See more from this Session: Plant Genetic Resources - the Mysteries of Maize
Wednesday, October 19, 2011: 3:00 PM
Henry Gonzalez Convention Center, Room 214A
In an ideal infinitely large population without mutation, migration, and selection, gene
and genotype frequencies remain unchanged over generations. However in finite real population,
gene frequencies fluctuate randomly over generations due to finite sampling of gametes therefore
the census population cannot explain the effects of inbreeding and allele frequency drift. The
concept of effective population size is considered a fundamental measure of representiveness of
a sample of individuals (plants, animal, humans) in evolutionary, quantitative genetics, breeding,
and genetic resources conservation.
Genetic models based on the number of male and female gametes contributed by individuals of
monoecious plant species have been developed based on variance effective population size applied to
the context of artificial selection (Vencovsky, 1978) and to specific aspects of genetic resources
conservation (i.e., collection and regeneration) (Vencovsky, 1978; Crossa and Vencovsky, 1994).
Crossa and Vencovsky (1997) and Vencovsky and Crossa (1999) showed the theoretical developments
and practical applications of the variance effective population size when drift occurs at two
stages, (1) sampling parents for reproduction and (2) sampling gametes (offspring) from those
parents for monoecious populations and for populations under mixed self and random mating.
For the case of several subpopulations, variance effective population size becomes dependent on
the allelic diversity among populations and the number of subpopulations. When a single population
is considered and seeds sampled have a family structure, at the limit variance effective population
size depends only on the number of seeds parents and the coancestry coefficient among sibs within a
family. Accession regeneration is the case where reference population is finite and gametic control
is a major factor allowing to recover loss up to to 20% of seeds.
See more from this Division: C08 Plant Genetic ResourcesSee more from this Session: Plant Genetic Resources - the Mysteries of Maize