Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTS666. Genomic footprint of adaptive divergence in Ophiostoma montium, a fungal symbiont associated with the mountain pine beetle. J. F. Mao, B.Dhillon, C. Tsui, K. Ritland, R. Hamelin. Faculty of Forest Sciences, University of British Columbia, Vancouver, BC, Canada.Ophiostoma montium is the most common fungus associated with the mountain pine beetle, the insect responsible for the destruction of 18 million haof pine forests in Canada. In order to determine the evolutionary histories of O. montium populations, high-throughput genome sequencing was used touncover the genetic changes that accompany divergence as lineages colonize different conifer hosts in different climatic regions. 36 fungal isolates fromdifferent hosts and different environments were sequenced. De novo genome assembly from one isolate was used as reference to call variants (922,000SNPs and 126,000 Indels). Multiple analyses including whole genome variants, genetic distance, population structure and Identity by descent (IBD)identified three population lineages, corresponding to the various hosts and three geographic groups: US, Rocky, and North Canada (NC). Faster linkagedisequilibria (LD) decays were observed in both Rocky and NC groups, indicating an increase in genomic recombination and/or high effective populationsize. Presence of genomic regions with high LD and negative Tajima's D was evidence that population size expansion (after bottleneck or a selectionsweep) and/or purifying selection occurred in the NC group. Loci in the genome contributing to both host shift and climatic transition were also identifiedby multiple lineage-specific genomic scans for selection. Additionally, genome recombination events were recovered for lineages experiencing differentdemographic histories. Our study highlights the value of whole genome sequences both in evolutionary dynamics and genetics of plant pathogens.667. Ecological context in symbioses: when is your enemy also your friend? Georgiana May 1 , Paul Nelson 2 . 1) Dept Ecol, Evol, Behavior,#100, UnivMinnesota, St Paul, MN; 2) EEB graduate program University of Minnesota St. Paul MN.Most plants are rife with fungal symbiotic partners with many of these having little apparent effect on the host's health and fitness. In this work, weexplore the degree to which the outcome of interactions between an endophytic fungus, pathogen and plant host depend on ecological context. Inparticular, we ask whether interactions between the endophyte of maize, Fusarium verticilliodes, with the pathogen Ustilago maydis, depend on hostresistance to the pathogen. In the case of a host susceptible to the pathogen, the two fungal species should meet frequently, and compete over hostresources, potentially driving greater virulence to the host in one or the other fungal species. In the case of a host resistant to the pathogen, theendophyte might be a "bystander" to the pathogen, because the two meet too infrequently to drive their co-evolutionary interaction. We show evidencethat the two fungal species have evolved stronger antagonistic interactions in maize susceptible to the pathogen, and further, that this might beassociated with greater virulence by the pathogen. Results of modeling will also be presented from which we predict longer term evolutionary trajectoriesfor this 3-way interaction.27th Fungal Genetics Conference | 285