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Severe drought in the US:

“There are no magical plants”

The heatwave that has been stifling large parts of the US for weeks is continuing. Nearly two-thirds of the country is affected by the drought, which is causing serious harvest losses, particularly in the Corn Belt, the huge maize-growing region of the Midwest. The UN fears a new food crisis. Long before this latest crisis, plant breeders and researchers had started trying to develop drought-tolerant plants. Conventional maize varieties bred using modern molecular biological methods, which cope better with heat and need less water, are already being grown on around 800,000 hectares in the US. A genetically modified drought-tolerant maize variety was approved in 2011 and is due to be brought onto the market in 2013.

US President Barack Obama and Secretary of Agriculture Tom Vilsack visiting a drought-affected farm in Iowa in mid-August
Photo: USDA

Stunted maize cobs. A consequence of the summer 2003 heat wave. The male flowers sent forth pollen before the female flowers had formed their silks.

Maize cannot develop during long periods of heat and drought. It produces meagre cobs and the maize straw dries out. The current drought will show whether the new drought-tolerant maize varieties cope better with heat stress and water shortages than other varieties.

Following the hottest July since records began more than 100 years ago, Financial Times Deutschland reported that the US Department of Agriculture (USDA) had been forced to cut its harvest forecasts on 10 August. The maize harvest is expected to be around a sixth lower than last year, and up to a third lower in the Corn Belt. The estimated harvest loss for cereals as a whole is 13 per cent, and 12 per cent for soya.

The US is the world’s largest agricultural exporter and accounts for almost half of global maize exports. The American harvest therefore has a big impact on global markets. According to Spiegel Online, prices for soya have risen by around 30 per cent since the start of the heatwave in June, while maize prices have risen by around 50 per cent. Handelsblatt reports that food prices went up by six per cent in July, according to UN calculations. This has a particularly significant impact on the world’s poorer food-importing nations. Here, staple foods are becoming unaffordable and the UN fears there will be another food crisis like those of 2008 and 2010.

On 8 August, the Food and Agriculture Organization of the United Nations (FAO) called on the US to restrict biofuel crops because food production must take priority. Since 2007, there have been quotas in the US for bioethanol levels in fuel. The regulations are designed to increase the proportion of renewable energy sources in the fuel mix. In 2012, these environmental restrictions on fuel will require more than 50 billion litres of bioethanol, much of which is produced from maize. Forty per cent of the maize grown in the US is used for the production of green fuel.

New drought-tolerant maize varieties put to the test

Plant breeders and researchers all over the world have been working for a long time to develop plants that are better able to cope with drought and other stress factors. Since drought tolerance, for instance, is not controlled by individual genes, a lot more basic research is required to understand the many biological processes and mechanisms that enable plants to deal better with heat and with water shortages.

Monsanto and BASF have jointly developed a drought-tolerant GM maize variety with the brand name DroughtGard, which is due out in 2013. The maize contains a gene from a bacterium, Bacillus subtilis, which causes the plant to produce a protein that helps important cell functions carry on working in the event of water shortages and drought. According to information provided by the companies, the yields for this maize were six to ten per cent higher than for conventional maize plants at the same site when exposed to “moderate drought” without additional irrigation. Trials conducted by the USDA, however, produced yields that were only around three per cent higher. DroughtGard was approved in 2011 and is being tested this year by 250 farmers in five states on a total area of around 40,000 hectares.

Conventionally bred drought-tolerant maize varieties from Pioneer Dupont, are already on the market and produced similar results in field trials. Last year these varieties, called Aquamax, were tested on 8000 farms and they are being grown on around 800,000 hectares in 2012. Aquamax was developed with the help of new molecular biological methods, including smart breeding.

However, even the new drought-tolerant maize varieties are not completely immune to extreme temperatures like those still affecting large parts of the country. “We know there’s a limit; we know you cannot grow corn without water,” Jeff Schussler, senior research manager in maize stress product development for Dupont Pioneer, told Scientific America. “There’s nothing magical about these hybrids.”

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