5.4.7.1 
Wildfire, caused by Pseudomonas syringae pv. tabaci, 
may be particularly damaging in seed beds and 
following storms in field tobacco. One Havana Seed 
variety (Havana 503) was released to growers a number 
of years ago (24) as being resistant to this disease. 
Subsequently, a second race (race 1) of the bacterium 
appeared that was pathogenic to Havana 503. A new 
variety of tobacco, resistant to both races of P. s. pv. 
tabaci, is in the process of being released. This 
resistance is the result of transfer of genetic material 
from N. rustica to N. tabacum (25). 
5.4.7 .2 Blackfire, caused by P_. s. pv. angulatum, may damage 
field grown tobacco. The causal organism is closely 
related to P. s. pv. tabaci and varieties resistant to 
one organism are resistant to the other (9). Havana 
425 and the experimental tobacco to be field tested 
are susceptible to both these bacterial diseases. 
5.4 .S Alterations in Susceptibility to Virus Attack 
A number of virus diseases occur in tobacco in Wisconsin. There 
is no reason to believe that the genetic changes introduced into 
the tobacco in the test plot should affect susceptibility to viral 
diseases. Any changes should be confined to the test plot. 
Environmental Assessment 
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