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Which morphological characteristics are most influenced by the host matrix in downy mildews? : A case study in Pseudoperonospora cubensis

By Fabian Runge, Beninweck Ndambi and Marco Thines

Abstract

Before the advent of molecular phylogenetics, species concepts in the downy mildews, an economically important group of obligate biotrophic oomycete pathogens, have mostly been based upon host range and morphology. While molecular phylogenetic studies have confirmed a narrow host range for many downy mildew species, others, like Pseudoperonospora cubensis affect even different genera. Although often morphological differences were found for new, phylogenetically distinct species, uncertainty prevails regarding their host ranges, especially regarding related plants that have been reported as downy mildew hosts, but were not included in the phylogenetic studies. In these cases, the basis for deciding if the divergence in some morphological characters can be deemed sufficient for designation as separate species is uncertain, as observed morphological divergence could be due to different host matrices colonised. The broad host range of P. cubensis (ca. 60 host species) renders this pathogen an ideal model organism for the investigation of morphological variations in relation to the host matrix and to evaluate which characteristics are best indicators for conspecificity or distinctiveness. On the basis of twelve morphological characterisitcs and a set of twelve cucurbits from five different Cucurbitaceae tribes, including the two species, Cyclanthera pedata and Thladiantha dubia, hitherto not reported as hosts of P. cubensis, a significant influence of the host matrix on pathogen morphology was found. Given the high intraspecific variation of some characteristics, also their plasticity has to be taken into account. The implications for morphological species determination and the confidence limits of morphological characteristics are discussed. For species delimitations in Pseudoperonospora it is shown that the ratio of the height of the first ramification to the sporangiophore length, ratio of the longer to the shorter ultimate branchlet, and especially the length and width of sporangia, as well as, with some reservations, their ratio, are the most suitable characteristics for species delimitation

Topics: ddc:580
Year: 2012
OAI identifier: oai:publikationen.ub.uni-frankfurt.de:27477

