§A persistent question has been, what is the effective
population size, Ne, of our breeding stock?
§A famous rule in conservation genetics is the 50/500 rule,
which states that an Ne of 50 is the minimum effective population size needed to avoid
immediate collapse of a population from inbreeding depression while an Ne of 500 is needed to
counterbalance the
slow loss of alleles due to genetic drift by the addition of alleles from
mutation.
§We are trying to use 20 American lines per source of
resistance per locale. Twenty lines yields an inbreeding
effective population size of about 70, so it satisfies the 50 portion of the 50/500
rule.
§We can only handle three sets of 20 American lines at
Meadowview, or 60 lines total.
§The remaining lines to achieve the 500 portion of the
50/500 rule come from our state chapter breeding programs.
§The state chapter breeding programs also add adaptation to
their local conditions: we do not expect trees from Virginia to grow well in Maine, for
instance.
§