Aflatoxin accumulation in maize hybrids of different maturities
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The incidence and severity of preharvest aflatoxin is greater under drought conditions, which commonly occur late in the growing season of south and central Texas. To determine if early maturation could be used as a means of disease escape, aflatoxin contamination was measured in early-, intermediate-, and full-season commercial hybrids at two Texas locations, Weslaco and College Station. The early and intermediate hybrids chosen are primarily marketed in midwestern USA while the full-season hybrids are primarily marketed in southeastern USA. Hybrids were evaluated by inoculating ears 6 to 10 d after midsilk with Aspergillus flavus NRRL 3357 using the silk channel technique and measuring aflatoxin in harvested grain using the VICAM Aflatest procedure. Across locations, full-season hybrids had lower aflatoxin (mean = 777 ng g -1) levels than intermediate (mean = 1668 ng g-1) and early (mean = 1899 ng g-1) hybrids. There was an inverse correlation between silking date and aflatoxin levels at both locations (r = -0.59, P = 0. 01 at College Station and r = -0.58, P = 0.01 at Weslaco). Early and intermediate hybrids had looser husk coverage than full-season hybrids, a characteristic that was positively correlated with aflatoxin levels at both locations. At both locations, grain yield was lower with early and intermediate hybrids than with full-season hybrids. Early maturation in hybrids was insufficient by itself to reduce aflatoxin contamination, but it should be re-evaluated using early maturing hybrids that have good agronomic adaptation to these two Texas growing conditions.
