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Determinants of aggressiveness in Fusarium graminearum.

Melissa Salazar: University of Illinois at Urbana-Champaign

<div><em>Fusarium graminearum</em>, the causal agent of Fusarium head blight (FHB) of wheat, is a devastating pathogen that causes yield and quality losses to its host. Other than deoxynivalenol (DON), little is known about pathogenesis compounds used by <em>F. graminearum</em> to infect wheat. To identify essential fungal pathogenesis genes and determine whether host resistance selects for the isolate aggressiveness, a paired strategy of isolate and transcriptome characterization of naturally infected wheat lines was implemented. A total of 197 <em>F. graminearum</em> infected samples were collected in 2016 from research sites at five Illinois locations using University of Illinois soft red winter wheat improvement program plots. Wheat lines used as a source of samples included an FHB resistant line, a moderately resistant line, a moderately susceptible line, and two highly susceptible lines. RNA extraction of twelve selected samples yielded high-quality RNA. The results of differential fungal gene expression between moderately resistant, moderately susceptible, and highly susceptible interactions will be presented. To determine functional pathogen aggressiveness, pathogen strains isolated from the same samples used for RNAseq were used to inoculate wheat cultivars with varying levels of resistance in field and greenhouse experiments. Statistical analysis is currently underway for both field and greenhouse aggressiveness assays. Preliminary data analysis suggests the existence of two types of isolates. The first group was composed of isolates that had low levels of aggressiveness on both susceptible and resistant wheat lines. The second group was composed of isolates that were significantly more aggressive on a susceptible wheat line but not aggressive on a resistant wheat line.</div>