An RNA symbiont enhances heat tolerance and secondary homothallism in the oomycete Phytophthora infestans

Despite its importance as one of the most notorious, globally distributed, multihost plant pathogens, knowledge on the survival strategy of Phytophthora cinnamomi in seasonally dry climates is limited. Soil and fine roots were collected from the rhizosphere of severely declining or recently dead specimens of 13 woody species at 11 dieback sites and two dieback spots and from healthy specimens of five woody species at four dieback-free sites in native forests, woodlands and heathlands of the south-west of Western Australia (WA). Phytophthora cinnamomi was recovered from 80.4, 78.1 and 100% of tested soil, fine root and soil-debris slurry samples at the 11 dieback sites, in some cases even after 18-month storage under air-dry conditions, but not from the small dieback spots and the healthy sites. Direct isolations from soil-debris slurry showed that P. cinnamomi colonies exclusively originated from fine roots and root fragments not from free propagules in the soil. Microscopic investigation of P. cinnamomi-infected fine and small woody roots and root fragments demonstrated in 68.8, 81.3 and 93.8% of samples from nine woody species the presence of thick-walled oospores, stromata-like hyphal aggregations and intracellular hyphae encased by lignitubers, respectively, while thin-walled putative chlamydospores were found in only 21.2% of samples from five woody species. These findings were confirmed by microscopic examination of fine roots from artificially inoculated young trees of 10 woody species. It is suggested that (i) the main function of chlamydospores is the survival in moderately dry conditions between consecutive rain events and (ii) selfed oospores, hyphal aggregations, and encased hyphae and vesicles in infected root tissue of both host and non-host species are the major long-term survival propagules of P. cinnamomi during the extremely dry summer conditions in WA.

show abstract

“…Recently, Judelson et al. () demonstrated secondary homothallism caused by an RNA symbiont in both A1 and A2 isolates of P. infestans .…”

Section: Discussionmentioning

confidence: 99%

New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia

2013

View full text Add to dashboard Cite

show abstract

“…Mating system varies extensively among oomycete plant pathogens, and even within a species depending on numerous factors (Judelson et al ., ; Han et al ., ). Mating system has been described in relatively few downy mildew organisms, although homothallism, secondary homothallism and heterothallism are known to exist (Michelmore & Ingram, , ; Inaba & Morinaka, ; Michelmore et al ., ; Sherriff & Lucas, ; van der Gaag & Frinking, ; Spring, ; Wong et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Homothallism in Pseudoperonospora humuli

2017

View full text Add to dashboard Cite

The downy mildew pathogen, Pseudoperonospora humuli, forms oospores abundantly in diseased hop tissue. Diverse monosporangial isolates of P. humuli derived from samples collected in Japan, Germany and the USA readily formed oospores within hop leaves when inoculated singly, suggesting homothallism. Single zoospore isolates also readily formed oospores within hop leaves, further supporting the homothallic nature of this oomycete. The majority of oospores were deemed viable based on cytoplasm characteristics and plasmolysis assays. However, disease symptoms failed to develop when hop leaves were inoculated with newly formed oospores, even when oospore conditioning was attempted with treatment with potassium permanganate or b-glucuronidase/arylsulphatase, brief exposure to freezing temperature, or passage through an earthworm. Oospores derived from a monosporangial isolate of P. humuli that overwintered outdoors in infested leaves buried in soil also failed to cause downy mildew. Pseudoperonospora humuli is homothallic and oospores of the organism appear to require as yet unknown conditions to stimulate their germination and/or infection.

show abstract

Phytophthora infestans

Judelson¹

2014

Genomics of Plant-Associated Fungi and Oomycetes: Dicot Pathogens

View full text Add to dashboard Cite

An RNA symbiont enhances heat tolerance and secondary homothallism in the oomycete Phytophthora infestans

Cited by 7 publications

References 56 publications

New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia

New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia

Homothallism in Pseudoperonospora humuli

Phytophthora infestans

Contact Info

Product

Resources

About