The plant response induced in wheat ears by a combined attack of Sitobion avenae aphids and Fusarium graminearum boosts fungal infection and deoxynivalenol production.

Abstract

The pathogen Fusarium graminearum, producer of the mycotoxin deoxynivalenol, and Sitobion avenae aphids both reside onwheat ears. We explored the influence of an earlier aphid infestation on the expression profile of specific molecular markers associated with F. graminearum infection. Using reverse transcription-quantitative polymerase chain reaction analysis, we followed the expression of wheat defence genes on S. avenae infestation and explored the effect on a subsequent F. graminearum infection. This was performed by the assessment of disease symptoms, fungal biomass, mycotoxin production and number of aphids at several time points during disease progress. Wheat ears infected with F. graminearum showed more disease symptoms and higher deoxynivalenol levels when ears were pre-exposed to aphids relative to a sole inoculation with F. graminearum. Aphids induced defence genes that are typically induced on F. graminearum infection. Other defence genes showed earlier and/or enhanced transcription after exposure to both aphids and F. graminearum. In the discussion, we link the symptomatic and epidemiological parameters with the transcriptional induction pattern in the plant. Our study suggests that pre-exposure of wheat ears to aphids affects the plant response, which plays a role in the subsequent attack of F. graminearum, enabling the fungus to colonize wheat ears more rapidly.