoperonospora cubensis Causing Downy Mildew of Trichosanthes cucumerina in Malaysia. , 2010, Plant disease.

[13]  A. Lebeda,et al.  Molecular polymorphisms between populations of Pseudoperonospora cubensis from Greece and the Czech Republic and the phytopathological and phylogenetic implications , 2009 .

[14]  C. H. Lin,et al.  First Report of Downy Mildew Caused by Pseudoperonospora cubensis on Chayote (Sechium edule) in Taiwan. , 2008, Plant disease.

[15]  S. Colucci.  Host Range, Fungicide Resistance and Management of Pseudoperonospora cubensis, Causal Agent of Cucurbit Downy Mildew , 2008 .

[16]  Hyeon‐Dong Shin,et al.  First record of downy mildew caused by Pseudoperonospora cubensis on bottle gourd in Korea , 2008 .

[17]  Y. Cohen,et al.  A new pathotype ofPseudoperonospora cubensis causing downy mildew in cucurbits in Israel , 2003, Phytoparasitica.

[18]  A. Lebeda.  Screening of wildcucumis species against downy mildew (Pseudoperonospora cubensis) isolates from cucumbers , 1992, Phytoparasitica.

[19]  J. Palti.  The significance of pronounced divergences in the distribution ofpseudoperonospora cubensis on its crop hosts , 1974, Phytoparasitica.

[20]  A. Lebeda,et al.  Variation of Fungicide Resistance in Czech Populations of Pseudoperonospora cubensis , 2007 .

[21]  A. Lebeda,et al.  Temporal changes in pathogenicity and fungicide resistance in Pseudoperonospora cubensis populations. , 2007 .

[22]  A. Lebeda,et al.  Individual and population aspects of interactions between cucurbits and Pseudoperonospora cubensis: pathotypes and races , 2006 .

[23]  S. Colucci,et al.  The downy mildew epidemic of 2004 and 2005 in the eastern United States. , 2006 .

[24]  Hyeon‐Dong Shin,et al.  A re-consideration of Pseudoperonospora cubensis and P. humuli based on molecular and morphological data. , 2005, Mycological research.

[25]  E. Limpert,et al.  Analysis of diversity in populations of plant pathogens: the barley powdery mildew pathogen across Europe , 1996, European Journal of Plant Pathology.

[26]  G. Holmes,et al.  Cucurbit Downy Mildew: A Unique Pathosystem for Disease Forecasting , 2004 .

[27]  A. Lebeda,et al.  Response of Wild and Weedy Cucurbita L. to Pathotypes of Pseudoperonospora Cubensis (Berk. & Curt.) Rostov. (Cucurbit Downy Mildew) , 2004 .

[28]  A. Lebeda,et al.  Evolution and distribution of virulence in the German population of Bremia lactucae , 2003 .

[29]  A. Lebeda,et al.  A set of Cucurbitaceae taxa for differentiation of Pseudoperonospora cubensis pathotypes , 2003 .

[30]  A. Lebeda,et al.  Pathogenic variation of Pseudoperonospora cubensis in the Czech Republic and some other European countries. , 2002 .

[31]  B. McDonald,et al.  Pathogen population genetics, evolutionary potential, and durable resistance. , 2002, Annual review of phytopathology.

[32]  T. Wehner,et al.  Evidence for downy mildew races in cucumber tested in Asia, Europe, and North America , 2002 .

[33]  H. Paris,et al.  Interactions between morphotypes of Cucurbita pepo and obligate biotrophs (Pseudoperonospora cubensis, Erysiphe cichoracearum and Sphaerotheca fuliginea) , 2000 .

[34]  A. Lebeda.  PSEUDOPERONOSPORA CUBENSIS ON CUCUMIS SPP. AND CUCURBITA SPP. -RESISTANCE BREEDING ASPECTS , 1999 .

[35]  S. B. Goodwin,et al.  Population Structure of Oomycetes , 1999 .

[36]  F. J. Schwinn,et al.  The downy mildews - an overview of recent research progress. , 1994 .

[37]  A. Lebeda,et al.  Resistance of Cucurbita pepo and Cucurbita moschata varieties to cucurbit downy mildew (Pseudoperonspora cubensis) , 1993 .

[38]  A. Lebeda.  Susceptibility of accessions of Cucumis sativus to Pseudoperonospora cubensis , 1992 .

[39]  A. Lebeda.  Resistance in muskmelons to Czechoslovak isolates of Pseudoperonospora cubensis from cucumbers , 1991 .

[40]  C. Thomas,et al.  Physiological specialization in pseudoperonospora cubensis , 1987 .

[41]  A. Forsberg.  Downy mildew - Pseudoperonospora cubensis in Swedish cucumber fields in 1985. , 1986 .

[42]  S. Bains,et al.  Differential response of certain cucurbits to isolates of Pseudoperonospora cubensis and characteristics of identified races. , 1986 .

[43]  R. Tahvonen.  Downy mildew of cucurbits found for the first time in Finland. , 1985 .

[44]  Y. Cohen.  The combined effects of temperature, leaf wetness, and inoculum concentration on infection of cucumbers with Pseudoperonospora cubensis. , 1977 .

[45]  Y. Cohen,et al.  Dispersal and viability of sporangia of Pseudoperonospora cubensis. , 1971 .