Variance Effective Population Size under Mixed Self and Random Mating with Applications to Genetic Conservation of Species
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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 [N-e(v)] quantifies genetic drift. In this study, a model for calculating N-e(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, N-e(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 N-e(v) than with random sampling of seeds (RS), but ifs 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 N-e(v) equal to or greater than the actual size of the accession (N-e(v) greater than or equal to n). The importance of these two factors is enhanced as s increases. For arbitrary rates of selfing (0 less than or equal to s less than or equal to 1), under inbreeding equilibrium (IE) and with constant population size (n = N), N-e(v) can be adequately maintained through GC with a loss of less than or equal to 20% within accessions. For large sample size (n --> infinity), an accession Loss of less than or equal to 33% can be recovered. For maintaining adequate N-e(v), artificial selfing followed by GC is more efficient than accession regeneration by natural reproduction. For achieving appropriate N(e(v))s, increasing the rate of self-fertilization in polymorphic materials makes collection more difficult but regeneration easier for minimal loss (less than or equal to 20%) within accessions.
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