Line Development
The maize breeding program at North Carolina State University is committed to the development
and release of improved maize inbred lines that show superior agronomic performance and yield potential. Breeding efforts focus
on three heterotic groups: Stiff-Stalks, non-Stiff-Stalks, and Tropical-Exotics (Fig 1). Since Dr. Don Thompson's tenure in the program to date,
157 inbreds have been developed and released. 90 of these inbreds are all or partially-tropical in origin. NC State provides an
ideal environment for a long-term breeding program with tropical maize given its southern location and its historical emphasis on maize
breeding. This program represents an important resource for maize improvement and diversity in the U.S. For information on individual lines
and to request germplasm visit Germplasm.
The NC State maize breeding program places emphasis in the following areas:
1. Superior yield potential
2. Incorporation of novel germplasm
3. Earlier maturities
4. Disease resistance
1) Yield Potential
NC State has released numerous lines that rival or beat commercial hybrids in topcross yield trials. In a two year yield trial across 8 North Carolina environments
NC368 x NC320 out performed the commercial checks by a healthy margin (Table 1).
2) Novel Germplasm
The maize breeding program at North Carolina State University has been breeding with tropical germplasm for nearly 25 years. NC State provides an ideal environment for a long-term breeding program with tropical maize given its southern location and its historical emphasis on maize breeding. To date, over 65 NC lines have been released that are of partial or all-tropical origin.
3) Earlier Maturities
Because of the threat of hurricanes in North Carolina, there is new emphasis on earlier maturing hybrids. Many once-popular, full-season hybrids are no longer being produced, although some are still being sold from reserves. The NC State maize breeding program is conducting an extensive backcross program to early up many if its later lines.
4) Disease Resistance
Several diseases impact corn production in North Carolina: southern leaf blight, gray leaf spot, fusarium, diplodia, southern rust, and anthracnose. Line development at NC State incorporates rigorous screening for a broad spectrum of these and other diseases. NC State's gray leaf spot screening program is very extensive, testing at three North Carolina mountain locations. The incorporation of exotic germplasm not only introduces novel alleles for disease resistance but also superior yield potential.
The NC State maize breeding program grows about 8,000 and 20,000 nursery and yield trial plots, respectively, on an annual basis. Our summer breeding nursery is located at Central Crops Research Station in Clayton, NC.
Our winter nursery is located at 27 Farms in Homestead, FL. Yield trials are conducted at 5 central and eastern North Carolina Locations, Central Crops Research Station in Clayton, NC, the Peanut Belt Research
Station in Lewiston / Woodville, NC, the Tidewater Research Station in Plymouth, NC, the Sandhills Research Station in Jackson Springs, NC, and the Caswell Research Station in Kinston, NC. In addition to
nursery and yield trials, about 3,000 plots are grown in gray leaf spot trials in three mountainous North Carolina Locations, Andrews, NC, Laurel Springs, NC, and Salisbury, NC (Fig 2, Fig 3).
Breeding strategies are focused primarily on improving yield, disease resistance. Topcross yield trial testing is generally practiced at the S3 or S4 stage of inbreeding. Early-generation yield trial testing is generally not practiced due to space limitations. Population sizes range from <10 to >50 F2-derived families, depending on the type of material being tested.
Figures 2 and 3 courtesy of Dr. N.O. Nelson, Department of Agronomy, Kansas State University.
