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United States Department of Agriculture

Agricultural Research Service

Research Project: Genetic Improvement of Maize and Sorghum for Resistance to Biotic Stress

Location: Crop Genetics and Breeding Research

Project Number: 6602-21220-017-00
Project Type: Appropriated

Start Date: May 20, 2013
End Date: May 19, 2018

Objective:
1. Identify new sources of maize germplasm with resistance to aflatoxin and insects, and identify new sources of sorghum germplasm with improved insect resistance. 1A. Evaluate exotic maize germplasm from the Germplasm Enhancement of Maize (GEM) program, International Center for the Improvement of Maize and Wheat (CIMMYT), and the U.S. maize germplasm collection for resistance to infection by Aspergillus flavus and aflatoxin contamination. 1B. Screen for resistance to ear- and kernel-feeding stink bugs, sap beetles, thrips and maize weevil in maize germplasm from the GEM, the CIMMYT, and the U.S. maize germplasm collection. 1C. Evaluate sorghum lines from the U.S. germplasm collection for anthracnose resistance. 1D. Screen for whorl-feeding fall armyworm and head-feeding sorghum midge resistance in sorghum lines from the U.S. germplasm collection. 2. Develop maize and sorghum germplasm adapted to the southeastern United States with enhanced resistance to diseases and insects. 2A. Develop maize germplasm with reduced aflatoxin accumulation, increased resistance to insects, and enhanced agronomic performance in the southern Coastal Plain region. 2B. Develop sorghum germplasm with improved disease and insect resistance and high yield potential.

Approach:
Objective 1: Exotic maize germplasm from the Germplasm Enhancement of Maize (GEM) Program, the International Maize and Wheat Improvement Center (or CIMMYT), Mexico, and the U.S. maize germplasm collection will be screened for resistance to multiple insects and diseases, and reduced aflatoxin contamination. Equal priority will be given to the GEM and exotic germplasm, since the GEM germplasm will likely have better agronomic traits but the exotic germplasm may have better adaptation to the South. Such a combination has the potential that allows us to identify new germplasm resistant to multiple insects, diseases, and reduced mycotoxin contaminations. To effectively serve the seed industries, the screenings of maize insect pests will focus on ear- and kernel-feeding insects, in particular, stink bugs, sap beetles, thrips and maize weevil. The genetic and biochemical bases for the biotic stress resistance in these newly identified germplasm lines will be further examined. Three genetic studies (i.e., diallel analysis, xenia effect, and heterosis) will be used to elucidate the genetic mechanisms, whereas phytoalexins and other secondary metabolites of plants will be examined to elucidate biochemical and physiological bases of biotic stress resistance. A similar approach is utilized for the screening of sorghum germplasm for resistance to multiple biotic stress factors. Previously identified disease resistant and agronomically-elite germplasm in the U.S. germplasm collection will be screened for resistance to fall armyworm, foliar anthracnose disease, and sorghum midge. The genetic mechanisms of insect and disease resistance will be examined utilizing three genetic studies (i.e., North Carolina Design II, heterosis, and xenia effect). The contributions of the secondary metabolites to biotic stress resistance in sorghum will also be examined. Objective 2: New maize breeding crosses will be made by recombining germplasm with superior agronomic traits with the newly identified germplasm that confers multiple insect and disease resistance and with reduced mycotoxin contamination. New maize germplasm will be developed by continuously screening and continuous self-pollination of the segregating populations. At the same time, recombinant inbred lines (RILs) will also be developed to identify DNA markers for the newly-developed multiple pest-resistant maize germplasm lines. New sorghum breeding crosses will also be made using the newly identified sorghum germplasm lines that are resistant to multiple biotic stresses and with good yield potential. The breeding crosses will be continuously screened and selected, and self-pollinated to develop and release new sorghum germplasm lines (B lines, or maintainer lines). The best B lines will also be converted into A lines (or cytoplasmic-nuclear male sterile lines) to serve the seed industries. At the same time, recombinant inbred lines will also be developed and used to identify DNA markers for the newly-developed multiple biotic stress-resistant sorghum germplasm lines at both vegetative and reproductive growth stages.

Last Modified: 9/10/2014
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