Multiple barcode assessment within the Saprolegnia-Achlya clade (Saprolegniales, Oomycota, Straminipila) brings order in a neglected group of pathogens

Abstract

The Saprolegnia-Achlya clade comprises species of major environmental and economic importance due to their negative impact on aquaculture and aquatic ecosystems by threatening fishes, amphibians, and crustaceans. However, their taxonomy and phylogenetic relationships remain unresolved and suffer from many inconsistencies, which is a major obstacle to the widespread application of molecular barcoding to identify pathogenic strains with quarantine implications. We assessed phylogenetic relationships of major genera using three commonly used markers (ITS, SSU rRNA, and LSU rRNA). A consensus tree of the three genes provided support for nine clades encompassing eleven documented genera and a new clade (SAP1) that has not been described morphologically. In the course of this study, we isolated a new species, Newbya dichotoma sp. nov., which provided the only culture available for this genus. In parallel, we attempted to summarize the evolution of traits in the different genera, but their successive reversals rendered the inference of ancestral states impossible. This highlights even more the importance of a bar-coding strategy for saprolegniacean parasite detection and monitoring.

A fluorescence‐based assay for in vitro screening of Saprolegnia inhibitors

“…Saprolegnia is an oomycete which traditionally was classified as fungi, but due to its unique nature, it has been relocated within Straminipila (Steciow et al . ). Therefore, cell viability protocols for fungi usually do not work with Saprolegnia without adaptation.…”

“…We found that the viability of all selected strains could be determined using FUN-1 dye and no variations were observed among tested species. Saprolegnia is an oomycete which traditionally was classified as fungi, but due to its unique nature, it has been relocated within Straminipila (Steciow et al 2014). Therefore, cell viability protocols for fungi usually do not work with Saprolegnia without adaptation.…”

Taxonomical and functional diversity ofSaprolegnialesin Anzali lagoon, Iran

“…Understandably, integration of mycological approaches into aquatic ecology is difficult, with vague morphological features contributing to the inability to distinguish between species in situ . This is particularly true for Saprolegniales taxa for which species identification is complex and often lacks a conclusive and consistent morphological form (Hulvey et al 2007; Steciow et al 2014). With this study, by assessing the number of isolated colonies we were able to better assess the occurrence and distribution of these organisms in the environment.…”

“…Also, lack of type species and accurate description make it even harder to define specific species (Sandoval-Sierra et al 2015, 2014). Recently, sequencing of the ribosomal internal transcribed spacer (ITS) has been applied to create a phylogenetic framework within which to address issues of morphological and taxonomic ambiguity (Steciow et al 2014). Whether complementary molecular targets, in addition to the de facto ITS region, would improve this approach or are even necessary is still open to debate (Robideau et al 2011).…”

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

“…Most of the species described have been classified within two informal groups, the peronosporalean and the saprolegnialean 'galaxies' (Fuller and Jarowski, 1987). DNA based environmental surveys have shown that many more taxa, occupy basal positions within the oomycete tree (Lara and Belbahri, 2011;Steciow et al, 2013Steciow et al, , 2014. The function of some of these organisms (obligate or facultative parasites; or strictly saprotrophic) has not been elucidated to date, and it is likely that they represent a novel diversity.…”