A flatoxin is a hepatotoxic, carcinogenic, and immunosuppressive byproduct of the fungus, Aspergillus flavus Link, which is associated with a variety of food commodities such as maize (ZeaBr.], rice (Oryza sativa L.), wheat (Triticum aestivum L.) and peanuts (Arachis hypogaea L.), among others grown in the tropics, subtropics, and the southern United States. It continues to cause disease when contaminated grain is consumed in countries that lack regulatory programs and funding to test and control its presence

Maize (Zea mays L.) production in Texas, the southern United States, and much of the developing world is constrained by preharvest contamination from aflatoxins—potent mycotoxins produced by the fungus Aspergillus flavus. When consumed, aflatoxin can lead to impaired growth, liver cancer, or death of both humans and livestock. Because of these effects, the presence of this mycotoxin is tightly regulated in the U.S. food supply. No complete resistance to A. flavus or aflatoxin is known to exist in maize; however, multiple quantitative traits and some sources of resistance have been identified. We propose the release of three maize lines that demonstrate reduced preharvest aflatoxin accumulation. Tx736 (Reg. No. GP‐578, PI 662937) is a germplasm line derived from modified pedigree selection of a cross between Tx772, a line with reduced aflatoxin accumulation, and T246, a temperate line with good yield and Texas adaptation, backcrossed to Tx772 once. Lines Tx739 (Reg. No. GP‐579, PI 662938) and Tx740 (Reg. No. GP‐580, PI 662939) were selected by pedigree methods from S3 plants selfed out of heterotic groups A, C, and E from Agricomseeds (Santa Cruz, Bolivia). These three lines were field tested as lines per se and as testcross hybrids with introduced inoculation in multienvironmental field trials. In trials, these lines and hybrids had between 30 and 73% lower aflatoxin content than commercial checks. These germplasm lines will serve as unique sources for novel traits and alleles that reduce aflatoxin in elite temperate and subtropical maize.

Aflatoxins, produced by the fungus Aspergillus flavus Link:Fr, constrain maize (Zea mays) production in some regions. Difficulties in breeding resistance to this toxin make it a good target for quantitative trait iocus (QTL) identification and molecular-assisted breeding. Multiple QTL have been identified for aflatoxin resistance in inbred lines per se; however, it has not been determined if aflatoxin resistance QTL would be useful in hybrids or have deleterious pleiotropic effects. The objectives were to confirm the presence, in testcrosses, of QTL estimates previously identified in lines per se; estimate new QTL for reducing aflatoxin accumulations and agronomic traits in hybrids; and evaluate co-localization of QTL that suggest pleiotropic effects with measured traits. Plant height, flowering time, starch, oil, and protein were also included in the analysis. Significant environment and genetic x environment interaction were detected for most traits. Heritability estimates were equivalent to those previously reported, and no meaningful correlations were detected between aflatoxin accumulation and other traits. Ninety-three QTL were detected across 14 traits measured in five environments. Aflatoxin-reducing QTL detected in per se analyses were detected in testcrosses on chromosome 1, with new QTL detected on chromosomes 3, 4, 8, and 9. Co-localization of aflatoxin-reducing QTL detected on chromosome 9 with QTL for silking date suggests a pleiotropic effect based on avoidance or agronomics and not a resistance QTL.

Preharvest aflatoxin (AF) contamination by Aspergillus flavus Link:Fr is one of the main limitations for maize (Zea mays, L.) production in the southern USA, causing enormous economic losses and posing a risk to animal and human health. The objectives of this study were (1) to estimate aflatoxin accumulation and expression of associated traits in quality protein maize (QPM) inbreds and their testcrosses, (2) to compute their repeatabilities and correlations, and (3) to study the relationship between inbred lines and their testcrosses for aflatoxin accumulation. Forty-eight inbreds and their testcrosses plus checks were grown in one and three locations in south and central Texas, respectively. Aflatoxin concentration was evaluated in the plants following inoculation with A. flavus. Average aflatoxin concentration overall for inbreds was 286.3 ng g -1 , and for testcrosses 596.5 ng g -1 at Corpus Christi, TX, 325.1 ng g -1 at Weslaco, TX, and 105.1 ng g -1 at College Station, TX. Flinty orange inbreds developed from CIMMYT Population 69 were the least susceptible to aflatoxin accumulation in both inbreds and testcrosses at all locations. Repeatability for aflatoxin was 0.67 in inbreds at Weslaco, TX and 0.54 in testcrosses across locations. Aflatoxin in testcrosses was positively correlated both phenotycally and genotypically with endosperm texture and kernel integrity, and negatively correlated with grain yield and silking date. Less aflatoxin accumulation was associated with flinty endosperm texture, better kernel integrity, and later maturities. Association between the expression of traits in inbreds and aflatoxin in testcrosses was relatively high for endosperm texture (R 2 = 0.62), silking date (R 2 = 0.44), kernel integrity (R 2 = 0.39), and aflatoxin (R 2 = 0.60 for log ng g -1 ). It seems plausible to select for associated traits having high heritabilities and strong correlation with aflatoxin, in addition to low aflatoxin accumulation in inbreds and hybrids to reduce the risk of aflatoxin contamination.

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