Characterization of Fusarium species diversity causing crown and stalk rot on maize in northern Italy.

The genus Fusarium includes many agronomically important species and toxin-producers strains, that can cause a wide range of diseases of many horticultural, cereals, ornamental, and forest crops. Fusarium spp. are worldwide distributed and reported as the main causal agents of crown and stalk rots and grain infections on corn. Crown and stalk rot development is usually developing during germination, but the disease may affect the later phases of plant growth, causing a premature senescence and lodging of the plants. In Italy, corn is affected by several species of Fusarium, so the purpose of this study was to investigate the diversity and the pathogenicity of 41 strains isolated during springs 2019 and 2020, from symptomatic seedlings collected in fields located in the provinces of Vercelli (Piedmont) and Vicenza (Veneto), and from seeds with five different geographical origins. The pathogenicity was tested, and a multi-locus phylogeny analysis, based on four genomic loci (tef1-α, rpb2, calm and tub2), was performed for 23 representative isolates. Fusarium representative strains were identified as species belonging to three species complexes. Fusarium verticillioides and F. annulatum of the Fusarium fujikuroi species complex. Fusarium commune was identified in the Fusarium nisikadoi species complex, and three different lineages in the Fusarium oxysporum species complex. Pathogenicity was confirmed for the 23 representative isolates, causing rotting on maize seedlings. This study widens our knowledge on Fusarium species on maize, and it reports F. annulatum, and two lineages of the Fusarium oxysporum species complex as corn pathogens for the first time in Italy.