Chestnut blight is a devastating disease of Castanea spp. Mycoviruses that reduce virulence (hypovirulence) of the causative agent, Cryphonectria parasitica, can be used to manage chestnut blight. However, vegetative incompatibility (vic) barriers that restrict anastomosis-mediated virus transmission hamper hypovirulence efficacy. In order to effectively determine the vegetative incompatibility genetic structure of C. parasitica field populations, we have designed PCR primer sets that selectively amplify and distinguish alleles for each of the six known diallelic C. parasitica vic genetic loci. PCR assay results were validated using a panel of 64 European tester strains with genetically determined vic genotypes. Analysis of 116 C. parasitica isolates collected from five locations in the eastern United States revealed 39 unique vic genotypes and generally good agreement between PCR and tester strain coculturing assays in terms of vic diversity and genotyping. However, incongruences were observed for isolates from multiple locations and suggested that the coculturing assay can overestimate diversity at the six known vic loci. The availability of molecular tools for rapid and precise vic genotyping significantly improves the ability to predict and evaluate the efficacy of hypovirulence and related management strategies.

2016-11-03T14:11:40

Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but a few species keep insects alive while sporulating, which enhances dispersal. Transcriptomics- and metabolomics-based studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses. However, the mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina -infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora , which likely represent a single fungal species. The absence of some fungal enzymes necessary for cathinone and psilocybin biosynthesis along with the inability to detect intermediate metabolites or gene orthologs are consistent with possibly novel biosynthesis pathways in Massospora . The neurogenic activities of these compounds suggest the extended phenotype of Massospora that modifies cicada behavior to maximize dissemination is chemically-induced.

Brachycybe (Wood) is a genus of fungivorous millipedes. To date, the fungal associates of these millipedes have never been characterized. In an attempt to resolve these relationships, culture-based approaches combined with DNA barcode sequencing were used. Sampling of 313 individuals collected from three of four B. lecontii clades and 20 sites across seven states uncovered at least 183 genera in 40 orders from four fungal phyla. At least seven putative new species were recovered in this study, despite the use of more classical culture-based approaches. Three of these fungi were phylogenetically resolved using ITS + LSU and include two new species, aff. Fonsecaea sp., Mortierella aff. ambigua, and a new genus related to Apophysomyces. Overall, the results of this study highlight the vast amount of undescribed fungal biodiversity associated with millipedes. Twelve fungal genera from nine orders showed high connectivity across the entire B. lecontii-associated fungal network, indicating a central role for these fungi in their association with these millipedes. These twelve include the two putative new species described above. The ecology of these and other fungal associates were also explored, using fungal cohort pairings and entomopathogenicity trials. Over 40% of all fungal pairings resulted in competitive interactions, a majority of which involved inhibition or overgrowth by fungi in the Hypocreales and Polyporales, respectively. The abundance of these competitive interactions in these two orders indicate differing ecological strategies. Hypocreales used chemical warfare to competitively exclude other fungi, while Polyporales physically overgrew their competitors. Mucoromycotan fungi used a similar strategy to the Polyporales. Results of a series of entomopathogenicity trials indicated that B. lecontii was less susceptible to entomopathogenic Hypocreales than an insect model (Galleria mellonella), even though these fungi are known to attack several classes of arthropods. Furthermore, the absence of a negative interaction between B. lecontii and entomopathogenic Hypocreales may indicate a beneficial relationship. When challenged with Polyporales, B. lecontii exhibited high mortality, while G. mellonella was unaffected. This stands in sharp contrast to previous casual observations of the feeding behavior of B. lecontii. Recent discoveries of previously overlooked fungal diversity have been groundbreaking and hint at substantial cryptic fungal biodiversity across the globe. The 200-300 million-year-old association between fungi and the Colobognatha, which includes Brachycybe lecontii, provides an ideal system to uncover biodiversity and examine function of these fungi in a highly understudied and ancient association.

The Nectriaceae contains numerous canker pathogens. Due to scarcity of ascomata on many hosts, comprehensive surveys are lacking. Here we characterize the diversity of perithecia-producing nectriaceous fungi across the central Appalachians. Ten species from twelve hosts were recovered including a novel Corinectria sp. from Picea rubens.Neonectria ditissima and N. faginata were most abundant and associated with Fagus grandifolia with beech bark disease (BBD). N. ditissima was also recovered from additional cankered hardwoods, including previously unreported Acer spicatum, Ilex mucronata, and Sorbus americana. Cross-pathogenicity inoculations of N. ditissima confirmed susceptibility of Acer and Betula spp. Neonectria magnoliae was recovered from cankered Liriodendron tulipifera and Magnolia fraseri and pathogenicity on L. tulipifera was confirmed. Fusarium babinda was consistently recovered from beech with BBD, although its role remains unclear. This survey provides a contemporary snapshot of Nectriaceae diversity across the Appalachian Mountains. The following nomenclatural changes are proposed: Neonectria magnoliae comb. nov.