MAIZE MATURITY AND THE DEVELOPMENT OF GIBBERELLA EAR ROT SYMPTOMS ANDDEOXYNIVALENOL AFTER INOCULATION

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