E
Every year farmers in areas which often suffer flood in Southeast Asia lose millions of tons of rice to high water that kills their crops. That large amount of waste may soon be a thing of the past: SUBIA, a gene discovered by researchers which the International Rice Research Insitule (IRRI) and the University of California, allows rice palnts carrying the gene to live completely under water for two weeks.
Flood – resistant(抗水浸) rice turned up among the 110,000 types of seed stored at the institute. It produced disappointingly low yields(产量) , but scientistis were able to transfer the gene into more bountiful varieties. These have shown promising results in tests by growers in India and Bangladesh over the past two years.
This rice success story would not have been possible without the treasure of genetic diversity hidden in the IRRI’s vault (underground room). As the world faces new agricultural challenge – charging climate, bugs and diseases that have developed resistance(抵抗力) to old defenses – such genetic resources are likely to become increasingly valuable. Fortunately, the IRRI is one of more than 1,000 organizations around the world working to protect crop genes. Most plant species grown for food have an associated bank that stores thousands of samples; seeds of landraces, wild relatives, and varieties that are rare, old, or adapted to very specific envionments. The banks ensure that it will be possible to develop new varieties in the future.
The need for these botanical libraries has its roots in modern agricultural practices. According to the U. N. Food and Agriculture Organization, 75 percent of plant diversity has been lost over the last century. Of more than 30,000 eatable species, humans grow just 200 for food; 60 percent of plant calories in our diet comes from wheat, rice, and corn.
72．Accordint to the second paragraph, what can we learn about the flood – resistant rice?
A．It produces a small amount of rice.
B．Scientists have developed many more varieties of it.
C．Sientists have managed to improve its output.
D．It can produce more rice than the other 110,000 types at the institute.
73．From the passage we can infer that        .
A．the newly – discovered gene will bring hope to the farmers in the areas often suffering flood
B．scientists will not be able to change the fact that rice plants carrying the gene produce low yields
C．the tests by growers in India and Bangladesh were hopeless
D．110,000 types of seed stored at the Institute are flood -  resistant
74．What’s the main idea of the third paragraph?
A．The world faces new agricultural challenges.
B．Such genetic resources are likely to become valuable.
C．Scientists set up banks to store thousands of seed samples.
D．We should owe the rice success story to the seed banks.
75．As to the botanical libraries, the writer thinks they are            .
A．useless      B．unnecessary      C．needful     D．needless