Identification of quantitative trait loci contributing resistance to aflatoxin accumulation in maize inbred Mp715

Authors: Smith, Jesse; Williams, William; Windham, Gary; XU, WENWEI - Texas A&M University; Warburton, Marilyn; BHATTRAMAKKI, DINAKAR - Corteva Agriscience

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2019
Publication Date: 6/11/2019
Citation: Smith, J.S., Williams, W.P., Windham, G.L., Xu, W., Warburton, M.L., Bhattramakki, D. 2019. Identification of quantitative trait loci contributing resistance to aflatoxin accumulation in maize inbred Mp715. Molecular Breeding. 39:91. https://doi.org/10.1007/s11032-019-0997-0.
DOI: https://doi.org/10.1007/s11032-019-0997-0

Interpretive Summary: Aflatoxin is a potent toxin produced by the fungus Aspergillus flavus. Aspergillus flavus is a pathogen of corn (Zea mays), and grain colonized by A. flavus can be contaminated by aflatoxin. Aflatoxin contaminated grain presents a potential economic loss to producers where aflatoxin is monitored, and a health risk to consumers where it is not monitored. Breeding corn with resistance to colonization by A. flavus and accumulation of aflatoxin is one strategy to reduce aflatoxin contaminated grain. Mp715 is a resistant line developed by USDA-ARS scientists, but its resistance is based on many genes, with small individual effects. To help plant breeders utilize the genetic resistance din Mp715, this study mapped regions of the maize genome associated with variation in susceptibility/resistance in a population of 250 250 families derived from a cross between Mp715 and the susceptible genotype Va35. The 250 families were genotyped with 1200 molecular markers and evaluated for aflatoxin accumulation in the grain in field studies conducted in four environments. When the data was analyzed across all four environments, genetic variation at two genomic regions, one on chromosome 6 (6.06) and one on chromosome 7 (7.03) accounted for nearly 50% of the phenotypic variance under genetic control. By selecting for these two chromosomal regions using molecular, plant breeders could move the resistance present in Mp715 into other corn germplasm lines. These lines could then be used in developing corn hybrids with genetic resistance to aflatoxin accumulation that would be available to farmers.

Technical Abstract: Aflatoxin is a mycotoxin produced by the fungus Aspergillus flavus (Link:Fr), an opportunistic ear-rot pathogen of maize (Zea mays L. ssp. mays). Pre-harvest contamination of maize grain with aflatoxin is a chronic problem worldwide and particularly in the southeastern U.S. Quantitative trait loci (QTL) were mapped by multiple interval mapping (MIM) in a population consisting of 250 F2:3 lines derived from the cross Mp715 x Va35. Mp715 is resistant to the accumulation of aflatoxin and Va35 is susceptible. The population was genotyped with 1,200 single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) molecular markers and phenotyped for accumulation of total aflatoxins under artificial inoculation in four environments. Both parents contributed resistance alleles in every environment. Multiple QTL with the beneficial alleles derived from Va35 were consistently observed on the short arm of chromosome 1. Two QTL in bins 6.06 and 7.03 were the most promising for the marker-assisted introgression of the resistance present in Mp715. Those two QTL were the most consistent across individual environments and together were responsible for nearly 30% of the phenotypic variance and nearly 50% of the genotypic variance when data was combined across all four environments. Mp715 was the source of the beneficial aflatoxin-reducing allele for other smaller effect QTL in bins 3.03, 4.08, 8.05, and 10.05 but none of those QTL accounted for more than 10% of the phenotypic variance.