Fumonisin B1 accumulation and severity of fusarium ear rot and gibberella ear rot in food-grade corn hybrids in Ontario after inoculation according to two methods

Abstract

Fusarium verticillioides and Fusarium graminearum are pathogens of corn causing fusarium ear rot and gibberella ear rot, respectively. The mycotoxins fumonisin B1 (FB1) and deoxynivalenol (DON) are produced by F. verticillioides and F. graminearum, respectively, and commercial millers monitor the levels of these toxins in corn to avoid problems with contamination in finished foods. The objectives of the present study were: (1) to evaluate the susceptibility of corn hybrids to F. graminearum and F. verticillioides, following silk-channel or kernel-wounding inoculations, (2) to evaluate the variability in FB1 production among food-grade corn hybrids, following silk or wound inoculation with F. verticillioides, and (3) to determine the association between the severity of fusarium ear rot and FB1 to see if visual ratings of fusarium ear rot are predictive of the tendency of corn hybrids to accumulate FB1. The experiments were conducted in the field from 1999 to 2002 with different sets of commercial hybrids each year. Mean fusarium ear rot severity and FB1 accumulation varied among years regardless of the inoculation method. Severity of fusarium ear rot and gibberella ear rot (rating on a scale of 1–7) varied respectively from 1.5 to 2.7 and 1.8 to 3.9, with silk inoculation, and from 2.0 to 2.3 and 2.8 to 4.2, with wound inoculation. For a same inoculation method, hybrids responses differed between F. graminearum and F. verticillioides inoculations, likely influenced by the different environmental conditions favoured by each fungus. There was a high level of variation in FB1 accumulation among the hybrids within each year; for example, FB1 accumulation across hybrids grown under the same environmental conditions ranged from not detected to 211.2 ppm in 2001. Severity of fusarium ear rot and FB1 accumulation after wound inoculation with F. verticillioides were correlated, suggesting that severity symptoms of fusarium ear rot after wound inoculation might be useful to select hybrids that are less likely to accumulate FB1.