The environment has a strong influence on the abundance and distribution of plant pathogenic organisms and plays a major role in plant disease. Climatological factors may also alter the dynamics of the interactions between plant pathogens and their hosts.Nothophaeocryptopus(=Phaeocryptopus)gaeumannii, the causal agent of Swiss needle cast (SNC) of Douglas‐fir, is endemic to western North America where it exists as two sympatric, reproductively isolated lineages. The abundance of this fungus and the severity of SNC are strongly influenced by climate. We used statistical and population genetic analyses to examine relationships between environment, pathogen population structure, and SNC severity. AlthoughN. gaeumanniiLineage 2 in western Oregon and Washington was most abundant where SNC symptoms were most severe, we did not detect a significant relationship between Lineage 2 and disease severity. Warmer winter temperatures were inversely correlated with foliage retention (AFR) and positively correlated with the relative abundance of Lineage 2 (PL2). However when distance inland, which was strongly correlated with bothAFRandPL2, was included in the model, there was no significant relationship between Lineage 2 andAFR. Spring/early summer dew point temperatures also were positively associated with totalN. gaeumanniiabundance (colonization index (CI)) and inversely correlated withAFR. Warmer summer mean temperatures were associated with lowerCIand higherAFR. Our results suggest that the two lineages have overlapping environmental optima, but slightly different tolerance ranges. Lineage 2 was absent from more inland sites where winters are colder and summers are warm and dry, while Lineage 1 occurred at most sites across an environmental gradient suggesting broader environmental tolerance. These relationships suggest that climate influences the abundance and distribution of this ecologically important plant pathogen and may have played a role in the evolutionary divergence of these two cryptic fungal lineages.

Swiss needle cast (SNC) is a foliar disease of Douglas-fir (Pseudotsuga menziesii) caused by Phaeocryptopus gaeumannii (Rohde) Petrak. This fungus is endemic to western North America, where it has historically had little impact in native forests. However, increasing disease severity in western Oregon since the 1990s has prompted renewed interest in P. gaeumannii and SNC. For this study, we analyze multilocus microsatellite genotypes from 482 single-spore isolates from 68 trees across 14 sites in the western Coast Range of Oregon and southwestern Washington. This study assesses genotypic variation and genetic structure at several levels of population hierarchy. Despite the observation that most of the genetic variation occurred within subpopulations, our analyses detected significant differentiation at all hierarchical levels. Clustering among the 482 isolates based on genetic distance clearly supports the existence of two previously described cryptic lineages of P. gaeumannii in the western United States. The two lineages occur in varying proportions along latitudinal and longitudinal gradients in western Oregon and Washington, suggesting a relationship between climate and phylogeography. Sites near Tillamook, Oregon, where SNC is most severe, consist of sympatric subpopulations in which the two lineages comprise roughly equal proportions.

Agarikon (Laricifomes officinalis syn. Fomitopsis officinalis) is an endangered fungus belonging to a unique lineage in the Polyporales (Basidiomycota) with a growing body of evidence supporting its medicinal value. In this study, we report the hybrid de novo assembly and annotation of the nuclear and mitochondrial genomes of L. officinalis, with a nuclear genome size of 28.76 Mb assembled across 66 contigs (51.96% GC content; BUSCO completeness of 99.4%) and a complete core mitochondrial genome size of 197.67 kb. Structural and functional annotation of the nuclear genome yielded 8,717 predicted genes including 8,604 protein-coding genes, with 287 genes in 27 candidate biosynthetic gene clusters. We characterized the mating type loci matA and matB, consistent with a tetrapolar mating system, and identified genes encoding key enzymes involved in triterpenoid and polyketide biosynthetic pathways that lead to the production of a diverse array of secondary metabolites. Additionally, we conducted maximum likelihood phylogenomic analysis to confirm the taxonomic position of L. officinalis among other species in the Polyporales using protein sequences for 730 shared BUSCO genes. This high-quality annotated genome of L. officinalis will serve as a foundation for further investigations into its evolutionary history, provide a reference for future population genomic analyses, and elucidate mechanisms underlying the synthesis of the bioactive compounds responsible for agarikon's wide-ranging medicinal benefits.

Boiling Springs Lake (BSL) is an oligotrophic, acidic geothermal feature where even very low levels of microbial heterotrophic production still exceed

Swiss needle cast is a foliar disease of Douglas-fir (Pseudotsuga menziesii) that results in premature foliage loss and reduced growth. The causal fungus, Nothophaeocryptopus gaeumannii, was first detected in New Zealand in 1959 and spread throughout the North and South Islands over the following decades. The contemporary genetic structure of the N. gaeumannii population in New Zealand was assessed by analyzing 468 multilocus SSR genotypes (MLGs) from 2,085 N. gaeumannii isolates collected from 32 sites in the North and South Islands. Overall diversity was lower than that reported from native N. gaeumannii populations in the northwestern United States, which was expected given that N. gaeumannii is introduced in New Zealand. Linkage disequilibrium was significantly higher than expected under random mating, suggesting that population structure is clonal. Populations of N. gaeumannii in the North and South Islands were weakly differentiated, and the isolates collected from sites within the islands were moderately differentiated. This suggests that gene flow has occurred between the N. gaeumannii populations in the North and South Islands, and between the local N. gaeumannii populations within each island. Eighteen isolates of N. gaeumannii Lineage 2, which has previously been reported only from western Oregon, were recovered from two sites in the North Island and four sites in the South Island. The most likely explanation for the contemporary distribution of N. gaeumannii in New Zealand is that it was introduced on infected live seedlings through the forestry or ornamental nursery trade, as the fungus is neither seed borne nor saprobic, and the observed population structure is not consistent with a stochastic intercontinental dispersal event.