CONCENTRATION OF DEOXYNIVALENOL IN SINGLE KERNELS AND VARIOUS TISSUESOF WHEAT HEADS

An improved method of extraction of deoxynivalenol (DON) from small sa mples of plant tissues is described. Using a ball mill, the extraction time was reduced from 60 minutes to 1 minute and the amount of monocl onal antibodies required for a reliable competitive direct (CD)-ELISA was reduced from 100 mu g/mL to 5 mu g/mL. Using this method, we analy sed the kernels, chaff. rachis and peduncle of individual heads of whe at plants that had been field-inoculated with Fusarium graminearum. Th e DON concentration varied considerably among the same tissues from di fferent plants. The median concentration of DON was highest in the rac his (93 ppm). followed by chaff (50 ppm), kernels (25 ppm), and pedunc les (16 ppm). We also determined the DON concentration in single kerne ls obtained from a naturally-affected commercial wheat field. One hund red each of visibly unaffected (''normal-looking'') kernels, shrivelle d kernels, and fusarium damaged (''white tombstone'' and ''pink tombst one'') kernels were analysed. DON was detected in about 50% of the nor mal-looking and shrivelled kernels, but typically at concentrations of 5 ppm or less. DON levels in tombstone kernels varied from less than 1 ppm to 600 ppm, with a mean of 275 ppm and 118 ppm in pink tombstone and white tombstone kernels, respectively.