Fusarium verticillioides contamination patterns in Northern Italian maize during the growing season

Fusarium verticillioides, often found in maize kernels, is the major fungal colonizer of maize in Northern Italy. The fungus can cause plant diseases, or grow endophytically and synthetize mycotoxins. Ear rot caused by F. verticillioides may reduce crop yield. Fumonisins produced by the fungus may harm humans and animals. In order to gather information on contamination patterns of F. verticillioides under field conditions, the current study assessed the isolation frequency percentages (IFs) of the fungus during different growth stages (GS) of four maize hybrids (Arma, Costanza, Kubrick and Tucson) cultivated in Northern Italy. Fusarium verticillioides contamination was detected in all the examined plants and in maize crop residues, but IF levels varied depending on the GS. The fungus colonized all the residues of maize plant organs, and ear debris were the preferential survival sites. Fusarium verticillioides was the major fungal contaminant at GS 00, in all seed lots with the only exception of Tucson hybrid. At the seedling stage GS 13, a similar isolation pattern was observed, but with lower IFs than in the correspondent seedlings grown in aseptic conditions: roots and mesocotyls were more contaminated than leaves. In plants before silking (GS 53), F. verticillioides contamination was localized in the basal organs. At maturity (GS 89), however, a general increase of IFs was observed in all organs. Since glumes and husks were the most contaminated organs, silks can be considered the most important pathways for F. verticillioides infection. The present study analyzes the endemic presence of F. verticillioides in Northern Italian fields and suggests further research of resistance factors in silks and husks as to indicate possible mechanisms for reducing fungal contamination.