Maize maturity and the development of gibberella ear rot symptoms and deoxynivalenol after inoculation

Development of gibberella ear rot disease symptoms and the accumulation of the mycotoxin deoxynivalenol (DON) in maize ears inoculated via the silk with Fusarium graminearum was determined at various times after inoculation. Ten hybrids ranging in maturity from early to late, were inoculated with a conidial suspension in 1993 and 1994 and harvested every 2 weeks for 14 weeks after inoculation. Disease symptom evaluations were conducted on all 10 hybrids; five of these hybrids were further analysed for DON concentrations. Disease symptoms reached a maximum and stabilized by 6 weeks after inoculation, approximately at physiological maturity (35% kernel moisture) for the early hybrids and the late dent stage of maturity for later hybrids. Deoxynivalenol accumulation was correlated with symptom development but did not stabilize at 6 weeks for all genotypes. Hybrid maturity did not influence symptom development or DON accumulation, but environment did. For the evaluation of hybrids, assessments of resistance to fungal invasion and mycotoxin accumulation based on symptom development could be made much earlier than the current 12-14 week harvest time commonly used in inoculated experiments.