Existence of different physiological forms within genetically diverse strains of Ampelomyces quisqualis

Abstract

Powdery mildew fungi are parasitized by strains of the genetically distinct Ampelomyces quisqualis. To investigate whether differences in the phylogeny and other cultural, morphological and physiological characteristics of these different strains are related to differences in their geographic origins or the host species from which they were isolated, several A. quisqualis strains isolated from different species of Erysiphaceae collected in different countries and possessing different ITS rDNA sequences were selected and characterized. The results revealed some significant variation among the selected strains, which provides evidence for the existence of different physiological forms within the A. quisqualis species. Two groups that display differential growth on artificial media were identified. These groups also differ in the morphology of their mycelium, but not in the morphology of their pycnidia and conidia. Temperature greatly affected the in vitro growth of the A. quisqualis strains and growth rate was closely correlated to colony color. Differences in the conidial germination of distinct strains were observed during the recognition phase of the parasitic relationship. The germination of each of the investigated strains was greatly stimulated by all of the examined powdery mildew species and not only by the conidia of their original hosts. An Italian strain isolated from grapevine in the Trentino Alto-Adige region was identified as the strain that germinates the most quickly in the presence of powdery mildew conidia. Phylogenetic analysis revealed that these A. quisqualis strains can be classified into five different genetic groups, which generally correlate with the fungal host of origin and morphological and growth characteristics.

Morpho-Molecular Characterization of Two Ampelomyces spp. (Pleosporales) Strains Mycoparasites of Powdery Mildew of Hevea brasiliensis

“…infecting rubber powdery mildews were hyaline, and the pycnidia and spores were pale brown in color. However, Lee et al (2007) and Angeli et al (2011) noted color variations in the mycelium and pycnidia from olive green to pale and dark brown in different mycohosts belonging to the genus Erysiphe. Pycnidia and spores were comparatively smaller in specimens of Ampelomyces isolated from rubber powdery mildews than in specimens isolated from other mycohosts in the same genus ( Angeli et al, 2011 ).…”

“…were fast growing and Ampelomyces spp. were slow-growing ( Kiss, 1998 ; Kiss and Nakasone, 1998 ; Angeli et al, 2011 ). However, Kiss (1998) pointed out that these two taxa were not closely related and possibly not congeneric.…”

“…Thus, for successful germination, the spores need both favorable conditions (high humidity or moisture and temperatures of 25°C) and the presence of the appropriate host. Without the host, viability is lost within a few days ( Mhaskar and Rao, 1974 ; Szentiványi and Kiss, 2003 ; Kiss, 2008 ; Angeli et al, 2011 ). However, Jarvis and Slingsby (1997) , and Angeli et al (2011) pointed out that A. quisqualis can survive and infective to powdery mildews even at temperatures below 12°C.…”

Local adaptation at higher trophic levels: contrasting hyperparasite–pathogen infection dynamics in the field and laboratory

“…, ; Angeli et al . ). This evidence suggests that some degree of host association and co‐evolution may occur within Ampelomyces, although strict host‐species fidelity has not evolved.…”

The possibilities of biologically protecting plants against diseases in nurseries, with special consideration of Oomycetes and Fusarium fungi

“…Small effectiveness of biological control observed in some field experiments may also stem from the use of the antagonistic organisms with narrow mechanism of impact on pathogens; therefore, it is recommended to use the microorganisms with wide range of antagonistic capacities (Cook 1993). Specialised mechanism of impact on pathogenic microorganisms is associated with very small probability of the host change, as for example, hyperparasite species of Ampelomces quisqalis -parasitising only the fungi responsible for powdery mildew (Angeli et al, 2012). According to some researchers, high host specialisation can be correlated with evolutionary liability (Parker and Gilbert 2004), while in the opinion of Heydari and Pessarakli (2010), hyperparasiting organisms introduced into the environment do not provide sufficient protection, since they exhibit an aggressive behaviour towards other organisms only under conditions of limited availability of nutrients.…”