Resistant corn varieties to pre-empt aflatoxin

  • 20th March 2020
  • by secretary
ARS molecular geneticist Marilyn Warburton
and geneticist Paul Williams tag corn plants identified in the lab
as having molecular markers associated with resistance to
Aspergillus flavus and aflatoxin accumulation.
Photo by Stephen Ausmus.

18 March 2020. World Grain. New tool aims to identify important crop traits. A new computer application is working to speed the search for genes that underpin important crop traits, like high yield, seed quality and resistance to pests, disease or adverse environmental conditions.

Created by scientists at the US Department of Agriculture’s (USDA) Agricultural Research Service, the Pathway Association Studies Tool (PAST) app allows users to build on the results of genome-wide association studies (GWAS) of crops. GWAS takes a broad look at a crop plant’s genome for marker regions called single nucleotide polymorphisms (SNPs).

Finding SNP markers near the gene or genes encoding a desired trait can flag the genomic whereabouts of those genes and help plant breeders follow the trait’s inheritance and expression. This makes it easier to select plants that have the desired trait and develop new, better varieties from them for producers.

Marilyn Warburton, a geneticist with ARS’s Corn Host Plant Resistance Research Unit (CHPRRU) at Mississippi State, Mississippi used both GWAS and PAST which has led to the identification of genes in corn plants for resistance to the corn earworm (a caterpillar pest) and Aspergillus flavus, a greenish mold that produces a carcinogen called aflatoxin. Unchecked, corn earworms feed on the corn plant’s silks and kernels, causing damage that fosters Aspergillus growth and aflatoxin contamination.

According to the ARS, corn or other grains with aflatoxin levels exceeding 20 parts per billion cannot be sold for human consumption, and the grains’ use for animal feed is restricted. In the United States, outbreaks of Aspergillus molds that produce the carcinogen inflict more than $200 million annually in economic losses for corn and $300 million for peanuts and other crops combined.

Warburton’s research is part of a broader effort at CHPRRU together with Mississippi State University (MSU) collaborators to pre-empt aflatoxin on multiple fronts — with plantings of resistant corn varieties being a keystone defense.