Submitted to: Journal of Genetics and Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/2/2004
Publication Date: 12/1/2003
Citation: Williams, W.P., Windham, G.L., Buckley, P.M. 2003. Aflatoxin accumulation in maize after inoculation with Aspergillus flavus and infestation with southwestern corn borer. Journal of Genetics and Breeding. 57:365-370. Interpretive Summary: Aflatoxin is produced by the fungus Aspergillus flavus and occurs naturally in corn. Dietary exposure to aflatoxin is a major cause of some types of liver cancer. Corn containing more than 20 ppb of aflatoxin is banned from interstate commerce. High temperatures, seasonal drought, and insect damage make corn produced in the South especially vulnerable to aflatoxin contamination. Growing corn hybrids with genetic resistance to aflatoxin contamination is generally considered the most promising way to reduce aflatoxin contamination. Although corn hybrids with adequate resistance to aflatoxin to withstand the frequently encountered environmental stresses in the South are not available commercially, germplasm with resistance to both aflatoxin contamination and insect damage has been identified. This investigation was undertaken to investigate the inheritance of resistance to aflatoxin contamination in crosses among lines selected directly for resistance to aflatoxin contamination, lines selected for resistance to southwestern corn borer, and lines susceptible to both. The genetic analysis indicated that two aflatoxin resistant lines, Mp313E and Mp92:673, contributed significantly to higher levels of aflatoxin resistance in hybrids. Interesting, hybrids with Mp496 and Mp716, two of the southwestern corn borer resistant lines, as parents exhibited reduced levels of aflatoxin. Incorporating resistance to both fungal infection/aflatoxin accumulation and southwestern corn borer in corn hybrids grown in the South could be an effective method of reducing aflatoxin contamination.
Technical Abstract: Aflatoxin is a potent carcinogen produced by the fungus Aspgergillus flavus Link: Fr. Drought, high temperatures, and insect damage are associated with high levels of aflatoxin accumulation in maize, Zea mays L. Plant resistance is generally considered a desirable way of reducing aflatoxin contamination. Germplasm lines with resistance to aflatoxin contamination have been developed. A nine-parent diallel cross was made using three lines with resistance to southwestern corn borer, Diatraea grandiosella Dyar: three lines with resistance to aflatoxin contamination; and three lines susceptible to both aflatoxin contamination and southwestern corn borer. The resulting single cross hybrids were evaluated for aflatoxin contamination following inoculation with A. flavus and infestation with southwestern corn borer. General combining ability (GCA) was a highly significant source of variation in the inheritance of resistance to aflatoxin contamination; specific combining ability was not significant. Estimates of GCA effects indicated that Mp313E and Mp92:673, lines selected for aflatoxin resistance, contributed significantly to reduced aflatoxin contamination. Hybrids with Mp496 and Mp716, two of the southwestern corn borer resistant lines, also exhibited levels of aflatoxin contamination. These lines would be useful as sources of resistance in the development of maize hybrids with resistance to aflatoxin contamination.