VOA常速英语:Agricultural Research Aims to Improve Harvests on Warmer Planet

Climate change has brought dramatic droughts and floods around the world, ruining harvests of important cereal crops and reviving concerns about food security on a warmer planet. Researchers at the U.S. Department of Agriculture are looking at cereal crops at risk and their wild, weedy relatives.  The weeds are more resilient under extreme conditions, and seem to be benefiting from climate change, while regular crops suffer.

Plant physiologist Lewis Ziska has been comparing cultivated rice and a weedy red rice relative for several years. The USDA researcher is growing each variety under different temperatures and levels of carbon dioxide. So far, the red rice has flourished under warmer temperatures. It grew faster and produced more seed than the cultivated variety.

"What we have been doing is looking at weedy rice as a unique source of genes that would allow cultivated rice to begin to adapt to still be able to produce very good yields with changes in temperature," said  Ziska.

These environmental growth chambers allow scientists to control heat, humidity and CO2 levels.

"Using these kinds of growth chambers allows us to dial in carbon dioxide concentrations that existed 50 years ago, it allows us to simulate a condition 50 years from now,"  Ziska  added.

Chamber two simulates today's conditions.  The rice in the center and on the left is regular crop rice. The variety on the right is the weed, already blossoming.

In chamber three, Ziska says, the CO2 level is higher and the temperature is two degrees warmer than today.

"This is normal rice, that I just pick from here," Ziska explained.  "It is a panicle for normal rice, you can see is just starting to flower and starting to produce the seed. Here is the same panicle, everything has been equal, but this is now for the weedy rice. And you can see for the weedy rice how much further along it is."

And chamber four, four degrees warmer than today, replicates the conditions that scientists say the world could experience in 30 to 50 years. Again the weedy rice did better, but the regular rice had a dramatic decline.

"It tends to become sterile," noted  Ziska.  "The flower, the pollen becomes sterile at higher temperatures and as a result of that, the plant may look OK, but you are not going to get any rice seed out of it."

Ziska notes that regular rice cannot tolerate the wide range of climate conditions that red rice, as an adaptable weed, can. What is more important, he says, is that most cereals have a weedy relative.

"What we are doing is what nature does: we are selecting for the best set of genes, but in this case the best set of genes that would respond to a wide set of circumstances, instead of a very narrow set of circumstances," Ziska explained.

According to the Department of Agriculture, Thailand, Vietnam, China and the United States are the world's leading rice producers with four main types of rice traded globally.  Ziska says many people around the world depend on rice for their food and livelihoods.  "Anywhere from two to three billion people," Ziska added.  "It is the principle, most important cereal in the world."

Scientist Lewis Ziska hopes to produce a weedy rice seed that can be offered to farmers within the next 3 to 5 years. He still needs to study the red rice under extreme drought and flooding conditions. He believes in a few decades, it could feed a world facing uncertain and extreme climate conditions.