Combining ability of experimental maize lines for yield and aflatoxin in the southeastern United States

Authors: Knoll, Joseph - Joe; Perla, Trevor; Krakowsky, Matthew; Guo, Baozhu

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2023
Publication Date: 7/14/2023
Citation: Knoll, J.E., Perla, T.J., Krakowsky, M.D., Guo, B. 2023. Combining ability of experimental maize lines for yield and aflatoxin in the southeastern United States. Crop Science. 63:2793-2806. https://doi.org/10.1002/csc2.21050.
DOI: https://doi.org/10.1002/csc2.21050

Interpretive Summary: Aflatoxin contamination of maize grain presents risks to animal and human health and causes economic losses for growers, particularly in the southeastern United States. Development of hybrids with genetic resistance to aflatoxin contamination by the fungus Aspergillus flavus will help to minimize these risks. Two crossing experiments were conducted to evaluate yield, agronomic traits, and aflatoxin in maize hybrids. In Exp. 1, 18 aflatoxin-resistant (GT) lines were each crossed to 6 testers. In Exp. 2, 13 of the same lines were each crossed to 10 different testers. Each experiment was conducted for two years at Tifton, GA and commercial check hybrids were included for comparison. Ears were inoculated with a strain of A. flavus that is known to produce high aflatoxin by the side-needle technique 14 d after silking. Aflatoxin was quantified in the harvested grain. Heritability (the portion of variation due to genetics) for aflatoxin was low in Exp. 1 (H2 = 0.09) but was higher in Exp. 2 (H2 = 0.27). Heritability was high for traits plant height (H2 = 0.49 – 0.51) and days to silking (H2 = 0.54 – 0.72). Among experimental lines, GT1209 and GT1309 had consistent positive general combining ability (GCA) for yield, which means hybrids of these lines tended to yield greater than average. Hybrids of GT1203 and GT1204 had consistently lower than average aflatoxin. Significant GCA effects, both positive and negative, for aflatoxin were also observed among testers in both experiments. Some experimental hybrids had yields that were comparable to commercial checks while also having lower aflatoxin, demonstrating that progress is being made in improvement of both traits in maize hybrids adapted to the Southern United States.

Technical Abstract: Aflatoxin contamination of maize (Zea mays L.) grain presents risks to animal and human health and causes economic losses for growers, particularly in the southeastern United States. Development of hybrids with genetic resistance to aflatoxin contamination by Aspergillus flavus will help to minimize these risks. Two NC Design II crossing experiments were conducted to evaluate yield, agronomic traits, and aflatoxin in maize hybrids. In Exp. 1, 18 aflatoxin-resistant (GT) lines were each crossed to 6 testers. In Exp. 2, 13 of the same lines were each crossed to 10 different testers. Each experiment was conducted for two years at Tifton, GA and commercial check hybrids were included for comparison. Ears were inoculated with A. flavus isolate NRRL 3357 by side-needle technique 14 d after silking. Aflatoxin was quantified after harvest. Broad sense heritability for aflatoxin was low in Exp. 1 (H2 = 0.09) but was higher in Exp. 2 (H2 = 0.27). Heritability was high for traits plant height (H2 = 0.49 – 0.51) and days to silking (H2 = 0.54 – 0.72). Among experimental lines, GT1209 and GT1309 had consistent positive general combining ability (GCA) for yield, whereas GT1203 and GT1204 had consistent negative (favorable) GCA for aflatoxin. Significant GCA effects, both positive and negative, for aflatoxin were also observed among testers in both experiments. Some experimental hybrids had yields that were comparable to commercial checks while also having lower aflatoxin, demonstrating that progress is being made in improvement of both traits in maize hybrids adapted to the Southern United States.