VOA慢速英语-Agriculture Report - Finding the Biological Roots of

This is the VOA Special English Agriculture Report.
　
A farmer in his maize¹ field near Arusha, Tanzania

The maize streak² virus causes one of the most destructive crop diseases in Africa. Not only is it economically damaging, it can also threaten food security. Maize crop failures lead to hunger in some areas. Maize streak disease also strikes parts of Asia.

Small insects known as leafhoppers carry the virus from field to field. Not much food can come from a field badly infected with the virus. The maize plants cannot produce a healthy cob. The disease gets its name from the streaks³ of yellow and white that discolor the leaves.

There are many less harmful kinds of maize streak virus. These cause minor⁴ infections in crops like sugarcane and wheat. But only one kind causes the most severe form of maize streak disease.

Researchers have been working to understand how this form of the virus got started and spread. They studied eighty versions of maize streak virus. They found that the severe kind may have formed from a recombination of less harmful grass viruses. In the process of recombination, the parent viruses exchanged a gene⁵.

The study compared the genome of the maize streak virus with those of ten related but less harmful viruses. A genome contains all the information about an organism, including information carried from its parent organisms.

The most severe virus may have formed more than a century ago, when two mostly harmless viruses that infect wild grass combined.

Darren Martin of the University of Cape⁶ Town in South Africa led the research. He says the researchers found that every maize streak virus that severely⁷ affects maize came from an ancestral virus. That ancestral virus was the recombinant result of the two comparatively harmless viruses.

But the virus they formed was stronger. It could infect more plants than its parents. It could live through winters in wild grasses better than its relations. The researchers believe that this quality also made the severe form of maize streak virus spread faster.

Scientists from several parts of the world took part in the study, which appeared in the Journal of General Virology. The research continues. The goal is to find more biological information that could help lead to a cure.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. For more reports -- with transcripts⁸, MP3s and podcasts -- go to voaspecialenglish.com. I'm Steve Ember.

 

1 maize   

n.玉米

参考例句：

• There's a field planted with maize behind the house.房子后面有一块玉米地。
• We can grow sorghum or maize on this plot.这块地可以种高粱或玉米。

2 streak   

n.条理，斑纹，倾向，少许，痕迹；v.加条纹，变成条纹，奔驰，快速移动

参考例句：

• The Indians used to streak their faces with paint.印第安人过去常用颜料在脸上涂条纹。
• Why did you streak the tree?你为什么在树上刻条纹？

3 streaks   

n.（与周围有所不同的）条纹( streak的名词复数 )；（通常指不好的）特征（倾向）；（不断经历成功或失败的）一段时期v.快速移动( streak的第三人称单数 )；使布满条纹

参考例句：

• streaks of grey in her hair 她头上的绺绺白发
• Bacon has streaks of fat and streaks of lean. 咸肉中有几层肥的和几层瘦的。 来自《现代英汉综合大词典》

4 minor   

adj.较小(少)的，较次要的；n.辅修学科；vi.辅修

参考例句：

• The young actor was given a minor part in the new play.年轻的男演员在这出新戏里被分派担任一个小角色。
• I gave him a minor share of my wealth.我把小部分财产给了他。

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 cape   

n.海角，岬；披肩，短披风

参考例句：

• I long for a trip to the Cape of Good Hope.我渴望到好望角去旅行。
• She was wearing a cape over her dress.她在外套上披着一件披肩。

7 severely   

adv.严格地；严厉地；非常恶劣地

参考例句：

• He was severely criticized and removed from his post.他受到了严厉的批评并且被撤了职。
• He is severely put down for his careless work.他因工作上的粗心大意而受到了严厉的批评。

8 transcripts   

n.抄本（ transcript的名词复数 ）；转写本；文字本；副本

参考例句：

• Like mRNA, both tRNA and rRNA are transcripts of chromosomal DNA. tRNA及rRNA同mRNA一样，都是染色体DNA的转录产物。 来自辞典例句
• You can't take the transfer students'exam without your transcripts. 没有成绩证明书，你就不能参加转学考试。 来自辞典例句