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The population dynamics of coexistence between Cochliobolus sativus and Fusarium pseudograminearum in wheat
E. GUNNINK TROTH (1), J. Johnston (1), A. Dyer (1). (1) Montana State University, Bozeman, MT, U.S.A.

Both <i>Cochliobolus sativus</i> (<i>Cs) </i>and <i>Fusarium pseudograminearum</i> (<i>Fp</i>) cause substantial losses worldwide through seedling blight and crown rots of wheat. Based on reports of antagonism between the fungi, a study was conducted to examine their coexistence within wheat crowns. For this, co-inoculations of field plots were conducted at three locations using the spring wheat cultivar ‘McNeal,’ two isolates of <i>Cs,</i> and four isolates of <i>Fp</i>. Emergence, plant vigor, yield, disease severity, and pathogen populations in crown tissues as determined by quantitative polymerase chain reaction were measured. The effects the two fungi had on one another’s populations varied based on isolate. While inoculation with either <i>Cs </i>isolate significantly increased <i>Cs </i>populations in crown tissues (both <i>p<</i>0.001), only <i>Fp </i>isolate 2228 significantly reduced <i>Cs </i>populations (<i>p=</i>0.007). Conversely, all <i>Fp </i>isolates significantly increased <i>Fusarium </i>populations within crowns, while only <i>Cs </i>isolate 2344 decreased <i>Fusarium </i>populations (<i>p=</i>0.003). There was no strong correlation between populations of the two fungi (R<sup>2</sup>=0.018, <i>p=</i>0.075). For emergence, disease severity scores, and yield, the effects of inoculations were variable. Both <i>Cs </i>isolates significantly reduced emergence (both <i>p<</i>0.001), while only <i>Fp </i>isolate 2228 affected disease severity scores (<i>p=</i>0.006). Yield reductions were only associated with <i>Cs </i>populations (<i>p=</i>0.032). These dynamics provide new insight into the interactions of these pathogens.

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