01972naa a2200193 a 450000100080000000500110000800800410001910000140006024500420007426000060011630000080012252015340013065000120166465000130167665000160168965300130170565300120171877300480173016463641993-11-10               bl ---       0--  u    #d1 aGEPTS, P.  aGenetic markers and core collections.  c0  a2p.  aAccording to the definition of Franlel (1984), a core collection is a subest of the general or bulk collection that representants the genetic diversity of a crop species and its relatives with a minimum of repetitiveness. One of the essential questions, therefore, in the establishment of a core collection for a crop species is the determination of patterns and levels of genetic diversity in that species. This information then will guide the sampling process leading to the instituition of a core collection. For example, groups that are more diverse will require a storanger representation in the core collection than more unifom groups. Likewise, the sampling procedure should be capable of capturing locally abundant unusual variants. How does one then characterize the genetic diversity of a species? Various criteria have been suggested, including toxonomy, geography, ecology, characterisation data (including morphological, biochemical, and molecular markers), and agronomic evaluation data (Brown 1989). IN my presentation, l will discuss the role, advantages, and disvantagens of biochemical and molecular markers in the characterization of genetic diversity for the purpose of establishing a core collection. The main advantage of biochemical (isozymes, seed proteins) and molecular markers (RFLPs and PCR-based markers) is that they are genotypic markers. They directly reflect reflect mutational changes at the DNA level without influence from the environment and, hence, allow us to equate genotype and phenotype.  aAbacate  aColheita  aPopulação  aHibridos  aPlantas  tDavias, CA: University of California, s. d.