Presence and correlation of Fusarium graminearum and deoxynivalenol accumulation in silage corn plant parts.

Corn silage, made from Zea mays, is a high energy feed that is important for feeding dairy cows. Plant diseases, such as those caused by Fusarium graminearum , can decrease silage corn yields and quality. Fusarium graminearum (teleomorph Gibberella zeae) is an ascomycete fungus that causes Gibberella ear and stalk rot in corn. Fusarium graminearum produces deoxynivalenol (DON), a secondary metabolite toxic to humans and animals. An understanding of the distribution of DON and F. graminearum throughout the corn plant is important for determining the quality of corn silage. A partitioned sample experiment that included two brown-midrib silage hybrids and three fungicide treatments was conducted in research plots located in Arlington, Wisconsin in 2018 and 2019. At harvest, stalk and ear parts were physically separated, dried, and ground for analysis. DON concentration (ppm) was determined using ELISA and F. graminearum DNA concentration (pg/ng) was determined using qPCR. Both DON and F. graminearum DNA were detected in all samples, demonstrating accumulation of the fungus in both stalks and ears of the plant. In 2018, DON contamination was as high as 30 ppm and varied drastically between stalks and ears. In 2019, DON concentrations were much lower (<5ppm), but were consistently higher in stalk samples than ear samples. Across all samples DON concentrations and F. graminearum accumulation were highly correlated within the separated stalk (r=0.78) and ear portions (r=0.87) but were not correlated between ears and stalks. Depending on the weather and planting conditions in a given year, either stalk infections or ear infections may occur by F. graminearum leading to subsequent DON increases in those respective parts that are independent of each other.