170 » Technologies To Maintain Biological Diversity 



Box 7-A. — Definitions Relevant to Offsite Plant Collections 



Most offsite plant collections are devoted to as- 

 sembling a diversity of agricultural species, al- 

 though collections exist for wild species (69,112). 

 Offsite collections of agricultural crops can be 

 classified according to their principal goals. 



• Base collections focus on long-term preser- 

 vation of genetic diversity to ensure against 

 loss of valuable plant germplasm. Base col- 

 lections often include crops and their wild 

 relatives, typically maintained as seeds in 

 long-term, subfreezing storage. The base 

 collections important to agriculture in the 

 United States are held at the National Seed 

 Storage Laboratory in Fort Collins, Colorado, 

 a part of the National Plant Germplasm Sys- 

 tem (NPGS) (see ch. 9). 



• Active collections provide public and private 

 plant breeders and researchers access for use 

 in crop improvement, pharmaceutical studies, 

 taxonomic investigations, or genetic research. 

 Long-term security for plants in active collec- 

 tions is provided by duplicating their hold- 

 ings in base collections. Within the NPGS, 

 the Regional Plant Introduction Stations 

 maintain active collections for numerous 

 crops. 



• Genetic stock collections constitute an array 

 of plants with one or more unique genetic 

 characteristics. These collections provide 

 references for gene nomenclature and genetic 

 mapping studies. Leading research institu- 

 tions maintain many of these collections. 



• Working collections are held by pubHc and 

 private plant breeders and contain many in- 

 terrelated lines that serve crop improvement 

 activities. Working collections are commonly 

 obtained from active collections when new 

 characteristics (e.g., resistance to a new dis- 

 ease) are needed for crop improvement. The 

 genetic diversity in working collections is 

 frequently limited to the specific goals of an 

 individual breeding or research program. 



Many of these collections, regardless of their 

 specific goals, include a wide variety of acces- 

 sions. Accessions in offsite plant collections can 

 be classed as wild species, landraces, breeding 

 lines, agricultural varieties, and engineered lines 

 (18,46,52,103,115,116): 



Wild species related to agricultural crops are 

 of particular interest because they may pro- 

 vide new and valuable gene complexes. Others 

 may prove to be valuable sources for indus- 

 trial, forest, and pharmaceutical products. 

 But the bulk of wild species have no imme- 

 diately obvious use. However, offsite main- 

 tenance becomes important when such species 

 are endangered in their natural environment. 



Landraces have developed through genera- 

 tions by farmers who selected plants with 

 the characteristics they desired. They rep- 

 resent populations that can be genetically di- 

 verse and are often specifically adapted to 

 local environments and are considered to be 

 valuable sources for the genetic traits that 

 have enabled them to survive. However, a 

 landrace may be productive in one region, 

 but because it is so highly adapted, it may 

 not grow well in another. 



• Breeding lines are intermediate forms 

 produced in the process of developing new 

 agricultural varieties. Although saving all 

 such lines would be impractical, some have 

 permanent value to breeders (46). Probably 

 most valuable of the breeding lines are those 

 from which modern agricultural hybrids are 

 produced. 



• Agricultural varieties (cultivated varieties or 

 cultivars) can include those under cultiva- 

 tion as well as those no longer in popular 

 use. These generally are the products of 

 breeding and development programs. If still 

 widely being cultivated, agricultural vari- 

 eties are often not collected or stored, be- 

 cause they are considered easily available. 



• Engineered lines are the products of mod- 

 ern biotechnology. These are plants pro- 

 duced by methods of cell or tissue selection 

 in culture, culture-induced mutation, or 

 genetic engineering. Such materials are gen- 

 erally of more concern to scientists than 

 breeders. The promise of transferring traits, 

 such as nitrogen fixation or improved pro- 

 tein quality, may make such varieties impor- 

 tant. At present, though, engineered lines are 

 of minor concern to offsite collections. 



