Quantitative trait loci contributing resistance to aflatoxin accumulation in the maize inbred Mp313E

Aflatoxin is a carcinogenic and toxic compound produced by the fungus Aspergillus flavus (Link:fr) that can be found at detrimentally high concentrations in maize (Zea mays L.) grain. Screening has led to the discovery of sources of resistance to aflatoxin accumulation in maize, but associated poor agronomic characteristics and complex inheritance have limited transfer of resistance to elite inbreds. A set of 210 F2:3 families derived from a cross between inbred lines Mp313E (resistant) and B73 (susceptible) was evaluated in replicated trials in four environments for resistance to aflatoxin accumulation. Families were also genotyped using simple sequence repeat (SSR) markers to develop a genetic map for quantitative trait loci (QTL) analysis. Composite interval mapping (CIM) was used to identify 2, 3, 5, and 3 QTL within the tests at Stoneville (2000) and Mississippi State (2000, 2001, 2002), respectively. The QTL were primarily additive in nature, with Mp313E contributing to reduced aflatoxin concentration in all but one case. Two QTL regions were significant in at least three environments. The afl3 locus, represented by marker bnlg371, was located on chromosome two and accounted for 7 to 18% of variation in aflatoxin levels depending on environment. The afl5 locus, represented by marker bnlg2291, was located on chromosome four, with explained variance ranging from 8 to 18%. This QTL has been noted in earlier studies whereas afl3 is new. Identified QTL confirm important regions influencing aflatoxin accumulation previously identified and present new ones of equal effect.