The hemibiotrophic fungus Zymoseptoria tritici is the causative agent of Septoria tritici leaf blotch (STB) disease of wheat (Triticum aestivum L.), the economically most damaging disease of wheat in Europe. Today, ecofriendly plant protection methods compatible with sustainable agriculture are strongly desirable. Here, we tested two chemical inducers β-aminobutyric acid (BABA) and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) and the two biotic inducers Pseudomonas protegens CHA0 (CHA0) and P. chlororaphis PCL1391 (PCL) for their ability to induce resistance against STB in wheat seedlings. At 21 days after inoculation, only plants treated with BABA showed a smaller area covered by lesions and less pycnidia compared to the untreated control plants. We evaluated spore germination and fungal development on inoculated wheat leaves at early infection stages using calcofluor white staining. Overall, spores of Z. tritici germinated less on plants soil-drenched with BABA and BTH and their hyphal growth was significantly delayed. On the contrary, CHA0 and PCL seed treatments did not affect fungal growth in wheat leaves. In conclusion, BABA efficiently enhanced plant resistance to Z. tritici, BTH delayed fungal development at early stages while the two biotic inducers did not influence the resistance against STB disease.
