VOA标准英语2012--Scientists Developing Salt-Tolerant Rice

Scientists Developing Salt-Tolerant Rice

Scientists are developing a salt-resistant variety of rice.
The move was prompted, in part, by last year's Japan tsunami¹, which flooded some 20,000 hectares of rice paddies.
The rice varieties Japanese farmers were growing in those paddies couldn't survive in salt-contaminated soil.
Those ruined paddies might be the first to test out the new rice-growing techniques.
Delicate balance
The challenge before scientists, says plant biologist Sophien Kamoun at the Sainsbury Laboratory in the United Kingdom, is, “How do you introduce a new trait like salt tolerance² into that local variety, while at the same time you maintain all the other traits that make that variety really ideal for that region?”
Plant breeders normally take that ideal variety and mate, or cross, it with one that is salt-tolerant. Some of the offspring would acquire that trait. But they may also differ from the ideal variety in other ways.
“If you make a cross, for example, with an unrelated variety of rice, you will have thousands of differences," Kamoun says.
Those differences may be good or bad. Accentuating³ the positive while eliminating the negative may take a decade or more.
Kamoun and colleagues in Japan started instead with a popular high-quality rice variety and, using a technique common in plant breeding, introduced random⁴ changes - or mutations - in the plant’s genes⁶ with a chemical.
“Then you end up with thousands of plants that have all kinds of changes in their habits," Kamoun says. "And then you plant them out there in the field and identify the plants that have particular traits of interest.”
Sequencing lots of genomes
Then Kamoun’s group did something that would have been too difficult and expensive just a few years ago. They used new technology to sequence the entire genomes of the plants with those traits of interest. They identified precisely⁷ what genetic⁸ changes were found in plants with the new traits and where those changes appear on the map of the rice genome.
It’s a big improvement for crop breeders who usually follow rough landmarks⁹ in the genetic map to guide their efforts.
“Instead of saying, ‘It’s between Street A and Street B,’ you can say, ‘It’s exactly this address,’” says U.S. Department of Agriculture scientist Shannon Pinson.
She was not involved in the research. But she says it is exciting not only because it makes plant breeding more precise. She says even when breeders know where in the genetic map to find the genes responsible for a trait, or phenotype, “That doesn’t mean we know exactly what the gene⁵ is, and what the sequence is and what change in that sequence is causing that change in phenotype.”
Pinson says the new method hones in on the precise changes in a gene responsible for changes in a trait. That should make it easier to figure out how the gene works.
Sophien Kamoun says his colleagues have already improved the salt tolerance of a high-quality rice variety in greenhouse experiments and expect to have it ready for farmers in a couple years - far sooner than conventional breeding would take.
And he says the methods should cut the time needed to develop other varieties and other crops as well.

1 tsunami   

n.海啸

参考例句：

• Powerful quake sparks tsunami warning in Japan.大地震触发了日本的海啸预警。
• Coastlines all around the Indian Ocean inundated by a huge tsunami.大海啸把印度洋沿岸地区都淹没了。

2 tolerance   

n.宽容；容忍，忍受；耐药力；公差

参考例句：

• Tolerance is one of his strengths.宽容是他的一个优点。
• Human beings have limited tolerance of noise.人类对噪音的忍耐力有限。

3 accentuating   

v.重读( accentuate的现在分词 )；使突出；使恶化；加重音符号于

参考例句：

• Elegant interior design accentuating the unique feeling of space. 优雅的室内设计突显了独特的空间感。 来自互联网
• Accentuating the positive is an article of faith here. 强调积极面在这里已变成一种信仰。 来自互联网

4 random   

adj.随机的；任意的；n.偶然的(或随便的)行动

参考例句：

• The list is arranged in a random order.名单排列不分先后。
• On random inspection the meat was found to be bad.经抽查，发现肉变质了。

5 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

6 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

7 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

8 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

9 landmarks   

n.陆标( landmark的名词复数 )；目标；（标志重要阶段的）里程碑 ~ (in sth)；有历史意义的建筑物（或遗址）

参考例句：

• The book stands out as one of the notable landmarks in the progress of modern science. 这部著作是现代科学发展史上著名的里程碑之一。 来自《现代汉英综合大词典》
• The baby was one of the big landmarks in our relationship. 孩子的出世是我们俩关系中的一个重要转折点。 来自辞典例句