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1 has given us the key to doing molecular genetics with 
2 these organisms. As a result, this is one of the most 
3 active and promising fields of plant pathology today. 
4 But even so, there are only about a dozen 
5 laboratories in this country involved in this research, 
6 and their efforts are divided among a number of pathogens. 
7 Because manpower here is limited, and because we are working 
8 with genetically uncharacterized bacteria, it is imperative 
9 that we take advantage of the best technology available 
10 today. 
11 Although such studies could possibly be done 
12 by classical genetics, the recombinant DNA technique 
13 offers us a usable means of genetic exchange for organisms 
14 which presently lack one. In addition, it offers the added 
15 advantage that one can now purify the genes for virulence 
16 or host specificity, study the genetic organization, and 
17 characterize their gene products. .The recombinant DNA 
18 approach is faster, less equivocal, and has a greater 
19 chance for success than if the same experiments were done 
20 using classical techniques. Similar experiments have 
21 already proven valuable in the study of animal diseases. 
22 I might add here that the problem of nodulation 
23 by nitrogen-fixing bacteria is very similar to the problem 
24 of host specificity in plant pathogens, and the same rational* 
25 applies to the field of nitrogen fixation. 
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