Fusarium species complex on maize in Switzerland: occurrence, prevalence, impact and mycotoxins in commercial hybrids under natural infection

The Fusarium species complex of maize kernels and stem pieces as well as mycotoxin contamination of commercial grain maize hybrids for animal feed were evaluated in Switzerland. Throughout 2 years, natural Fusarium infection varied significantly between the years and the locations and it ranged from 0.4% to 49.7% for kernels and from 24.2% to 83.8% for stem pieces. Using the agar plate method, 16 different Fusarium species were isolated from kernels and 15 from stem pieces. The Fusarium species composition, prevalence and impact differed between the north and the south and between kernel and stem piece samples. The dominant species on kernels in the north were F. verticillioides (32.9%), F. graminearum (31.3%), F. proliferatum (7.3%) and F. crookwellense (7.1%), in the south F. verticillioides (57.1%), F. subglutinans (24.6%), F. proliferatum (14.8%) and F. graminearum (1.5%) and on stem pieces F. equiseti (36.0%), F. verticillioides (20.1%), F. graminearum (9.5%), F. crookwellense (6.2%) and F. subglutinans (6.2%). In the south, fumonisin concentration of most hybrids exceeded guidance values for animal feed. Other Fusarium species isolated were F. avenaceum, F. culmorum, F. oxysporum, F. poae, F. sambucinum, F. semitectum, F. sporotrichioides, F. solani, F. tricinctum and F. venenatum. Maize hybrids varied in their susceptibility to Fusarium infection. Because of the high diversity of Fusarium species encountered in Switzerland representing a high toxigenic potential, we propose to screen maize hybrids for resistance against various Fusarium species and examine maize produce for several mycotoxins in order to ensure feed safety.