Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSof chemotypes in F. graminearum. Our study also suggests that F. graminearum seems to be significantly insensitive to respiratory complex inhibitors (IIand III). Molecular mechanisms involved in the insensitivity are under investigation.672. Evolution of races within f.sp lycopersici of Fusarium oxysporum. BV. Chellappan, PM. Houterman, M. Rep, BJC. Cornelissen. Molecular PlantPathology, University of Amsterdam, SILS, Science Park 904, 1090 GE Amsterdam, The Netherlands.Three physiological races (1, 2 and 3) of Fusarium oxysporum f.sp lycopersici (Fol) have been identified based on their inability to infect tomato cultivarscarrying Fol resistance genes (I, I-2 or I-3, respectively). We wished to unravel the molecular mechanisms underlying the evolution of Fol races. It isgenerally assumed that race 2 evolved from race 1 by loss of AVR1 and that race 3 evolved from race 2 by a point mutation in AVR2, thus overcoming I andI-2 mediated resistance, respectively. We have sequenced a genomic region of approximately 100 kb containing AVR1 in race 1 isolate Fol004 andcompared it to the sequenced genome of race 2 isolate Fol4287. A genomic fragment of 30.5 kb containing AVR1 was found to be missing in Fol4287.Further analysis suggests that race 2 evolved from race 1 by deletion of this 30.5 kb fragment, most likely due to recombination between helitronsbordering the fragment. A worldwide collection of Fol isolates was subjected to PCR analysis of the AVR1 genomic region, including the two borderinghelitrons. The results suggest that, based on the deletion event that led to loss of AVR1, Fol isolates can be divided into distinct lineages that coincide withtheir geographical origin. Our results also suggest that transposable elements played a major role in the evolution of races within f.sp lycopersici ofFusarium oxysporum.673. Detection of Mitochondrial DNA Heteroplasmy in the progeny of crossed genetically divergent isolates of Arbuscular Mycorrhizal Fungi. MaryamNadimi, Ivan de la Providencia, Gabriela Rodriguez, Denis Beaudet, Moahmed Hijri. IRBV, Biological Sciences Dep., University of Montreal, Montreal, QC,Canada.Nonself fusion and nuclear genetic exchange has been documented in arbuscular mycorrhizal fungi (AMF) particularly in Glomus irregulare, which is acommon and widespread species. However, mitochondrial transmission accompanying nonself fusion of genetically divergent isolates remains unknown.We developed a series of crossing experiments between different isolates of G. irregulare, harboring genetically divergent mitochondrial DNA (mtDNA)haplotypes. We tested the hypothesis that heteroplasmy (i.e. mixture of genetically different mtDNA in a common cytoplasm) occurs in the progenies ofthe crossed isolates. Three isolates of geographically distant locations were used to investigate nonself fusions and mtDNA transmission in the progeny. Tobe able to trace the mtDNA haplotypes, we sequenced two mtDNAs of two G. irregulare isolates (DAOM-240415 and DAOM-234328) additional to thecurrent available isolate DAOM-197198. We developed isolate-specific markers in variable regions of intergenic mtDNAs (cox3-rnl) of these isolates. Threecrossing combinations in pre-symbiotic and symbiotic phases were performed. Interestingly, nonself fusion frequency was low and was usually associatedwith irregular shape and aborted spores, although normal spores were also observed. Ten progeny spores per crossing combination were genotyped usingisolate-specific markers. We showed the evidence that nonself fusion occurs between isolates originated from different continents both in pre-symbioticand symbiotic phases. Genotyping patterns of individual spores from the progenies clearly showed the presence of markers of the two parental mtDNAhaplotypes. Our results demonstrated the occurrence of mtDNA heteroplasmy in the progeny of crossed isolates. This raises the questions whethermtDNA heteroplasmy is transient or persistent in AMF? What are their consequences in evolution of AMF? Are there any conflicts of the presence ofmtDNA heteroplasmy within an individual? Further studies on vegetative compatibility and incompatibility and putative sex machinery in AMF will providenew information to explore and solve these questions and thereby advance our understanding of the evolution of AMF.674. Evolution of mode of infection in the rice blast fungus and allied species. Ning Zhang 1 , Shuang Zhao 1 , Jing Luo 1 , Guohong Cai 1 , DebashishBhattacharya 2 , Bradley Hillman 1 . 