0 MELLOY, P HOLLAWAY, G LUCK, J NORTON, R AITKEN, E CHAKRABORTY, S 2010 Production and fitness of Fusarium pseudograminearum inoculum at elevated carbon dioxide in FACE Global Change Biology <p>Rising atmospheric carbon dioxide (CO<span style="font-size: xx-small">2</span>) concentration is increasingly affecting food production but how plant diseases will influence production and quality of food under rising CO<span style="font-size: xx-small">2 </span>is not well understood. With increased plant biomass at high CO<span style="font-size: xx-small">2</span> the stubble-borne fungal pathogen <em>Fusarium pseudograminearum</em> causing crown rot (CR) of wheat may become more severe. We have studied inoculum production by <em>Fusarium</em> using fungal biomass per unit wheat stubble, stem browning from CR and the saprophytic fitness of <em>Fusarium </em>strains isolated from two wheat varieties grown in 2007 and 2008 at ambient and elevated CO<span style="font-size: xx-small">2</span> in free-air CO<span style="font-size: xx-small">2 </span>enrichment (FACE) with or without irrigation and once in a controlled environment. Fungal biomass, determined using primers for fungal ribosomal <em>18s</em> and the <em>TRI5 </em>gene, increased significantly at elevated CO<span style="font-size: xx-small">2</span> in two of the three studies. Stem browning increased significantly at elevated CO<span style="font-size: xx-small">2</span> in the 2007 FACE study. At elevated CO<span style="font-size: xx-small">2 </span>increased stem browning was not influenced by irrigation in a susceptible variety but in a resistant variety stem browning increased by 68% without irrigation. Wheat variety was significant in regression models explaining stem browning and <em>Fusarium</em> biomass but pathogen biomass at the two CO<span style="font-size: xx-small">2 </span>levels was not significantly linked to stem browning. <em>Fusarium</em> isolates from ambient and elevated CO<span style="font-size: xx-small">2 </span>did not differ significantly in their saprophytic fitness measured by the rate of colonization of wheat straw. We show that under elevated CO<span style="font-size: xx-small">2 </span><em>Fusarium</em> inoculum in stubbles will be amplified from increased crop and pathogen biomass while unimpeded saprophytic fitness will retain its effectiveness. If resistant varieties cannot completely stop infection, Fusarium will rapidly colonize stubble to further increase inoculum once the crop is harvested. Research should move beyond documenting the influence of elevated CO<span style="font-size: xx-small">2</span> to developing disease management strategies from improved knowledge of pathogen biology and host resistance under rising CO<span style="font-size: xx-small">2</span>.</p> <p>&nbsp;</p>