Fungal interaction in maize ears in field during the growing season

Maize is an important crop cultivated worldwide that may be infected by several mycotoxigenic fungi. They interact and the dominant fungus depends mainly on meteorological conditions during the growing season; other factors linked to the plant and the cropping system can contribute. In Italy, the major mycotoxigenic fungi found on ripening maize are Aspergillus flavus, Fusarium verticillioides and, to a lower extend, F. graminearum. These fungi produce different mycotoxins, in particular, aflatoxins (AFs), fumonisins (FBs) and deossinivalenol (DON), respectively. Many studies have been done on fungi in field, but poor information is available regarding co-occurrence of fungi and, consequently, on the effect of their interaction on mycotoxins production. In 2016, maize ears in a field crop were artificially inoculated after silk emergence with the 3 mentioned fungi, alone or in co-presence. Ear samples were collected every 14 days up to harvest time. When fungi were single-inoculated, the highest incidence resulted after 42 days for F. verticillioides and after 28 days for A. flavus and F. graminearum. When co-inoculated, fungi showed a different behaviour; F. verticilliodes showed the highest incidence after 28 days and A. flavus and F. graminearum only after 42 days, irrespective of the co-inoculated species. Regarding mycotoxins, A. flavus always produced more AFs when competitors were present while FBs and DON production was faster or increased only when Fusaria co-occurred. Data obtained will be useful to support/validate predictive models for fungal growth and mycotoxin production in field with co-occurring fungi, more frequent in recent years due to climate change.