Ch. 7— Maintaining Plant Diversity Offsite • 189 



DNA. DNA is "cut" enzymatically (using re- 

 striction endonuclease enzymes) into pieces or 

 restriction fragments that can be separated on 

 electrophoretic gels. Because RFLPs represent 

 the whole genetic composition of the sample, 

 comparing individual analyses within a sam- 

 ple or among accessions would indicate the 

 variability that exists. The techniques, however, 

 are expensive and require technical expertise 

 to execute and interpret. Thus, use of RFLPs 

 appears limited at present to appropriately 

 equipped laboratories (114). RFLPs have been 

 useful in developing detailed genetic maps for 

 use in breeding programs (48) but are not rou- 

 tinely applied to characterization of germplasm. 



Phytochemical Analysis.— Phytochemical 

 analysis deals with the distribution and chemis- 

 try of organic compounds synthesized by plants 

 (114). 



Analysis involves three general processes: ex- 

 traction, isolation, and identification (44,114). 

 Plant materials are homogenized in aqueous 

 alcohol, then purified by evaporation of the al- 

 cohol and chemical partitioning to remove con- 

 taminating substances and isolate the chemi- 

 cals of interest (114). Chemicals can then be 

 identified by chromatographic or spectroscopic 

 techniques (114). 



During the past 10 years, the major techno- 

 logical advance in separation and purification 

 of organic chemical mixtures has been the de- 

 velopment of high-performance liquid chro- 

 matography (HPLC). HPLC is more rapid than 

 other chromatographic procedures and can iso- 

 late a range of plant chemicals. Developing 

 appropriate HPLC procedures, however, re- 

 quires considerable investment of funds and 

 time. Some facilities of NPGS, however, are 

 using techniques such as HPLC to help char- 

 acterize germplasm (19). 



Recent advances in microcomputers have 

 provided sophisticated, low-cost spectropho- 

 tometers that can identify plant chemicals (114). 

 Other techniques, such as nuclear magnetic res- 

 onance spectroscopy and mass spectrometry, 

 also can determine chemical structure but they 

 require considerable technical expertise and ex- 



pensive instrumentation. These technologies 

 have been used extensively, however, by sci- 

 entists studying the taxonomy and systematics 

 of plants (114) and by university and industry 

 scientists interested in developing potential 

 uses for wild plants in medicine and industry. 



Controlling Pests and Pathogens 

 in Collections 



Managing stored samples requires efforts to 

 ensure that seeds or plants are not lost to pests 

 or pathogens. Because a collection may distrib- 

 ute seeds to other regions, precautions must 

 be taken to reduce the possibility of sending 

 pests or pathogens as well (61). 



Stored seed can be severely damaged by ro- 

 dents, insects, or fungus (58). With rodents, the 

 major damage is not from consumption but 

 rather from the pests scattering and mixing up 

 different accessions (58). Many insect, fungal, 

 and bacterial contaminants can be controlled 

 with the use of chemical fumigants, although 

 such treatments might also harm the seeds (58, 

 59,81). Sanitary storage facilities that obviate 

 the need for such treatment are therefore prefer- 

 able (81). When dried seeds are kept at subfreez- 

 ing temperatures, the potential risk is minimal 

 (58,101). 



The risk of disseminating pathogens is con- 

 siderably greater for crops maintained through 

 clonal propagation (59,61). Some facilities with 

 a specific focus may have greater expertise with 

 a crop and its diseases than a national quaran- 

 tine facility concerned with all potential intro- 

 ductions. Cooperation between scientists and 

 quarantine officials can improve control of 

 pathogens and aid technology development. 



Information Management 



Offsite collections are repositories not only 

 of germplasm but also of information. This 

 information can aid collection management, 

 can provide more efficient access to specific 

 accessions, and might help develop collection 

 strategies. 



The current focus has been on standardiza- 

 tion of terminology in order to facilitate ex- 

 change between collections and to provide 



