Variance Effective Population Size under Mixed Self and Random Mating with Applications to Genetic Conservation of Species
- Roland Vencovskya and
- José Crossa *b
When collecting and regenerating genetic resources, genetic drift affects the representation of a population and occurs at two stages: when sampling the parents and when gametes are sampled from these parents. The variance effective population size [Ne ( v )] quantifies genetic drift. In this study, a model for calculating Ne ( v ), that considers the two-stage sampling of mixed self and random mating species, is developed. For germplasm collection, as the rate of natural or artificial self-fertilization (s) increases, Ne ( v ) is reduced and becomes increasingly dependent on the number of seed parents (P) and is less influenced by the number of seeds sampled per parent (n/P). Female gametic control (GC) leads to higher Ne ( v ) than with random sampling of seeds (RS), but its effect is tangible only when n/P is small. For accession regeneration, maintaining accession integrity (the proportion of functional parents, u) at an adequately high level and adopting GC are required for assuring Ne ( v ) equal to or greater than the actual size of the accession (Ne ( v ) ≥ n). The importance of these two factors is enhanced as s increases. For arbitrary rates of selfing (0 ≤ s ≤ 1), under inbreeding equilibrium (IE) and with constant population size (n = N), Ne ( v ) can be adequately maintained through GC with a loss of ≤20% within accessions. For large sample size (n → ∞), an accession loss of ≤33% can be recovered. For maintaining adequate Ne ( v ), artificial selfing followed by GC is more efficient than accession regeneration by natural reproduction. For achieving appropriate Ne ( v )s, increasing the rate of self-fertilization in polymorphic materials makes collection more difficult but regeneration easier for minimal loss (≤20%) within accessions.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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