CONICET | Buscador de Institutos y Recursos Humanos

Wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT), initially restrictedto South America, is a global threat for wheat after spreading to Asia in 2016by the introduction of contaminated seeds, raising the question about transmission ofthe pathogen from seeds to seedlings, a process so far not well understood. We thereforestudied the relationship between seed infection and disease symptoms on seedlingsand adult plants. To accomplish this objective, we inoculated spikes of wheat cv.Apogee with a transgenic isolate (MoT-DsRed,with the addition of being resistantto hygromycin). We identified MoT-DsRedin experiments using hygromycin resistancefor selection or by observation of DsRed fluorescence. The seeds from infectedplants looked either apparently healthy or shrivelled. To evaluate the transmission,two experimental designs were chosen (blotter test and greenhouse) and MoT-DsRedwas recovered from both. This revealed that MoT is able to colonize wheat seedlingsfrom infected seeds under the ground. The favourable conditions of temperature andhumidity allowed a high recovery rate of MoT from wheat shoots when grown in artificialmedia. Around 42 days after germination of infected seeds, MoT-DsRedcouldnot be reisolated, indicating that fungal progression, at this time point, did not proceedsystemically/endophytically. We hypothesize that spike infection might occurvia spore dispersal from infected leaves rather than within the plant. Because MoT-DsRedwas not only successfully reisolated from seed coats and germinating seedswith symptoms, but also from apparently healthy seeds, urgent attention is needed tominimize the risks of inadvertent dispersal of inoculum.

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