Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2006
Publication Date: 4/1/2006
Citation: Menkir, A., Brown, R.L., Bandyopadhyay, R., Chen, Z.-Y., Cleveland, T.E. 2006. A U.S.A – Africa collaborative strategy for identifying, characterizing, and developing maize germplasm with resistance to aflatoxin contamination. Mycopathologia. 162:225-232. Interpretive Summary: Aflatoxins are poisons produced by the fungus Aspergillus flavus after it infects agricultural commodities, such as corn. Aflatoxin contamination of corn poses serious potential economic losses in the U.S. and health hazards to humans in West Africa. SRRC and the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria initiated a collaborative breeding project to develop corn lines with resistance to aflatoxin contamination. Resistant lines from the U.S. were crossed with resistant inbred lines from IITA to generate two populations: one with a 75% U.S. genetic contribution and another with a 50% IITA and 50% U.S. contribution. After four generations of self pollination and selection, a number of lines from each group were screened at SRRC for aflatoxin accumulation using a kernel-screening assay. Several promising lines with low aflatoxin levels were selected for further field confirmation tests. Pairs of lines with common genetic backgrounds but differing in aflatoxin accumulation were also identified. These pairs are currently being compared and analyzed for protein differences to identify genes that underlie resistance to aflatoxin accumulation. Corn inbred lines with desirable agronomic traits and low levels of aflatoxin in the field will be released as sources of genes for resistance to aflatoxin production. These lines could then be used to develop lines for use by growers in the U.S. and Africa to enhance crop and grain protection and to increase profits.
Technical Abstract: Aflatoxin contamination of maize by Aspergillus flavus poses serious potential economic losses in the U.S. and health hazards to humans in West Africa. SRRC and IITA initiated a collaborative breeding project to develop maize germplasm with resistance to aflatoxin accumulation. Resistant genotypes from the U.S. and selected inbred lines from IITA were used to generate backcrosses with 75% U.S. germplasm and F1 crosses with 50% IITA and 50% U.S. germplasm. A total of 65 S4 lines were developed from the backcross populations and 144 S4 lines were derived from the F1 crosses. These lines were separated into groups and screened in SRRC laboratory using a kernel-screening assay. Large and significant differences in aflatoxin production were detected among the lines within each group. Several promising S4 lines with aflatoxin values significantly lower than their respective U.S. resistant recurrent parent or their elite tropical inbred parent were selected for resistance-confirmation tests. We found pairs of S4 lines with 75% to 94% common genetic backgrounds differing significantly in aflatoxin accumulation. These pairs of lines are currently being used for proteome analysis to identify resistance-associated proteins and the corresponding genes underlying resistance to aflatoxin accumulation. Following confirmation tests in the laboratory, lines with consistently low aflatoxin levels will be inoculated with A. flavus in the field in Nigeria to identify lines resistant to strains specific to both U.S. and West Africa. Maize inbred lines with desirable agronomic traits and low levels of aflatoxin in the field would be released as sources of genes for resistance to aflatoxin production.