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United States Department of Agriculture

Agricultural Research Service

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Location: Plant Science Research

2010 Annual Report

1a. Objectives (from AD-416)
The long term objective of this project is to diversify the genetic base of maize in the United States by the addition of new genes from exotic maize that will improve agronomic productivity, disease resistance, and insect resistance, and contribute value-added grain characteristics, including total extractable starch to support ethanol production.

1b. Approach (from AD-416)
Manage GEM field nurseries, seed inventories, and germplasm exchange so that new sources of germplasm and information reach stakeholders annually. With the GEM Project Technical Steering Group (TSG), identify and acquire new sources of exotic maize germplasm for breeding and diversity assessment projects. Conduct cooperative maize germplasm evaluations for host-plant resistance to gray leaf spot, southern corn leaf blight, northern leaf blight, and fumonisin production. Develop advanced maize breeding families, derived from non-U.S. and U.S. sources which are selected for wide adaptation to U.S. conditions.

3. Progress Report
In the Germplasm Enhancement of Maize (GEM) project, Ninety-four entries (of 425 tested) have been advanced in the summer nursery based on early generation trials in 2009, and 47 entries (of 175 tested) were advanced from first-year advanced-generation trials to second-year advanced-generation trials. In 2010, over 12,000 plots were coordinated through Raleigh, with approximately half of those plots planted at NC State and/or NC Dept. of Agriculture locations, and the other half with GEM cooperators. Approximately 3200 GEM nursery rows and almost 1000 isolation rows were planted in 2010 at Raleigh, and almost 800 nursery rows were grown in the winter in Homestead, FL. Nursery work involves nine new GEM breeding crosses. In 2009, the effort to evaluate GEM breeding crosses for yield per se was continued as part of the evaluations of new germplasm. Data from these studies continue to reveal a great spread in yield potential, and those results influenced our choices for 2010 nursery work. The per se yield trial evaluations were discontinued in 2010 in favor of testcrossing the breeding crosses to determine their performance in hybrid combinations using GEM testers. The rationale behind this change is that breeding crosses that perform well with GEM testers are more likely to produce maize families that perform well with GEM testers, and that our resources should be focused on those breeding crosses. Disease evaluation continues in 2010 for Gray leaf spot, where advanced materials are evaluated at three locations in North Carolina. Also, we have continued routine screening of available tropical inbred lines, as so little data are available to choose among them for use in GEM or other research. Over 600 nursery rows in Raleigh (and an additional 100 rows in Columbia, MO.) are devoted to further increasing the genetic diversity in maize through identification of useful alleles in exotic germplasm, which involves accessions that are outside the core plant breeding materials utilized by GEM and most plant breeding organizations. These accessions may contain valuable alleles of interest to breeders that would otherwise not be utilized due to the difficulties in growing tropical germplasm per se in the Corn Belt. The new crosses represent about 50 accessions. The initial steps of the project are coordinated from Raleigh, and the latter steps through Ames, IA. The crosses were produced last winter in Hawaii and in Puerto Rico by GEM cooperators using two off-patent maize inbreds. Backcrosses to the two off-patent maize inbreds were made this summer in Raleigh (and in Columbia, MO), while the germplasm produced in Raleigh last summer has been planted by GEM coordinator in Ames, IA and by GEM cooperators at two locations in Illinois.

4. Accomplishments
1. Promote increased genetic diversity in U.S. maize breeding programs. Genetic diversity in U.S. maize breeding programs is limited by use of a very limited base of maize germplasm that is derived primarily from the race “Corn Belt Dent”, only one of the approximately 300 races of maize. ARS researchers in Raleigh, N.C. developed and recommended ten germplasm lines to the GEM cooperators for use in their breeding programs. These germplasm lines were derived from exotic sources and have acceptable yield and improved disease resistance as compared with standard commercial varieties.

Last Modified: 07/23/2017
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