Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 6/1/2005
Publication Date: 12/1/2005
Citation: Williams, W.P., Windham, G.L., Buckley, P.M. 2005. Enhancing maize with resistance to Aaspergillus flavus infection and aflatoxin accumulation. In: Abbas, Hamed K., editor. Aflatoxin and Food Safety. Boca Raton, FL: CRC Press. p. 379-394. Interpretive Summary: Aflatoxin, which is produced by the fungus Aspergillus flavus, is toxic to livestock and carcinogenic to humans. Aflatoxin contamination of corn grain is a major threat to profitable corn production in the South. Although growing corn hybrids with genetic resistance to fungal infection and aflatoxin accumulation is widely considered the best method for reducing contamination, hybrids are not currently available to farmers. Extensive germplasm screening at Mississippi State has resulted in the identification and release of three germplasm lines with resistance to aflatoxin contamination. These screenings have also identified other germplasm lines as potentially useful sources of resistance. Using both conventional breeding methods and molecular marker assisted selection, research is currently underway to combine aflatoxin resistance from different sources and good agronomic qualities in germplasm lines that will be released. These lines will then be used in commercial corn breeding programs to produce aflatoxin resistant corn hybrids. The production of such hybrids and their availability to farmers will reduce the threat of aflatoxin contaminated grain.
Technical Abstract: Preharvest kernel infection by Aspergillus flavus and the subsequent accumulation of aflatoxin in maize grain are chronic problems in the southeastern United States. Aflatoxin is a natural carcinogen, and its presence markedly reduces the value of grain. Losses to aflatoxin contamination reach devastating levels some years. Development and deployment of maize hybrids with resistance to aflatoxin contamination is generally considered the most feasible method of reducing or eliminating the problem. Research to address the aflatoxin problem was initiated by USDA-ARS at Mississippi State, MS, in the late 1970s. The goals of the research were to identify and develop aflatoxin-resistant maize germplasm. Reliable techniques for screening germplasm were developed, and, germplasm from numerous sources was screened. The release of Mp313E in 1988 was the first release of maize germplasm with resistance to aflatoxin contamination. Two other germplasm lines, Mp420 and Mp715, were released in 1991 and 1999, respectively. Additional germplasm lines have been developed, but not yet released. Efforts are currently underway to identify other sources of resistance. When used in crosses with other lines, the aflatoxin-resistant lines markedly reduce the level of aflatoxin contamination in the resulting hybrids. Several lines that were selected for resistance to insect damage also exhibited reduced levels of aflatoxin contamination. Analysis of a diallel cross indicated that general combining ability was a significant source of variation in the inheritance of resistance to aflatoxin contamination. Efforts to combine resistance to aflatoxin combination and agronomic qualities using both conventional breeding methods and molecular marker assisted selection have been initiated.