JOHANNESBURG

As temperatures soar and droughts increase in frequency, scientists around the world are working to create food crops tolerant of extreme temperatures - often an expensive and laborious process. But a cheaper and quicker alternative could be in sight, new research suggests.

Fungi and other microbes could enable food crops like maize, wheat and rice to grow in high temperatures and salty soils, and even withstand erratic rainfall, say microbiologists, who have begun to look at the relationship between plants and micro-organisms for clues to their mutual survival through thousands of years of climate change.

Making food crops tolerant to climatic stresses could be as simple as coating seeds with micro-organisms that can confer desired traits.

A matter of urgency

Helping food crops weather climate change is a matter of urgency, said experts from 15 research centres of the Consultative Group on International Agricultural Research’s (CGIAR) Research Programme on Climate Change, Agriculture and Food Security. The programme had been asked by the UN to summarize the effects of climate change on 22 of the most important agriculture crops, from staple cereals to potatoes, lentils and commercial fruit crops like bananas.

Time is of the essence, as droughts have already become more frequent and rainfall more erratic in various parts of the world. By 2050, climate change could cause irrigated wheat yields in developing countries to fall by 13 percent, says a CGIAR review by senior scientist Philip Thornton. Irrigated rice yield could fall by as much as 15 percent. In Africa, many farmers of maize could lose 10 to 20 percent of their yields.

We have always thought that plants had learned to adapt to climatic stresses like high temperatures and drought, but now we find that microbiomes [communities of microbes] within plants have conferred traits on them to be able to withstand the stress

Some temperature-tolerant new crops are already being grown in Asia, developed by subjecting grain plants to stresses such as drought conditions, then isolating genes from those that survive. But this kind of conventional breeding is long-drawn process, often taking 10 to 15 years to develop a successful crop variant. It is widely used because many Asian and African countries do not accept genetically modified (GM) products.

Micro-organisms could provide a faster option.

Microbiomes aid survival



"We have always thought that plants had learned to adapt to climatic stresses like high temperatures and drought, but now we find that microbiomes [communities of microbes] within plants have conferred traits on them to be able to withstand the stress," said Rusty Rodriguez, a microbiologist affiliated with the University of Washington, who recently established his own non-profit organization (Symbiogenics) to conduct more research into the plant-microbe symbiosis.

Human and plant life is intertwined with that of micro-organisms. A human body contains more bacteria than human cells; in several studies published this year, members of the Human Microbiome Project reported that microbes "contribute more genes responsible for human survival" than humans themselves.

The new plant studies show that microbiomes are similarly crucial in the plant world.

Scientific American reported in 2010 that Mary Lucero, a molecular biologist at the US Department of Agriculture, had found fungi could help plants capture more nitrogen from the atmosphere, reducing the need to apply chemical fertilizers.

More recently, Rodriguez and his team have shown how a certain fungus, when introduced to the seeds of maize, wheat, tomatoes, watermelons and other plants, enabled those plants to withstand more than 50-degree Celsius temperatures.

‘Results within a year’



Rodriguez says he took fungi from plants near the hot springs in the US’s Yellowstone National Park. The stress tolerance traits are only found in microbes found in those conditions; the same fungus isolated from a non-stressed condition do not have those traits. His teams have also undertaken missions to collect fungi from extreme conditions in the Antarctic, Mount Everest in the Himalayas and the Great Basin Desert in the US.

Rodriguez said he and his team could likely find similar microbes in any part of the world - for instance, in the Sahel - and conduct trials within the region to isolate the useful microbes. "We could have results within a year," he said.

He has already conducted trials in the US with maize and rice, and found that yields can grow up to 10 percent in the case of rice in cold temperatures, and up to 80 percent in the case of maize in high temperatures. The team is awaiting the results of a trial in which maize was grown during the worst drought to hit the US in decades.

He has also isolated a virus in the fungus that makes plants even more resilient to heat.

The plan is to keep the costs of providing the technology to farmers very low. "Corn in the US is sold in 42lbs [about 20 kg] bags. We want to keep the cost of coating the seeds with microbes to under US$20 [per bag]," said Rodriguez

Another peer-reviewed study has shown that certain fungi can make rice plants more tolerant to drought, salt and even cold while reducing water consumption by 20 to 30 percent. Salt tolerance is a sought-after trait in regions affected by rising sea-levels and storm surges that cause saltwater intrusion, such as the rice-growing regions of Bangladesh and Vietnam.

Research for developing world



Rodriguez said he and others are looking for opportunities and funding to conduct trials in Africa, where this technology is desperately needed.

This point was also made by CGIAR’s Thornton in his paper Recalibrating Food Production in the Developing World: Global Warming Will Change More Than Just the Climate, which explores the complexities of climate change’s impact on crops. Some crops might be able to withstand high temperature but could be sensitive to changes in rainfall. "Other crops can tolerate seasonal flooding but are susceptible to new or increased levels of pests and diseases brought on by high temperatures."

A variety of changes must take place, including changes to the mix of crops being grown, Thornton said in an email to IRIN. Research can help by "showing farmers not only how to grow new crops but also how to utilize them in different ways (e.g., different ways of preparing and cooking cassava). The socio-cultural aspects may be difficult to deal with, but through a combination of market forces (changes in relative prices of staples) and time, diets may change slowly,” he said.

Circumventing controversy?



Meanwhile, other researchers are exploring the use of GM to increase crop resilience. But the safety of GM has been heatedly debated, with many activist groups, governments and regulatory bodies calling for products containing GM ingredients to carry special labels.

The American Association for the Advancement of Science has recently come out against labelling requirements. “These efforts are not driven by evidence that GM foods are actually dangerous. Indeed, the science is quite clear: crop improvement by the modern molecular techniques of biotechnology is safe.”

The microbiome studies might offer a way to circumvent these controversies, offering faster and cheaper solutions without the patina of “mad science” often attributed to GM products. The journal New Scientist reported this year that, unlike genetic engineering, which takes years to induce plants to switch various metabolic pathways to become more drought-tolerant, fungi can activate "them all in one go."

jk/rz