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Poster: Biology & Disease Mgmt: Mycology


Fusarium oxysporum f.sp. lycopersici: Small Chromosomes Define Friend vs Foe.
K. FENSTERMACHER (1) (1) Penn State University, U.S.A.

Fusarium is a genus of filamentous fungi well-known for causing persistent wilt diseases on almost all cultivated crops. The Fusarium oxysporum Species Complex has no known sexual stage, yet is diverse and contains over 120 formae speciales that cause disease on different plant hosts. In 2010, Ma et al. sequenced F. oxysporum f.sp. lycopersici (Fol) to find virulence loci of differing GC content throughout the genome, including small, conditionally dispensable chromosomes (CDCs) that do not match known Fusarium sequences, contain genes with no known homologs, can convey pathogenicity when transferred from a pathogenic strain to a non-pathogenic relative—making them functionally similar to virulence plasmids in bacteria. CDCs could explain the high level of diversity observed in a microbe with no sexual recombination, and the inconsistent number and sizes of chromosomes consistently found in these plant pathogens. This project sampled over 40 sites, with and without known cases of Fol, to examine 1) the prevalence of CDCs where Fol is found, 2) the variation among CDCs and pathogen phenotypes, and 3) the variation within genetic backgrounds harboring different CDCs. This data will help determine the roles of CDCs in the context of the populations and growing systems in which they are found, to analyze the potential of previous or future horizontal chromosome transfer events under various conditions, and analyze the risk factors and effects on agricultural systems.