The fungal microbiome influences all aspects of plant health from growth to pathogen defense. Recent work has shown that the endophytic fungal community can experience shifts in composition as a result of pathogen infection, leading to investigations on the directionality of these compositional shifts and whether they are predictive of disease outcomes in the plant host. Here we aim to characterize and compare the fungal microbiome composition of wheat leaves under Parastagonospora nodorum infection and use P. nodorum abundance to predict disease outcomes in wheat.
Four cultivars of wheat at two sites in North Carolina were inoculated with P. nodorum, the causal agent of septoria nodorum blotch (SNB) of wheat, using infected wheat straw. Plants in wheat plots were randomly sampled for flag leaf collection, then allowed to grow until harvest, at which point scores for a variety of plant diseases were taken. ANOVA revealed that cultivar, not P. nodorum inoculation, was a significant predictor of microbiome composition (R 21= 0.24, R22=0.33, p < 0.5). Analysis of co-occurrence networks generated for the inoculated and uninoculated wheat plots suggests that P. nodorum is positively associated with multiple yeast species and negatively associated with other disease causing fungi only at sufficient abundances. Additionally, regression analysis found that P. nodorum abundance did not significantly predict the final SNB score of infected plants. We suggest that P. nodorum infection does not significantly modulate the leaf fungal microbiome in low doses, but does interact with wheat associated yeasts, whose growth may be facilitated by SNB.