1) Plant Biology and Pathology, Rutgers Univ, New Brunswick, NJ; 2) Ecology, Evolution and Natural Resources, RutgersUniv, New Brunswick, NJ.The family Magnaporthaceae contains devastating fungal cereal and grass pathogens, such as Pyricularia oryzae (Magnaporthe oryzae, rice blast fungus),Magnaporthiopsis poae (Magnaporthe poae, summer patch pathogen of turf grasses), and Gaeumannomyces graminis (take-all fungus of various cerealsand grasses), which are popular model organisms in fungal biology and host-pathogen interaction studies. Despite their ecological and economicimportance, the phylogenetic relationships among the constituent species remain ambiguous due to the lack of convincing morphological characters andpaucity of molecular data for the majority of the non-model species in the family. In this study, our multilocus phylogeny suggests that both Magnaportheand Gaeumannomyces are polyphyletic genera. Therefore, a new genus, Magnaporthiopsis is proposed based on phylogeny and morphology. Thephylogeny also provides insights into fungal biology and pathogenesis. Pyricularia oryzae formed a basal clade, while Magnaporthiopsis poae andMagnaporthiopsis rhizophila formed another well-supported clade with Magnaporthiopsis incrustans (G. incrustans), G. graminis and Nakataea sigmoidea(Magnaporthe salvinii). The basal species infects both root and aerial parts of plant host, while the aerial infection capacity seems to be lost in the taxa ofthe latter clade. The study indicates that anamorphic and ecological features are more informative than the teleomorphic characters in definingmonophyletic groups among these taxa. In addition, we performed genome sequencing for 6 species in Magnaporthaceae: Magnaporthiopsis rhizophila,Magnaporthiopsis incrustans, Harpophora maydis, Nakataea sigmoidea, Ophioceras dolichostomum, and Pseudohalonectria lignicola, in order to conductphylogenomic and comparative genome analyses for both pathogenic and non-pathogenic members of this family.675. WITHDRAWN676. Population genomic analysis reveals a complex evolutionary history of Neurospora tetrasperma. Padraic Corcoran 1 , Fen Chen 2 , Martin Lascoux 1 ,Peixiang Ni 2 , Hanna Johanesson 1 . 1) Uppsala University, Uppsala, Sweden; 2) BGI, Hong Kong, Hong Kong.Fungal population genomics as a field of inquiry has seen a rapid growth in the recent years, with ability to sequence the genomes of multiple strains offungi sampled from many populations. These studies have aimed at utilizing a population genomic approach to understanding the evolutionary forces thathave had the greatest effect in shaping the genomes of fungal species. In this study, we extend the use of population genomics to help understand theevolutionary history of Neurospora tetrasperma. Neurospora tetrasperma has been the focus of much research in recent years, with most effort devotedto the study of its predominantly non-recombining mating type chromosomes. Here we present results of analysis on the whole genome resequencing of86 homokaryotic strains of N. tetrasperma, sampled from locations in England, New Zealand and Louisiana, USA, together with one strain each of the closeheterothallic species N. hispaniola and N. sitophila. These genomes were sequenced to a mean depth of between 25 to 30X coverage. Phylogenetic andpopulation structure analysis of the genomewide SNP data produced identified that the sequenced strains of N. tetrasperma belong to 5 previouslyrecognised lineages of N. tetrasperma. Comparisons of the multiple N. tetrasperma genomes with the N. sitophila, N. hispaniola and N. crassa genomesconfirmed previous observations on introgression, but also revealed signatures of introgression between the English population of N. tetrasperma and N.hispaniola. Furthermore, comparisons between the genomes of the two homokaryons isolated from each heterokaryon revealed a large number of27th Fungal Genetics Conference | 287