Ampelomyces strains isolated from diverse powdery mildew hosts in Japan: Their phylogeny and mycoparasitic activity, including timing and quantifying mycoparasitism of Pseudoidium neolycopersici on tomato

Abstract

A total of 26 Ampelomyces strains were isolated from mycelia of six different powdery mildew species that naturally infected their host plants in Japan. These were characterized based on morphological characteristics and sequences of ribosomal DNA internal transcribed spacer (rDNA-ITS) regions and actin gene (ACT) fragments. Collected strains represented six different genotypes and were accommodated in three different clades of the genus Ampelomyces. Morphology of the strains agreed with that of other Ampelomyces strains, but none of the examined characters were associated with any groups identified in the genetic analysis. Five powdery mildew species were inoculated with eight selected Ampelomyces strains to study their mycoparasitic activity. In the inoculation experiments, all Ampelomyces strains successfully infected all tested powdery mildew species, and showed no significant differences in their mycoparasitic activity as determined by the number of Ampelomyces pycnidia developed in powdery mildew colonies. The mycoparasitic interaction between the eight selected Ampelomyces strains and the tomato powdery mildew fungus (Pseudoidium neolycopersici strain KTP-03) was studied experimentally in the laboratory using digital microscopic technologies. It was documented that the spores of the mycoparasites germinated on tomato leaves and their hyphae penetrated the hyphae of Ps. neolycopersici. Ampelomyces hyphae continued their growth internally, which initiated the atrophy of the powdery mildew conidiophores 5 days post inoculation (dpi); caused atrophy 6 dpi; and complete collapse of the parasitized conidiphores 7 dpi. Ampelomyces strains produced new intracellular pycnidia in Ps. neolycopersici conidiophores ca. 8–10 dpi, when Ps. neolycopersici hyphae were successfully destroyed by the mycoparasitic strain. Mature pycnidia released spores ca. 10–14 dpi, which became the sources of subsequent infections of the intact powdery mildew hyphae. Mature pycnidia contained each ca. 200 to 1,500 spores depending on the mycohost species and Ampelomyces strain. This is the first detailed analysis of Ampelomyces strains isolated in Japan, and the first timing and quantification of mycoparasitism of Ps. neolycopersici on tomato by phylogenetically diverse Ampelomyces strains using digital microscopic technologies. The developed model system is useful for future biocontrol and ecological studies on Ampelomyces mycoparasites.

Niche differentiation within a cryptic pathogen complex: climatic drivers and hyperparasitism at multiple spatial scales

“…When parasitized by Ampelomyces , the asexual and sexual sporulation of powdery mildew species is reduced or completely halted (Falk et al 1995, Legler et al 2016). Molecular studies revealed that Ampelomyces is a genetically diverse group of intracellular fungal hyperparasites, with four major clades (putative species) (Kiss 1998, Park et al 2010, Kiss et al 2011, Németh et al 2021). Hyperparasites can be identified by a change in colour of the powdery mildew colony from white to brown, and microscopically based on the presence of asexual fruiting bodies (pycnidia), but molecular assessment is probably the most accurate mode of detection.…”

The “Bipartite” Structure of the First Genome of Ampelomyces quisqualis, a Common Hyperparasite and Biocontrol Agent of Powdery Mildews, May Point to Its Evolutionary Origin from Plant Pathogenic Fungi

“…Some Ampelomyces strains have been commercialized as biocontrol agents of crop pathogenic powdery mildews ( Boddy 2015 ; Legler et al 2016 ). The taxonomy of the genus Ampelomyces is unresolved, but well-supported molecular operational taxonomic units (MOTUs) were defined suggesting that the genus may include at least four to seven species ( Liang et al 2007 ; Park et al 2010 ; Kiss et al 2011 ; Angeli et al 2012 ; Pintye et al 2012 ; Liyanage et al 2018 ; Németh et al 2019 ; Németh, Mizuno, et al 2021 ). All strains belonging to the genus Ampelomyces are hyperparasites of powdery mildews just like the type species A. quisqualis .…”

“…Our phylogenetic analysis presented here revealed that BRIP 72107 is not conspecific with HMLAC 05119, the only Ampelomyces strain with a known genome ( Haridas et al 2020 ). BRIP 72107 is, however, conspecific with the commercial AQ10 strain, and both belong to the MOTU that has included many Ampelomyces strains newly isolated from the field in diverse studies in China, Europe, Japan, the United States, and Korea ( Liang et al 2007 ; Park et al 2010 ; Kiss et al 2011 ; Pintye et al 2012 ; Liyanage et al 2018 ; Németh, Mizuno, et al 2021 ). Therefore, this genome will be useful to decipher molecular mechanisms underlying both biocontrol processes and natural tritrophic interactions.…”

Hyperparasitic fungi on black mildews (Meliolales, Ascomycota) : hidden diversity in the tropics

“…are easily identified by a change in color, from white to brown (Faticov et al ., 2022;Németh et al ., 2019). While molecular studies have revealed that Ampelomyces may comprise at least four to seven species, the taxonomy within the genus is unresolved (Németh et al ., 2019(Németh et al ., , 2021.…”

“…Ampelomyces quisqualis has been the subject of numerous investigations on biological control of powdery mildews for over 50 years and, along with species of Trichoderma, they are the most common biocontrol agents that have reached international markets (Falk et al ., 1995a(Falk et al ., , 1995bKiss et al ., 2004). Several crossinoculation experiments, both in vitro and in the field (Angeli et al ., 2012;Kiss et al ., 2011;Legler et al ., 2016;Liang et al ., 2007;Németh et al ., 2021), have shown that species of Ampelomyces are not strictly host specific. This has allowed for biocontrol agents composed of a single strain to be applied to a wide range of powdery mildew species (Németh et al ., 2021).…”