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Corn+Soybean Digest

Thirsting For Drought-Tolerant Corn

All the $5 corn in the world doesn't matter if Mother Nature unleashes a devastating drought that can turn many a promising crop into a parched wasteland.

From the southern roasting in Georgia and elsewhere in 2007 to South and West Texas this year, drought strikes anywhere and everywhere at one time or another. While heavy spring rains can slow planting, summer drought can suck up soil moisture during peak pollination periods.

Add to that the threat of aflatoxin in many southern growing areas hit with heat and humidity that triggers the fungus, and it's a real problem for growers.

But seed companies are making progress in both conventional and biotech material for growers, says Wenwei Xu, corn breeder for Texas A&M University in Lubbock.

“Monsanto, Pioneer Hi-Bred, Syngenta and others are working on drought-tolerant hybrids,” says Xu, who develops drought-tolerant lines for use by commercial seed companies. “We expect to see more in the future. At least 10 companies have requested and obtained the seeds of the drought-tolerant germplasm we have developed.”

More than 40 corn varieties listed in “Hotshot Hybrids” ( hybrids-decisions/index.html, Corn & Soybean Digest, November 2007) boasted some degree of drought tolerance.

Xu says yields of the latest lines are comparable to commercial hybrids on the market.

Under irrigation, the drought-tolerant lines can yield even if water is cut back. For example, Xu's Texas A&M research shows that some drought-tolerant hybrids receiving irrigation equal to 75% of evapotranspiration (ET) — the amount of water the plant uses in a 24-hour period — can yield the same as less drought-tolerant hybrids watered at 100% ET.

“Under drought stress, the lines withstand the heat and have better quality grain,” Xu says. “Since there is less stress, the lines are less susceptible to aflatoxin.”

AFLATOXIN CAN TURN a bumper corn crop into a bin of grain toxic to humans or animals. Up to 200 parts per billion (ppb) aflatoxin is the limit for livestock feed. It's 20 ppb for human consumption. “Some countries even want less than 2 ppb,” says Steven Moore, Louisiana State University corn and soybean breeder at Alexandria.

He says research on drought tolerance and aflatoxin resistance tie together. “There is an overlap, because aflatoxin usually happens when corn plants are under stress from heat and humidity across the South,” says Moore.

He is working with potential resistance to aflatoxin developed by Don White, an active professor emeritus at the University of Illinois. About 30 hybrids have been planted at Alexandria for performance testing this year.

In other research, Moore has been working with corn lines obtained from the North Central Regional Plant Introduction Station at Ames, IA. The lines are crossed to produce hybrids and then tested in screening trials.

He has selected about 40 lines that have recorded comparatively low aflatoxin in initial screening trials. The lines have now been hybridized with a common parent and were evaluated for aflatoxin resistance this summer. “We're hopeful that we find resistance that is superior to what we have now,” says Moore.

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