|MURRAY, SETH - Texas A&M Agricultural Experiment Station|
|XU, WENWEI - Texas A&M Agricultural Experiment Station|
|PERKINS, ANDY - Mississippi State University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2014
Publication Date: 7/1/2015
Citation: Warburton, M.L., Tang, J.D., Windham, G.L., Hawkins, L.K., Murray, S., Xu, W., Boykin, D.L., Perkins, A., Williams, W.P. 2015. Genome wide association mapping of Aspergillus flavus and aflatoxin accumulation resistance in maize. Crop Science. 55:1-11, doi:10.2135/cropsci2014.6.0424.
Interpretive Summary: Corn is a valuable commodity used for industrial purposes, as a feed grain, and as a food staple around the world. It is susceptible to accumulation of a toxin produced by fungi in the genus Aspergillus. This aflatoxin is among the most lethal naturally occurring substances. It is potentially lethal to humans and animals in small doses and, even in extremely small doses, an immune suppressant and carcinogen. The development of corn lines that are resistant to infection by the fungus and/or production of the toxin would alleviate the problem in an efficient and very economical manner for farmers. Two types of genetic mapping complement each other and help scientists to identify genes that cause the favorable trait in different organisms. In maize, we have applied these techniques, association mapping and linkage mapping, to identify four genes with a very high probability of causing resistance to aflatoxin accumulation, and 25 more genes that are very good candidates for further study. These 29 total genes can soon be used to breed new resistant maize lines and hybrids in the most efficient manner possible.
Technical Abstract: Contamination of maize with aflatoxin, produced by the fungus Aspergillus flavus, has severe health and economic consequences. Efforts to reduce aflatoxin accumulation in maize have focused on identifying and selecting germplasm with natural host resistance factors, and several maize lines with significantly reduced aflatoxin accumulation have been identified. Past linkage mapping studies have identified quantitative trait loci (QTL) that consistently reduce aflatoxin levels in maize. In addition, an association mapping panel of 300 maize inbred lines was previously created specifically for the dissection of aflatoxin accumulation resistance. Here we report the results of a genome-wide association mapping study using this panel of test-crossed maize hybrids. Each of the inbred parents of the test-crossed hybrids was genotyped by sequencing (GBS) to generate 261,184 robust single nucleotide polymorphisms (SNPs), and the entire panel was phenotyped for aflatoxin accumulation following inoculation with A. flavus in multi-location, replicated field trials. Results uncovered 117 SNPs associated with aflatoxin accumulation in one or more environments in the association panel at a probability level between 9.78 x 10-6 and 2.87 x 10-10. Ten SNP-trait associations were found with a false discovery rate of less than 10% (p < 3.83 x 10-7). These SNPs fell within the sequence of four uncharacterized genes. Functional variants in 24 other genomic regions showing high association values over more than one environment were also highlighted. These genes are undergoing validation studies and will be of use to dissect the resistance to aflatoxin accumulation and improve this trait.