Effects of enniatin B as emerging mycotoxin and its association with deoxynivalenol on wheat microbiota

Agricultural products are commonly contaminated by Fusarium mycotoxins, including the emerging enniatin B (ENB), which has shown a consistent increase in occurrence. This mycotoxin is frequently co-detected with deoxynivalenol (DON) in wheat crops, posing an important risk for animal and human health [1]. This work aims to investigate the role of ENB in association with DON on (i) selected biocontrol agents (BCAs) and on (ii) the composition of wheat microbiota, which is considered a key factor in plant health and resilience. In this context, the growth of selected BCAs was not affected by exposure to ENB (50 µg/ml) and DON (88 µg/ml) in vitro assay. ENB treatment resulted in minor variations in the metabolomic profile of the most promising strain BCA2, which preserved its ability to inhibit DON biosynthesis in Fusarium graminearum TRI5::GFP mutant in vitro. On the other hand, the presence of F. avenaceum, as the main producer of enniatins, may interfere with the efficacy of our BCAs in field conditions. Furthermore, PacBio full-length 16S sequencing was employed to analyse possible changes in the composition of microbial communities in wheat spikes after mycotoxin exposure. The experiments were carried out using both mycotoxin-producing fungi and direct injection of mycotoxins into the spikelets. According to the results, the composition, richness and relative abundance in taxa of wheat microbiota were not significantly influenced by ENB and DON compared to the control. However, the microbial community seems to differ among samples, probably depending on the physiological characteristics of each spike. In conclusion, the ENB-DON combination appears to have minor and non-significant effects on the wheat microbiota, however F. avenaceum, including its secondary metabolites, may play an important role in modulating biocontrol mechanisms of BCAs. For this reason, it would be interesting to further investigate the role of other enniatins besides ENB. References: Key message The combination of enniatin B and deoxynivalenol has minimal impact on wheat microbiota, but F. avenaceum secondary metabolites likely drive the performance of applied biocontrol strains, so exploring the role of other enniatins is warranted. [1] Valenti, I., Tini, F., Sevarika, M., Agazzi, A., Beccari, G., Bellezza, I., Ederli, L., Grottelli, S., Pasquali, M., Romani, R., Saracchi, M., & Covarelli, L. (2023). Impact of Enniatin and Deoxynivalenol Co-Occurrence on Plant, Microbial, Insect, Animal and Human Systems: Current Knowledge and Future Perspectives. Toxins, 15(4), 271. https://doi.org/10.3390/toxins15040271