Preliminary Results of Transgenic Wheat Trial Look Promising

CIMMYT took a historic step in March 2004 by planting a small trial of genetically engineered wheat in a screenhouse at its headquarters in El Batán, Mexico, following Mexican and CIMMYT biosafety procedures. It was the first time that transgenic wheat has been planted in Mexico under field-like conditions, and encouraging preliminary results have spurred plans for a more extensive follow-up trial.

Striving for Drought- Tolerant Wheat

Researchers at CIMMYT have used genetic engineering to insert a gene from Arabidopsis thaliana, a relative of wild mustard, into wheat. This DREB1A gene, which was provided by the Japan International Research Center for Agricultural Sciences, confers tolerance to drought, low temperatures, and salinity in its natural host. The trial allowed researchers to make a critical step toward developing drought-tolerant wheat varieties by allowing them to see if the DREB1A wheat responds well under field conditions. Drought is one of the most important agricultural production problems in the world. Combined with shortages of groundwater, it threatens the ability of many developing countries to feed themselves. Currently, the 20% of global farmland that is irrigated produces 40% of the world’s food supply.

Encouraging and Consistent Results

Looking at preliminary results after the trial’s end, Pellegrineschi was encouraged by the existence of a
clear phenotype and higher grain yield in the transgenic lines than checks under drought conditions. In
July 2004, the non-DREB control wheat was dry, and yellow, while the DREB wheat was still green and thriving. Pellegrineschi was surprised that one gene could bring about such a visible response.

In this trial, water stress tolerance was always associated with the transgene’s presence. Control plants began to show water stress symptoms, such as turgor loss and leaf bleaching, after 10 days without water. The transgenic lines, on the other hand, started to show water stress symptoms after 15 days.

Pellegrineschi says the results of this trial, which was part of the center ’s collaboration with the Australian Cooperative Research Centre for Molecular Plant Breeding, are compatible with observations from small pots in the biosafety greenhouse. In general, the transgenic lines had relatively higher water content, more biomass, and lower chlorophyll content. They responded better to returning to their unstressed phenotype after irrigation, and they were better able to complete the normal field cycle and produce useful seeds. These results need to be verified in a larger field trial with selected transgenic lines, he says.

Taking Precautions

This is the first time that a food crop carrying the DREB1A gene has advanced to this level of testing. The Mexican government, which had announced a moratorium on planting transgenic plants under field conditions in 1998, approved the trial in December 2003.

The researchers followed strict biosafety procedures and worked closely with the government of Mexico in planning and conducting the trial. Access to the screenhouse was restricted. The researchers covered all plant flowers with bags and did not allow other wheat plants to grow within 10 meters of the trial, even though it is unlikely that selfpollinating wheat plants would cross with each other. After the trial, which was monitored by Mexican authorities and CIMMYT’s biosafety officer, they destroyed all plant materials except harvested seed.

What Next?

“This was the first trial transgenic wheat trial after the government removed the moratorium on growing transgenic varieties under field conditions, so we were very conservative in asking for a large area to the Mexican authorities,” says Pellegrineschi. “Now that we’ve had some success, we’re asking for a larger trial size.” Pending approval from the biosafety committee, researchers are ready to begin a second trial. In response to lessons learned from the first trial, the researchers are going to use a larger plot, have more repetition, and restrict walking inside the plots.

Researchers are also pursuing two strategies to further examine the effects of the DREB1A gene on induction of water stress tolerance in transgenic wheat plants. They are continuing to test the 12 project-selected transgenic lines under field conditions to confirm the observed phenotypes and determine other effects on growth and productivity. They are also introducing additional constructs, which express several DREB genes, into wheat. “With the right investment,” Pellegrineschi says, “researchers will be able to produce drought-tolerant transgenic varieties within five years.”

Meanwhile, CIMMYT researchers plan to combine transgenically-endowed drought tolerance with types of tolerance derived through conventional breeding and from wild grasses, a source of many useful traits with which CIMMYT has worked successfully for more than a decade.

For more information: a.pellegrineschi@cgiar.org

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January, 2005