Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSmating types. Additionally, by analyzing meiotic progeny of C. amylolentus, we found evidences that both MAT loci are linked to their respectivecentromeres. Using both genetics and genomics techniques, we further narrowed down the candidate centromeric regions to be located within 150 and100 kb from the A and B MAT loci, respectively. Furthermore, genome comparison between C. neoformans and C. amylolentus showed that the majority ofcentromeres in C. neoformans are flanked by sequences from different chromosomes in C. amylolentus, indicating that ectopic recombination withincentromeric regions may frequently lead to chromosomal translocations. We propose a model in which the large bipolar MAT locus that is present in thepathogenic Cryptococcus species complex originated through ectopic recombination in the centromeres (possibly mediated by common repetitivesequences present in the centromeric regions). This process brought together the two MAT loci of the ancestral tetrapolar mating system onto the samechromosome, and subsequent chromosomal rearrangements (inversions and transpositions) resulted in the current state of the MAT locus seen in thederived bipolar pathogenic Cryptococcus species.645. Evolutionary history and genetic diversity of Exobasidium sp., the cause of an emerging disease of blueberry. Marin Brewer, Ashley Turner.Department of Plant Pathology, University of Georgia, Athens, GA.Emerging fungal diseases, usually the result of pathogen introductions, the evolution of virulent races, or adaptation to new niches, are an increasingthreat. Exobasidium fruit and leaf spot of blueberry has rapidly increased in incidence in the southeastern USA over the past two years. We took aphylogenetic approach to understand the evolutionary history of this fungus. We sequenced the LSU-rDNA region from nine isolates collected from fruit orleaf spots of Vaccinium spp. from Georgia and North Carolina. Additionally, sequences from GenBank with high similarity to the emerging parasite andfrom Exobasidium spp. parasitizing other Vaccinium spp. in North America were obtained. The sequences were assembled, aligned and subjected tophylogenetic analyses. Results indicated that Exobasidium sp. from blueberry in the southeastern USA is unique and distinct from Exobasidium sp. thatcauses a leaf spot on lowbush blueberry in the northeastern USA and Canada. Both species, however, are genetically different from other Exobasidiumspp. that cause diseases on cranberry and blueberry, and from E. vaccinii from V. vitis-idaea. Results also suggested that within the Southeast the parasiteis not genetically differentiated based on blueberry host species or cultivar, host tissue (fruit or leaf), or geographic region. To further investigate diversityand population structure of the parasite in the Southeast we sequenced ITS for 80 isolates from diverse host species, cultivars, and locations. We obtained75 unique sequences, which is an extremely high level of diversity and is unexpected for any fungus let alone one causing an emerging disease. The highdiversity indicates that the fungus causing Exobasidium fruit and leaf spot in the Southeast is not an evolutionarily young species and that the recentincrease in incidence is not a result of increased aggressiveness or a recent host switch. Analyses of genetic differentiation of the ITS sequences confirmour findings with LSU-rDNA that isolates within the Southeast are not differentiated by host species or cultivar, host tissue, or geographic region,suggesting that a single population is causing this disease of blueberry across the Southeast. We hypothesize that an environmental change is responsiblefor the recent emergence of this disease.646. Microsatellite markers reveal population structure and genetic diversity in the blueberry pathogen Monilinia vaccinii-corymbosi. Kathleen MBurchhardt, Marc A Cubeta. Department of Plant Pathology, North Carolina State University, Raleigh, NC.The ascomycete Monilinia vaccinii-corymbosi (Mvc) is a widespread fungal pathogen of blueberry (Vaccinium spp.) in North America. Both asexual andsexual spore production are required within a season for the fungus to complete its life cycle. Overwintered infected fruit (mummies) produce apotheciathat release aerially dispersed ascospores which infect newly emerging blueberry shoots, resulting in blighting of infected tissues followed by productionof conidia. Insect pollinators deposit conidia on flowers that infect the ovary through the gynoecial pathway, leading to fruit mummification. The primaryobjective of our research was to use population genetics-based approaches to examine genetic diversity, structure, and gene flow among populations ofMvc throughout the United States. A total of 437 samples from 18 blueberry fields in 10 states (one field in GA, MA, ME, MI, MS, NJ, NY, OR, and WA and 9fields in NC) were analyzed with 10 microsatellite markers. Population genetic analyses supported population structure and high intraspecific geneticdiversity, with 203 unique multilocus haplotypes (MLHs) identified from the samples. However, there were differences in genetic diversity and populationstructure based on locality and host species. Low genetic diversity and selfing were suggested based on analysis of samples of infected shoots or fruitcollected from rabbiteye (V. virgatum) varieties in MS, GA, and five fields in NC. Only three unique MLHs were identified from analyzing the 141 samplescollected from the seven fields, with two of the unique MLHs detected within four and five of the fields, respectively. At least 12 unique MLHs weredetected within all other fields except OR, with all MLHs being exclusive to their field of origin. Samples from the 10 fields were collected from eitherinfected shoots of rabbiteye, northern highbush (V. corymbosum), or southern highbush (V. corymbosum x V. darrowii), or from infected fruit of northernhighbush or lowbush (V. angustifolium). Analysis of molecular variance and the software STRUCTURE supported significant genetic differentiation amongthese fields, indicating restricted gene flow. The majority of microsatellite markers were in linkage equilibrium within the fields, suggesting randommating. Future research will examine the potential for host specialization of isolates of Mvc.647. Genetic diversity of Australian Pyrenophora tritici-repentis isolates using microsatellites. Caroline Moffat, Pao Theen See, Rick Dolling, RichardOliver. Department of Environment & Agriculture, Curtin University, Perth, WA, Australia.Pyrenophora tritici-repentis, the causal agent of tan spot of wheat, is an economically significant necrotrophic fungal pathogen. In Australia, tan spot isthe most damaging wheat disease, resulting in yield losses of $212 million per annum. The disease was first recorded in Australia in the 1950s, some tenyears after it was initially reported on wheat in the USA. Here, we examine the genetic diversity of a collection of Australian P. tritici-repentis isolates usingmicrosatellites. We discuss relatedness and structure, and consider the findings in the broader context of biogeography.648. WITHDRAWN649. Fungal community composition analysis by Internal Transcribed Spacer (ITS) sequencing using Illumina MiSeq. Robin A. Ohm 1 , Julien Tremblay 1 ,Kanwar Singh 1 , Feng Chen 1 , Claude Murat 4 , Matthias Hess 1,2,3 , Francis Martin 4 , Susannah G. Tringe 1 , Igor V. Grigoriev 1 . 1) US DOE Joint Genome Institute,Walnut Creek, CA., USA; 2) Systems Biology & Applied Microbial Genomics Laboratory, Washington State University, USA; 3) Chemical and BiologicalProcess Development Group, Pacific Northwest National Laboratory; 4) Lab of Excellence ARBRE, Tree-Microbes Interactions Department, INRA, Nancy,France.Fungal species identification and community surveys relied for a long time on Internal Transcribed Spacer (ITS) sequencing using the Sanger platform.Later, 454 (Roche) pyrosequencing was used for the same purpose, capturing shorter ITS1 or ITS2 fragments, or more recently the entire ITS region usinglonger 454 XLR reads. The Illumina sequencing platform has now largely surpassed 454 in terms of read quantity and quality (e.g., HiSeq2000 yields of upto 600 Gb in a single run) but the length of produced reads (up to 150 bp in HiSeq2000) is insufficient for ITS analysis. Illumina’s newly-introduced MiSeqsequencing platform can produce paired-end 250 base reads in a single day run, which, when combined, would cover most of either ITS1 or ITS2 regions.280