Phytopythium is a recently established genus with sporangial morphology similar to Phytophthora and zoospore discharge similar to Pythium. It contains 27 officially recognized species including plant pathogens as well as aquatic saprophytes. Among the most widely distributed are P. helicoides and P. vexans, followed by P. oedochilum and P. litorale, each having been reported on six continents. This study uses morphological and molecular analyses to describe two novel Phytopythium species: P. phamii from river water in Vietnam and P. virginianum from an irrigation pond in the USA and citrus orchard soil in Vietnam. Based on the maximum likelihood and Bayesian phylogenies, P. virginianum and P. phamii generally grouped with members of the Phytopythium clade 2, near P. chamaehyphon and P. helicoides. Isolates of both species grew at temperatures between 7 and 35 C, with an optimum temperature of 30 C for P. phamii and 35 C for P. virginianum. Although abundant oospore production was observed in cultures of P. phamii, none was observed in cultures of P. virginianum on any of the media used. The formal description of these new species helps scientists and regulators understand the geographic distributions of organisms and identify potential emerging pathogens that can become a threat to agricultural crops.
The new genus Marsonomyces is proposed to accommodate two new species, M. pinicola and M. salicacearum, collected between 1990 and 2020 at four locations in Europe (Germany, the Netherlands, Poland) and Macaronesia (Tenerife). The most striking characteristics of the genus are large, long-cylindrical, ~128-spored asci with inamyloid, thin-walled, hemispherical apices and minute, allantoid ascospores aggregating prior to discharge in a large, elongated spore cluster. The observed polyspory is a result of seven nuclear divisions prior to spore wall formation. Phylogenetic rDNA and multigene analyses suggest placement in the family Cenangiaceae, in sister position to a clade comprising Encoelia/Velutarina, Cenangiopsis, and Trochila. This relationship is supported by morphological traits, such as brown, coriaceous, drought-tolerant apothecia growing on xeric branches, erumpent from bark (but also superficially on wood), the presence of refractive vacuolar bodies in the living paraphyses, the absence of an ionomidotic reaction, and allantoid ascospores. The two new species are morphologically very similar but can be distinguished by wider spores, the presence of hairs and occurrence on gymnosperms in M. pinicola, and the presence of rhomboid crystals and occurrence on angiosperms in M. salicacearum. Marsonomyces represents the first known case of true polyspory within the Helotiales. A possible parasitism on perithecia and pycnidia of unidentified Diaporthales is discussed. Another fungicolous member of Cenangiaceae, Hymenobolus kmetii, was investigated. Morphological reexamination of the holotype confirmed its conspecificity with Mycosphaerangium quercinum. The phylogenetically closely related genera Mycosphaerangium and Neomelanconium share numerous morphological characteristics. Consequently, Mycosphaerangium is synonymized with the older Neomelanconium, and the new combinations N. kmetii, N. magnisporum, and N. tetrasporum are proposed.
Recent advances in fungal genome sequencing have dramatically altered our understanding of the phylogeny and evolution of Fungi. However, there are still many poorly studied obligate parasitic or symbiotic fungi for which we lack any genomic information or knowledge of where they fit in the fungal phylogeny. Ancylistes, an endoparasite of desmid green algae, is such an understudied fungal genus that is classified among Entomophthoromycotina in Zoopagomycota on the basis of morphology. However, this relationship is perplexing, because Zoopagomycota is almost entirely composed of animal-associated fungi. In this study, we found and cultivated Ancylistes closterii with its green algal host Closterium sp. and sequenced its genome to investigate its phylogenetic position and evolution. Phylogenetic analyses using rDNA and genome-scale data sets showed that A. closterii was sister to other Entomophthoromycotina fungi, confirming the taxonomic position of Ancylistes. Despite the ecological distinctiveness between Ancylistes and other Entomophthoromycotina fungi, our comparative genomic analyses revealed shared traits of these fungi such as lineage-specific subtilases and hybrid histidine kinases. Ancylistes also possessed unique genes among Zoopagomycota fungi such as plant cell wall-degrading enzymes that could be important for infection of algae.
Fungi in Alternaria sections Infectoriae and Pseudoalternaria are commonly associated with commercially important crops, yet their biosystematics remains difficult to resolve because standard molecular markers often lack sufficient phylogenetic resolution. In this study, we used candidate loci identified in previous phylogenomic analyses to develop four new molecular markers (SIP-03, SIP-04, SIP-06, and SIP-08) that were specifically designed to be highly informative for these two sections. The performance of these new markers was evaluated using 237 strains collected primarily from wheat in Canada and tomatoes in the Baltic states, representing the largest data set analyzed to date. The four markers showed high amplification success and contained strong phylogenetic signal. Combined phylogenetic analyses recovered all of the previously recognized lineages within sections Infectoriae (Inf1, Inf3, Inf3) and Pseudoalternaria (Pse1, Pse2) and revealed a novel lineage, designated Inf4, associated with wheat in western Canada. Concordance of lineage assignment was high, with 94.1% of strains being placed consistently across all four markers and an overall marker conflict frequency of less than 3%. Our expanded sampling identified some lineage-specific patterns in regard to host association and geographic distribution. For example, the Inf1 lineage showed high molecular diversity and was dominant among tomato-associated strains from Baltic Europe, whereas Inf2 and Pse2 were the primary lineages infecting western Canadian wheat. Our study provides robust new tools for identification and classification of taxa within sections Infectoriae and Pseudoalternaria, refines their phylogenetic framework, and facilitates future studies on the pathology, epidemiology, and mycotoxin production of these agriculturally important fungi.
