Confirmation of QTL Reducing Aflatoxin in Maize Testcrosses

Abstract

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.

QTL Mapping for Grain Yield, Flowering Time, and Stay‐Green Traits in Sorghum with Genotyping‐by‐Sequencing Markers

“…Testcross progenies show reduced variation for a trait because of the contribution of only one allele from the corresponding RIL population. The QTLs detected in the RIL testcrosses are different from the RILs due to dominance effect of the heterozygous loci as well as epistasis between locus and genetic background ( Jines et al, 2007;Kerns et al, 1999;Mayfield et al, 2011). Several QTLs reported in the study are unique to the study and the QTLs that coincided with earlier studies were described.…”

Aflatoxin Resistance in Maize: What Have We Learned Lately?

“…Eight QTL mapping experiments on A. flavus or aflatoxin resistance [35][36][37][38][39][40][41][42] and one additional on ear rot due to A. flavus [43] have been published to date. Most of these QTL studies have reported multiple QTL, most of which have been found in only one environment, and the majority of the QTL each account for less than 5% of the phenotypic variation observed in the population and the environment in which it was measured.…”

Quantitative Trait Loci Influencing Mycotoxin Contamination of Maize: Analysis by Linkage Mapping, Characterization of Near‐Isogenic Lines, and Meta‐Analysis

“…Ear rot was the subject of a recent meta-analysis (Xiang et al, 2010), but the study did not include data for resistance to mycotoxin accumulation, and we are not aware of prior studies reporting meta-analysis of aflatoxin resistance. With the recent publication of three new QTL mapping studies on resistance to aflatoxin accumulation and an additional study presented here, the number of available studies has increased, making a metaanalysis of this trait more relevant (Mayfield et al, 2011;Warburton et al, 2010;Willcox et al, 2013).…”

“…The largest of these (representing the most QTL) was mqtl5 on chromosome 4, which was formed by four QTL for resistance to aflatoxin accumulation (Supplemental Table S3). These included qbAFL4.08, located near marker PHM3637 in maize bin 4.08 in our stepwise regression analysis, and QTL from populations Mp313E × B73 (Brooks et al, 2005), B73O2/O2 × CML616 (Mayfield et al, 2011), and Mp313E × Va35 (Willcox et al, 2013).…”