2012 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 Germplasm Enhancement of Maize (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.
Approximately 500 entries were advanced in the breeding nursery this summer, and almost 1200 new hybrids were developed for evaluation in 2013. One hundred and sixty entries (of 445 tested) were advanced to second year trials, and twenty-eight entries (of seventy-four tested) were advanced to third year trials. In 2012, over 14,400 yield trial plots were coordinated through Raleigh, with approximately 9,300 of those plots planted at NC State and/or NC Dept. of Agriculture locations and the rest with Germplasm Enhancement of Maize (GEM) cooperators. Approximately 3000 GEM nursery rows and 1200 isolation rows were planted in summer 2012 at Raleigh, and 860 nursery rows were grown in the previous winter in Homestead, FL. Nursery work involved thirty-five different GEM breeding crosses, while ninety other breeding crosses were observed for agronomic traits of interest and 160 were included in yield trials to prioritize further utilization. Disease evaluation continues in 2012 for Gray Leaf Sspot, where advanced materials are evaluated at three locations in North Carolina (Laurel Springs, Andrews and Salisbury). 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; approximately 160 such lines were included in yield trials in 2012 to evaluate agronomic performance.
Over 450 nursery rows in Raleigh 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 35 accessions. The initial steps of the project are coordinated from Raleigh, and the latter steps through Ames, IA; the germplasm produced in Raleigh last summer has been planted by the GEM coordinator in Ames, IA and by GEM cooperators at two locations in Illinois.
Evaluated and recommended semi-exotic germplasm for use by Germplasm Enhancement of Maize (GEM) cooperators. Genetic diversity in United States 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 200-300 recognized races of maize. ARS researchers in Raleigh, N.C. evaluated a large number of semi-exotic breeding crosses (mostly 50% tropical and 50% temperate) and recommended several as promising sources of genetic diversity for breeding programs. ARS researchers in Raleigh, N.C. developed and recommended four 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. Germplasm recommended over the past eight years by the GEM projects in Raleigh and Ames, IA (almost 200 families) was evaluated in head-to-head trials to facilitate the incorporation of GEM germplasm into breeding programs by allowing breeders to select the most promising families.