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April 6, 2001
Drought resistant corn?
It may come sooner than you
think!
By Tim McAlavy
Extension Communications Specialist
A corn breeding project under way at the Texas A&M University Agricultural Research and Extension Center in Lubbock may soon yield drought-hardy, insect-resistant corn hybrids that are equal or superior in yield under limited irrigation to commercial corn hybrids now available to farmers.
The project started in 1980, when Dr. Tom Archer, Texas Agricultural Experiment Station research entomologist and corn breeder, began to identify hybrids with resistance to mites.
For the next 14 years, Archer focused on identifying and breeding hybrids with resistance to mites and corn earworm. From 1995 to 1998, Archer and molecular geneticist Dr. Henry Nguyen selected and bred drought resistant corn hybrids and crossed these with their insect resistant lines. Corn breeder Wenwei Xu joined this team effort in 1998.
That same year the scientists successfully tested full-season corn hybrids bred from this germplasm. These hybrids produced 95 bushels per acre from only 4 inches of rain and 12 inches of supplemental irrigation (5 inches of which was applied prior to tassel), and show good resistance to yield-reducing pests such as mites and corn earworms. In contrast, a drought-resistant commercial hybrid (Pioneer 3223) produced 53 bushels under the same conditions.
"We are making good progress breeding less thirsty, drought-resistant food and field corns, using corn lines bred here for insect resistance," Xu said. "We know that under drought conditions, drought-tolerant plants employ several mechanisms—one of which is short anthesis-silking interval (ASI). Our work centers on transferring the genes responsible for short ASI from tropical germplasm into temperate corn lines bred to perform and yield well under West Texas' sometimes harsh growing conditions. The idea is that corn lines bred to survive and thrive in West Texas will be tough enough to thrive anywhere else in the world."
Selecting and breeding hybrids for insect resistance and drought tolerance is only part of the equation, however. The scientists also are identify ing, selecting and breeding corn hybrids for the "stay green" quality and for heat tolerance to increase stress resistance, Archer said.
Working closely with Drs. Archer, Nguyen and Xu at Lubbock is Dr. Javier Betran, Texas A&M University corn breeder based in College Station. Xu and Nguyen carry out their work under joint appointments from Texas A&M University and Texas Tech University.
The process of transferring superior genes from tropical germplasm into existing temperate corn lines is called "introgression," Xu noted. It isn't easy work.
Crossing tropical and temperate corn germplasm requires hand pollination in the field and greenhouse. Fortunately, the Lubbock center's greenhouses and winter nurseries in Florida enable the researchers to produce two generations of corn lines each year. Crosses of tropical and temperate corn, and their offspring, are then evaluated for drought and insect resistance. Only the best of these plants are selected as breeding candidates.
"Investigating the physiological and genetic mechanisms of corn's drought and heat resistance can be pretty slow work," Xu said. "To speed it up, we are using molecular marker-assisted selection in the breeding process. By using molecular mapping and molecular markers, we can do a better job of identifying and introducing genes that transfer drought resistance traits."
The corn breeding project is partially funded by corn producers contributing to a corn checkoff administered by the Texas Corn Producers Board. Some of the work also falls under the umbrella of the U.S. Department of Agriculture's Germplasm Enhancement of Maize (GEM) project.
GEM is a cooperative effort of USDA's Agricultural Research Service (ARS), land-grant universities and ag industry. It allows scientists to share access to new public and private corn germplasms.
"By diversifying the pool of corn germplasm available to public and private breeders, we can accelerate the process of developing corn hybrids with multiple stress resistance," Xu said. "We are still three to five years away from releasing hybrids based on the lines we developed in 1998. But they are a start in fulfilling the farmer's need for productive, early-season corns that require less water and withstand insect damage."
