Plant pathologistshave made remarkable strides in identifying the patho-gensof the various diseases. Bacteriamay invade a plant through an infes-tationof insect parasitescarrying the pathogen. A plant can also be inoc-ulatedby man. Other diseases might be caused by funguswhich attacks the plant in the form of a moldor smutor rust. Frequently such a primary infection will weaken the plant so, that a secondary infection may result from its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by a primary virus infection.
36. How many diseases are known to attack wheat?
A. Around 30,000
B. Around 140
C. Around 29,960
D. Around 40
37. According to this passage, which of the following would a plant disease result in if it was left unchecked?
A. A world war.
B. Border conflicts
C. Rations of grain and meat.
D. Social upheavals.
38. What is the main idea of the second paragraph?
A. Some plants have relative immunity to a great many diseases, while others have a susceptibility to them.
B. The tolerance of a particular plant changes as the growing conditions change.
C. A blight killed virtually every chestnut tree in North American.
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