and Co-Occurrence Influences Plant and Fungal Transcriptional Profiles in Maize Kernels and In Vitro

Climate change will increase the co-occurrence of and , along with their mycotoxins, in European maize. In this study, the expression profiles of two () genes and four mycotoxin biosynthetic genes, and , fumonisin pathway, and and , aflatoxin pathway, as well as mycotoxin production, were examined in kernels and in artificial medium after a single inoculation with or or with the two fungi in combination. Different temperature regimes (20, 25 and 30 °C) over a time-course of 21 days were also considered. In maize kernels, genes showed the strongest induction at 25 °C in the earlier days post inoculation (dpi)with both fungi inoculated singularly. A similar behaviour was maintained with fungi co-occurrence, but with enhanced defence response at 9 dpi under 20 °C. Regarding genes, in the kernels inoculated with the maximal transcript levels occurred at 6 dpi at 25 °C. At this temperature regime, expression values decreased with the co-occurrence of , where the highest gene induction was detected at 20 °C. Similar results were observed in fungi grown in vitro, whilst presence determined lower levels of expression along the entire time-course. As concerns genes, considering both alone and in combination, the most elevated transcript accumulation occurred at 30 °C during all time-course both in infected kernels and in fungi grown in vitro. Regarding mycotoxin production, no significant differences were found among temperatures for kernel contamination, whereas in vitro the highest production was registered at 25 °C for aflatoxin B1 and at 20 °C for fumonisins in the case of single inoculation. In fungal co-occurrence, both mycotoxins resulted reduced at all the temperatures considered compared to the amount produced with single inoculation.