Identification and mapping of new sources of resistance to aflatoxin accumulation in maize

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Maize (Zea mays L.) susceptibility to ear rot and aflatoxin accumulation by Aspergillus flavus (Link:Fr) has caused significant economic losses for farmers in the U.S. over the past 30 years. Aflatoxin outbreaks are generally associated with high temperatures and low moisture levels common to the southern U.S. To identify aflatoxin accumulation resistance quantitative trait loci (QTL) and linked markers for marker-assisted breeding (MAB), a genetic mapping population of F2:3 family genotypes, increased by sib-mating, was developed from Mp717, a maize inbred resistant to aflatoxin accumulation, and NC300, a southern-adapted inbred with low levels of resistance and desirable agronomic traits. Replicated trials of the mapping population were subjected to A. flavus inoculation in Tifton, GA and Starkville, MS in 2004 and 2005. Quantitative trait loci on all chromosomes, except chromosomes 4, 6, and 9, were identified, and individual QTL explained from less than 1% to a maximum of 11% of the phenotypic variance in aflatoxin accumulation in grain. Both Mp717 and NC300 were found to contribute resistance to aflatoxin accumulation in the F2:3 families and overall QTL effects differed because of environmental conditions. Many of these loci were distinct from previously identified QTL, which confirmed Mp717 as a novel source of aflatoxin resistance.

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