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  1. (2012). (1892) Description of Two New Species of Peronospora.
  2. (2007). A multi-locus chloroplast phylogeny for the Cucurbitaceae and its implications for character evolution and classifcation.
  3. (1906). A new disease of hop-vine caused by Peronoplasmopara humuli n.
  4. (2007). A new downy-mildew of the Rosaceae: Peronospora oblatispora sp.
  5. (2009). A new species of Albugo parasitic to Arabidopsis thaliana reveals new evolutionary patterns in white blister rusts (Albuginaceae).
  6. (2009). A potential perennial host for Pseudoperonospora cubensis in temperate regions.
  7. (2005). A re-consideration of Pseudoperonospora cubensis and P. humuli based on molecular and morphological data.
  8. (2003). A set of Cucurbitaceae taxa for differentiation of Pseudoperonospora cubensis pathotypes.
  9. (2009). An Introduction to the White Blister Rusts
  10. (1923). Beitra ¨ge zu einer Monographie der Gattung Peronospora Corda. Beitr Kryptog Flora Schweiz
  11. (1972). Biologie et Epidemiologie du mildiou du tournesol.
  12. (2009). Characterization of a Plasmopara species on Ambrosia artemisiifolia, and notes on P. halstedii, based on morphology and multiple gene phylogenies.
  13. (2011). Cucurbit downy mildew (Pseudoperonospora cubensis)– biology, ecology, host-pathogen interaction and control.
  14. (2007). Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.),
  15. (1931). Descriptive catalogue of the Formosan Fungi.
  16. (1989). Erstmaliger Nachweis von Oosporen von Pseudoperonospora cubensis (Berk. et Curt.) Rost. an Gewa ¨chshausgurken in O ¨ sterreich.
  17. (2011). Evidence for high degrees of specialisation, evolutionary diversity, and morphological distinctiveness in the genus Bremia.
  18. (2008). Evidence for uncharted biodiversity in the Albugo candida complex, with the description of a new species.
  19. (2010). Evolution of diversity in Albugo is driven by high host specificity and multiple speciation events on closely related Brassicaceae.
  20. (2010). Evolutionary history and diversity of white blister rusts.
  21. (2008). First record of downy mildew caused by Pseudoperonospora cubensis on bottle gourd in Korea.
  22. (2008). First report of downy mildew caused by Pseudoperonospora cubensis on Chayote (Sechium edule)i n Taiwan.
  23. (2011). Formation and infectivity of oospores of Pseudoperonospora cubensis, the causal agent of downy mildew in cucurbits.
  24. (2009). Garcı ´a-Bla ´zquez G, Oberwinkler F
  25. (1977). Growth and differentiation of sporangia and sporangiophores of Pseudoperonospora cubensis on cucumber cotyledons under various combinations of light and temperature.
  26. (2011). Host matrix has major impact on the morphology of Pseudoperonospora cubensis.
  27. (2010). Host range evaluation and morphological characterization of Pseudoperonospora cubensis, the causal agent of cucurbit downy mildew in Malaysia.
  28. (2007). How do obligate parasites evolve? A multi-gene phylogenetic analysis of downy mildews.
  29. (2009). Identity of the downy mildew pathogens of basil, coleus, and sage with implications for quarantine measures.
  30. (2008). Morphological and molecular analyses support the existence of host-specific Peronospora species infecting Chenopodium.
  31. (2007). Morphological and molecular discrimination among Albugo candida materials infecting Capsella bursa-pastoris world-wide.
  32. (2009). Morphologische und molekularbiologische Untersuchungen zum Wirtsspektrum von Pseudoperonospora cubensis und Pseudoperonospora humuli. Diploma thesis (in German),
  33. (2011). Morphology and phylogeny of Hyaloperonospora erophilae and H. praecox sp. nov., two downy mildew species co-occurring on Draba verna sensu lato.
  34. (1947). On a test of whether one of two random variables is stochastically larger than the other.
  35. (2009). Pathogenic and morphological variability of Plasmopara halstedii, the causal agent of downy mildew in sunflower.
  36. (2010). Phylogenetic investigations in the downy mildew genus Bremia reveal several distinct lineages and a species with a presumably exceptional wide host range.
  37. (2011). Phylogenetic investigations in the genus Pseudoperonospora reveal overlooked species and cryptic diversity in the P. cubensis species cluster.
  38. (2011). Phylogenetic relationships in the order Cucurbitales and a new classification of the gourd family (Cucurbitaceae).
  39. (2008). Phylogeny of Peronospora, parasitic on Fabaceae, based on ITS sequences.
  40. (2008). Progress and challenges in systematics of downy mildews and white blister rusts: New insights from genes and morphology.
  41. (1999). Pseudoperonospora cubensis on Cucumis spp. and Cucurbita spp. – resistance breeding aspects.
  42. (1975). Pseudoperonospora cubensis.
  43. (2012). Re-Evaluation of host specificity of the closely related species Pseudoperonospora humuli
  44. (2011). Recent outbreaks of downy mildew on grape ivy (Parthenocissus tricuspidata, Vitaceae) in Germany are caused by a new species of Plasmopara.
  45. (2011). Reclassification of two Peronospora species parasitic on Draba in Hyaloperonospora based on morphological molecular and phylogenetic data.
  46. (1978). Relationship between mineral nutrition of muskmelon and development of downy mildew caused by Pseudoperonospora cubensis.
  47. (1991). Resistance in muskmelons to Czechoslovak isolates of Pseudoperonospora cubensis from cucumbers.
  48. (2004). Response of wild and weedy Cucurbita L. to pathotypes of Pseudoperonospora
  49. (1992). Screening of wild Cucumis species against downy mildew (Pseudoperonospora cubensis) isolates from cucumbers.
  50. (1953). Specialization in Pseudoperonospora cubensis
  51. (1942). Specialization in Pseudoperonospora cubensis (Berk. et Curt.) Rostov. II. Comparative studies of the morphologies of the fungi from Cucumis sativus L. and Cucurbita moschata Duchesne.
  52. (2009). Taxonomy and phylogeny of the downy mildews (Peronosporaceae). In:
  53. (1959). Taxonomy of Peronospora species on Cruciferae and Chenopodiaceae.
  54. (1977). The combined effects of temperature, leaf wetness, and inoculum concentration on infection of cucumbers with Pseudoperonospora cubensis.
  55. (2009). The host range of Albugo candida extends from Brassicaceae over Cleomaceae to Capparaceae.
  56. (2011). The inclusion of downy mildews in a multi-locus-dataset and its reanalysis reveals high degree of paraphyly in Phytophthora.
  57. (1940). The infection capabilities of hop downy mildew.
  58. (1904). The proof and measurement of association between two things.
  59. (1981). The Taxonomy of Pseudoperonospora.
  60. (2007). The variability of Peronospora alta Fuckel conidia in dependence on the ecological conditions. In:
  61. (2009). Two novel Peronospora species are associated with recent reports of downy mildew on sages.
  62. (1918). U ¨ber die Formen der Peronospora parasitica (Pers.) Fries.

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