24 
abstentions), and that several questions were raised during the discussion. 
Because of concerns raised at the RAC meeting, approval of the proposed 
field tests was withheld by NIH. 
Dr. Vidaver said the investigators, in their current proposal, addressed 
the issues raised at the October 25, 1982, meeting. She said the investi- 
gators have modified their proposal to test only in one location rather 
than in the six locations proposed in the original request. The investiga- 
tors have also addressed questions of construction, handling, safety, and 
testing and are asking RAC to comment on the choice of antibiotic resistance 
markers . 
Dr. Vidaver thought that the proposed use of bactericides as part of the 
proposed emergency plan could not be recommended. She said burning or 
burying were preferable procedures. 
Dr. Vidaver said the investigators have presented several arguments in 
support of their proposal. These are: 
(1) Fh_ syringae pv syringae and Eh_ herbicola are common and omni- 
present plant epiphytes. Ih_ syringae strains have also been 
widely applied to plants as a biological control agent of certain 
plant diseases. 
(2) Ice nucleation activity, in addition to causing frost damage, 
is considered to be a conditional frost-dependent virulence 
factor in Eh_ syringae pv. syringae . The INA - deletion mutants 
can be consTdered at least partially "debilitated" with respect 
to virulence. 
(3) E. herbicola is not pathogenic on plants (with rare exceptions, 
on crops not grown in California). 
(4) Although certain strains of P. syringae can be pathogenic to 
hosts such as pear, almond, and citrus, disease caused by this 
pathogen on these hosts is rare in California and occurs only 
after predisposition by freezing injury. All P. syringae strains 
used in the experiments will be isolated frcm the surfaces of 
healthy plants, not frcm disease lesions. The use of avirulent 
non-toxin producing strains, in locations where susceptible crops 
are absent, on crops non-susceptible to the bacterium in California's 
climate will protect crop plants of the region. As Eh_ syringae 
is ubiquitous the likelihood of increased disease on either homolo- 
gous or heterologous plants appears remote. 
(5) The habitats of P^ syringae and Eh_ herbicola differ both in 
space and in time although they partially overlap; the epiphytic 
population cycle of Eh_ herbicola during the growing season differs 
from that of P. syringae p.v. syringae . 
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