Identification and mapping of new sources of resistance to AFL atoxin accumulation in maize

Abstract

Maize (Zea mays L.) susceptibility to ear rot and afl atoxin accumulation by Aspergillus flavus (Link:Fr) has caused signifi cant economic losses for farmers in the U.S. over the past 30 years. Afl atoxin outbreaks are generally associated with high temperatures and low moisture levels common to the southern U.S. To identify afl atoxin accumulation resistance quantitative trait loci (QTL) and linked markers for markerassisted breeding (MAB), a genetic mapping population of F2:3 family genotypes, increased by sib-mating, was developed from Mp717, a maize inbred resistant to afl atoxin 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 identifi ed, and individual QTL explained from less than 1% to a maximum of 11% of the phenotypic variance in afl atoxin accumulation in grain. Both Mp717 and NC300 were found to contribute resistance to afl atoxin accumulation in the F2:3 families and overall QTL effects differed because of environmental conditions. Many of these loci were distinct from previously identifi ed QTL, which confi rmed Mp717 as a novel source of afl atoxin resistance. © Crop Science Society of America.