Sequential distribution of the mycotoxin deoxynivalenol in wheat spikes after inoculation with Fusarium graminearum

One central spikelet of spring wheat (Triticum aestivum) cv. Roblin spikes was inoculated with macroconidia of Fusarium graminearum and the entire spikes were harvested at 2- to 4-day intervals from 2 to 25 days after inoculation. The spikes were dissected and the amount of deoxynivalenol (DON) in each spikelet and in each internode of the rachis was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. High concentrations of DON were first detected in the inoculated spikelets, 4 days after inoculation. DON concentrations in the spikelets below the inoculation point eventually reached 500-600 ppm while the corresponding internodes of the rachis contained 1000-1200 ppm. Much lower amounts of DON were found in spikelets and rachis above the inoculation point.