Tab A - Page 27 
(a) greenhouse Instead of field conditions with prolonged moisture, 
non-fluctuating temperature, protection from UV light, etc.; 
(b) heavy Inoculum (typically 10^-10^, often 10^-10^ cfu/ml), 
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unrepresentati ve of natural levels (maximally 10 -10 cfu/ml in rain water); 
(c) artificial methods of inoculum delivery (e.g. stabbing stems or twigs 
or leaves with heavily inoculated needles or injecting bacterial suspensions 
with hypodermic needles), which bypass epidermal, bark or other structural 
barriers to infection. 
At high inoculum concentration, pathogenicity can be easily confused with 
the hypersensi ti ve reaction (HR), a common resistance response of plants to 
heterologous pathogens (i.e., strains which infect host(s) other than the one 
being tested). HR, which was not known as such prior to the mid-60's, occurs 
with most bacterial and fungal plant pathogens on their non-host plants and, 
when the infected inoculum concentration is 5x10^ to 10^ cfu/ml or greater, is 
visible to the naked eye as localized necrosis and senescence of the inoculated 
tissue. Adding to the above confusion are several cases of misidentlflcation. 
Bacteriological -nutri tional tests that distinguish £. _s* syrinaae from other 
closely related plant pathogenic bacteria currently classified as "pathovars" 
of the £. syri noae group were inadequate or unavailable in the past. Although 
this situation has improved considerably in recent years, the key tests are not 
routinely employed by workers who are not expressly interested in taxonomy or 
host specificity. 
/■ 
In summary, some strains of P_. s_. syrinqae have a quite narrow host range 
and show a striking correlation between pathogenicity and host of origin, while 
other strains appear to have a broader host range, the limits of which are 
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-y M i ~ i v a r ivf 
