Relationship between European Corn Borer injury, Fusarium proliferatum and F. subglutinans infection and moniliformin contamination in maize

The European Corn Borer (ECB), Ostrinia nubilalis (Hübner), plays an important role in promoting Fusarium infection and fumonisin production in maize kernels. Moniliformin (MON) is a mycotoxin that is usually found in association with fumonisins (FB), and as a consequence ECB is also expected to play a role in MON contamination. The aim of the current study was to investigate the influence of ECB activity on MON contamination and on the fungi responsible for its contamination. A comparison has been made between maize infected naturally by insect larvae and protected maize, from 2008 to 2010 in North-West Italy; the latter was obtained by positioning an entomological net at the end of maize flowering. The F. proliferatum infection of the maize grain was higher in each growing season than that caused by F. subglutinans, although both species were significantly increased due to the ECB damage to the maize ears. The ECB activity significantly increased the MON content 26-fold in 2008 from 43 to 1137 µg kg-1, 25-fold in 2009 from < LOQ to 77 µg kg-1 and 94-fold in 2010 from 6 to 564 µg kg-1. The relationship between the MON content and the Fusarium species producers of MON was closer for F. proliferatum (R2 = 0.93, P < 0.001) than for F. subglutinans (R2 = 0.68, P < 0.001). An in vitro assay was carried on in order to assess the toxigenic capacity of different F. proliferatum and F. subglutinans strains isolated from a field experiment and artificially inoculated on a maize substrate. On average, the F. proliferatum isolated strains showed a significantly higher (P < 0.001) toxigenic capacity than the F. subglutinans strains. In conclusion, the combination of the high toxigenic capacity of F. proliferatum, and its more frequent occurrence and greater intensity in the field make it possible to state that the production of MON in maize temperate areas, such as North Italy, is mainly due to F. proliferatum infections and is closely linked to the injury caused by ECB larvae.