Pythium oligandrum: an example of opportunistic success

Abstract

Pythium oligandrum, a non-pathogenic soil-inhabiting oomycete, colonizes the root ecosystem of many crop species. Whereas most members in the genus Pythium are plant pathogens, P. oligandrum distinguishes itself from the pathogenic species by its ability to protect plants from biotic stresses in addition to promoting plant growth. The success of P. oligandrum at controlling soilborne pathogens is partly associated with direct antagonism mediated by mycoparasitism and antimicrobial compounds. Interestingly, P. oligandrum has evolved with specific mechanisms to attack its prey even when these belong to closely related species. Of particular relevance is the question of how P. oligandrum distinguishes between self-and non-self cell wall degradation during the mycoparasitic process of pathogenic oomycete species. The ability of P. oligandrum to enter and colonize the root system before rapidly degenerating is one of the most striking features that differentiate it from all other known biocontrol fungal agents. In spite of this atypical behaviour, P. oligandrum sensitizes the plant to defend itself through the production of at least two types of microbe-associated molecular patterns, including oligandrin and cell wall protein fractions, which appear to be closely involved in the early events preceding activation of the jasmonic acid-and ethylene-dependent signalling pathways and subsequent localized and systemic induced resistance. The aim of this review is to highlight the expanding knowledge of the mechanisms by which P. oligandrum provides beneficial effects to plants and to explore the potential use of this oomycete or its metabolites as new disease management strategies.

Phylogenomic Reconstruction of the Oomycete Phylogeny Derived from 37 Genomes

“…The “peronosporalean” branches include the best-characterized oomycete taxa, Phytophthora and Pythium , and the more basal Albuginales order (1, 35). The majority of “peronosporalean” oomycetes are phytopathogens, although Pythium includes species capable of infecting animals or acting as mycoparasitic biocontrol agents (39, 40) (Fig. 1).…”

High-throughput sequencing reveals diverse oomycete communities in oligotrophic peat bog micro-habitat

“…Saprolegnia (X1602) is a wide spectrum animal parasite (Sarowar et al, 2014). Genus Pythium (X570, X716, X1311, X1846 and X2835) comprises both animal and plant parasites (Lara and Belbahri, 2011;Liu et al, 2014), fungal parasites (Benhamou et al, 2012;Horner et al, 2012) and also saprotrophic members (Kwasna et al, 2010).…”

Draft Genome Sequence of the Mycoparasitic Oomycete Pythium oligandrum Strain CBS 530.74

“…The oomycete Pythium oligandrum is an effective mycoparasite of economically important crop pathogens (1). It can directly parasitize the potato late blight pathogen Phytophthora infestans (2) and is amenable to genetic transformation (3).…”