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The fight to save the banana just gets more challenging．A fungus(真菌)that threatens the world’s most popular fruit is spreading．And it's doing so despite huge efforts to stop it．
The killer fungus is known as Tropical Race 4，or TR4 for short．It’s the fourth type of fungus to cause Panama disease that destroys the roots of banana plants and stops them from growing.TR4 wipes out banana crops wherever it reached the Philippines and southern Africa．
For their new study，Gert Kema，a professor from Harvard University，and his team examined fungus from each of these locations．The researchers analyzed TR4 DNA from bananas in those countries．If the genes in some bananas were quite different from those in others of their type，some banana plants might be able to resist the fungus．
Unfortunately，no cure for banana plants infected with TR4 exists．Because the fungus releases spores(孢子)into the soil，these tough，seed—like structures wait until another banana is planted nearby．Then they attack it．That means a farm that has been infected will stay infected．And live spores can hang on in the soil for decades，waiting for their next victim．What’s more，irrigation water and equipment can spread the disease．Even dirt on the shoes can send spores from one spot to another．All of these help to explain how TR4 has been spreading since its original outbreak．
Kema’s team identified the TR4 clones through a DNA-sequencing technique．It allows rapid identification of an organism’s(微生物)genes．”Farmers can also use a different type of DNA test to check their soil．Doing so could help to slow the spread of TR4．”Kema notes．The hope is that over time researchers may be able to develop bananas that are resistant to fungus．
33．What is the passage mainly about?
A．The killer of bananas worldwide． B．The result of the new study．
C．The cure for banana plants． D．The way a spore is reproduced．
34．What’s the character of TR4?
A．It mainly lives in water．
B．It is the deadliest disease for plants．
C．It can carry spores in banana fruits．
D．It is easily spread in various ways．
35．We can know from the passage that______．
A．banana plants can be saved by genes
B．a spore only exists in the soil for several years
C．there is no efficient way to fight TR4 at present
D．it’s easy to find a cure for plants infected with TR4
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