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In addition, studies on the genomes of 
plant viruses and Agrobacteriun may result in the 
discovery of a mechanism for inserting new genes 
into plants. The current guidelines, established in 
1976, have unnecessarily restricted cloning DNA from 
plants and from plant pathogenic fungi, bacteria, and 
viruses in several ways. First, most permissible 
experiments with DNA from these sources require P2 
or P3 containment. This restriction appears to have 
been based on the unf anil iari ty of NIH with plants 
and their parasites rather than on evidence of 
greater risk involving these organisms. 
Second, there is a prohibition on experiments 
which night increase the virulence and host range of a 
plant pathogen. This in effect rules out complementation 
studies between avirulent mutants. 
Third, there is a requirement that all host- 
vector systems be certified before you can do self-cloning 
experiments or reintroduce DNA which has been cloned 
into E. col i back into its host of origin. This latter 
experiment is, of course, necessary if genes for pathogen- 
icity or nodulation are to be studied, since these properties 
would not be expressed in E. col i . 
Moreover, this requirement for certification of 
hosts creates problems even for the geneticist who is not 
[273] 
