This is the VOA Special English Agriculture Report.

Soybeans are eaten by people and fed to animals. Some farmers grow them to replace lost nitrogen in the soil.

Soybeans were first grown in Asia thousands of years ago. Now scientists have a full genetic map of the soybean. This is the first genome completed for a member of the legume family.

The genome will make it easier to target different qualities and develop improved crops. Sequencing the genes, organizing all of them in order, will save many hours of searching. It will make it easier to search for what each gene is responsible for.

A report on the genome appeared last week in the journal Nature.

Scott Jackson at Purdue University in West Lafayette, Indiana, helped lead the study team. He says the kind of soybeans they studied have 46,000 genes. Between 70 and 80 percent of them, however, are copies of other genes.

Some genes change or disappear over time. But Professor Jackson explains that soybeans have kept copies of most their genes. This is fairly unusual for plants, he says, and extremely unusual for animals.

Genes are organized along chromosomes. These contain molecules of DNA, the building blocks of life.

The researchers found that the sets of chromosomes in soybeans have copied themselves at least twice. It happened almost 60 million years ago and again 13 million years ago.

Over time, genes develop changes, known as mutations. Scientists can tell when these changes happened. The number of mutations over time helped the team estimate when the duplications in soybeans took place.

The genome could help genetic engineers develop soybeans that are processed better by farm animals. Soybeans contain chemicals called phytates. These prevent the absorption of phosphorus in the diet.

Pigs and chickens especially are affected. Undigested phosphorus in their waste can pollute water supplies.

Genetic engineering has already reduced phytates in soybeans. Now with the gene map there could be further reductions.

The genome could also help farmers avoid Asian soybean rust disease, a highly destructive fungus spread by the wind. The researchers say they found a gene for resistance to this disease. Now they have to find a way to use it.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. You can find transcripts, MP3s and captioned videos of our reports at voaspecialenglish.com. I'm Bob Doughty.

legume: any plant that has seeds in long pods. Peas and beans are legumes 豆科作物

chromosome: one of the very small parts like threads in the nuclei(= central parts) of animal and plant cells, that carry the genes 染色体

phytate: 植酸盐

phosphorus: a chemical element found in several different forms, including as a poisonous, pale yellow substance that shines in the dark and starts to burn as soon as it is placed in air 磷

Related stories:

New understanding of how plants use water

Keeping plants and trees warm when temperatures drop

New alliance to study greenhouse gases in agriculture

Solar-powered pumps aid African farmers

(来源：VOA 编辑：陈丹妮）