|Williams, William - Paul|
Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2007
Publication Date: 4/1/2007
Citation: Gardner, H.D., Williams, W.P., Windham, G.L. 2007. Diallel analysis of aflatoxin accumulation in maize. Field Crops Research. 102:60-63.
Interpretive Summary: Aflatoxin produced by the fungus Aspergillus flavus can contaminate corn and has caused much concern among consumers. This toxin poses a serious economic threat to corn producers in the United States. To prevent the occurrence of aflatoxin in grain, scientists are trying to find corn lines that are resistant to aflatoxin accumulation. The objectives of this study were to (1) evaluate aflatoxin accumulation in grain harvested from eight corn lines and from every possible cross between these lines, (2) determine which corn lines and which single-crosses between the corn lines would yield aflatoxin-resistant grain, and (3) determine the importance of the environmental influence on aflatoxin accumulation in the harvested corn. The tests showed that aflatoxin accumulation in the corn grain was dependent upon the genetic makeup of the grain as well as the environmental conditions. Identification of inbred lines that exhibit high levels of resistance to aflatoxin contamination, both as lines per se and in crosses with other lines, will be useful in the production of aflatoxin-resistant commercial corn hybrids. Resistance that is expressed under a wide range of environments will provide stability in the hybrids.
Technical Abstract: Since its discovery in numerous feedstuffs, aflatoxin, a carcinogenic compound produced by the fungus Aspergillus flavus Link ex Fries, has caused much concern among consumers and producers alike. As this toxin poses a serious economic threat to maize (Zea mays L.) producers of the Southeast and Midwest regions of the USA, evaluations of maize lines aimed at identifying germplasm resistant to aflatoxin accumulation have been conducted. The objectives of this study were to (1) evaluate aflatoxin accumulation in grain harvested from eight open-pollinated inbred lines and from a diallel cross of these lines, (2) determine which inbreds had general and specific combining abilities that would yield aflatoxin-resistant grain, and (3) determine the significance of the environmental influence on aflatoxin accumulation in the harvested grain. In the inbred and diallel evaluations, four resistant and four susceptible maize lines were allowed to open pollinate. The primary ears were inoculated with an A. flavus spore suspension. Following harvest, the aflatoxin content was determined from samples of grain taken from the inbred and hybrid plants. Analyses performed using SAS General Linear Models (GLM) and DIALLEL-SAS determined that significant GCA, SCA, and SCA x year effects were influencing aflatoxin accumulation. The inbred line Mp313E had significantly less aflatoxin accumulation, but didn’t combine with other lines as Mo 8W did to significantly reduce aflatoxin levels. Mp339, SC212M, and Ab24E, however, demonstrated aflatoxin susceptibility as both inbreds and single cross hybrids. Reliable prediction of hybrid performance was also shown to be difficult given the significant interaction between the hybrid plant and the environment as well as epistatic interactions that could potentially be acting on the grain.