There are several thousand varieties of tobacco. Havana 42 5, the variety 
to be field tested, was introduced in 1955 by a University of Wisconsin 
plant pathologist because of its resistance to the tobacco mosaic virus and 
black root rot. However, Havana 425 is seldom grown today. Havana 425 
was replaced by other varieties which had similar or better yields, 
improved disease resistance and lacked this variety's susceptibility to wind 
damage. 
Agracetus chose Havana 425 for laboratory research because it is well 
suited to recombinant experimental use and one can easily obtain callus 
growths. 
Tobacco has been grown in Wisconsin for well over a hundred years with no 
known adverse ecological effects. The size of the crop varies from. year to 
year depending on the market price and allotment quotas. Experimental 
tobacco is exempt from allotment restrictions as long as it is not 
marketed. In 1983, Dane County, Wisconsin harvested 3,080 acres of 
tobacco, mostly in the southern and eastern parts of the county. The 
proposed plot is an insignificant addition to the total tobacco grown. 
Most of the tobacco grown in Wisconsin at this time contains genetic 
fragments of other Nicotiana species, introduced by more conventional 
means to provide resistance to diseases. For example, a small chromosome 
segment, essentially a single gene, transferred from N. glutinosa (12) 
conditions a hypersensitive response to tobacco mosaic virus. This response 
localizes the virus near the point of infection and effectively eliminates 
spread of the virus within the plant and between plants. Over 90 percent of 
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