Plant Population Response of New Aflatoxin-Resistant Corn Hybrids in Georgia.

Pre-harvest aflatoxin contamination caused by the fungus Aspergillus flavus is a common problem in corn production under hot and humid growing conditions. New higher-yielding hybrids with improved genetic resistance to pre-harvest A. flavus infection and aflatoxin accumulation are being developed by the USDA-ARS to help minimize this risk. Experimental hybrids and commercial checks were planted at Tifton, GA in 2016 and 2017 in a split-plot experimental design with four replications. Plant spacing was the main plot factor, and hybrid was the sub-plot factor. Each sub-plot consisted of two 4.3 m rows, 0.9 m apart with a 1.8 m alley on each end. Four plant density treatments were applied: 41, 37, 34, and 31 seeds/row. With an expected germination rate of 90%, the plant spacings were approximately 11, 13, 14, and 15 cm, respectively. At 7 d after silking, A. flavus-infected corn kernels were scattered in the middle of each plot to increase inoculum. At 60 days after silking, five random ears were harvested from each plot for aflatoxin analysis. Plots were harvested by combine at maturity, and the weights of the sampled ears were added to determine final plot weights. Yields were adjusted to 15% moisture for comparison. As expected, the two commercial checks were among the highest yielders, but 11 of the experimental hybrids were not statistically different from the highest commercial check in 2016. Plant density had a slight effect on grain yield, with the lowest density (15 cm) having greater yield (6,817 kg/ha) than the 11 cm and 14 cm treatments (6,127–6,196 kg/ha). On average, planting density did not affect aflatoxin levels in the grain; however, one commercial hybrid had significantly elevated levels at the two densest planting treatments in 2016.