Stewart Robert Hinsley wrote:
[...]

A question may want to ask is whether the seed size is controlled by
the maternal genotype (and environmental influences) or the embryo
genotype. If the former then you should be looking for the trees with
the largest average seed size, rather than the largest seeds
independent of source.
But your sieving process should preferentially select seeds from trees
producing a higher average size of seed, so this may not matter. You
still have to worry that the higher average size of seed is caused by
the environment and not by the genotype.

A very interesting project, though perhaps in danger of being overtaken
by genetic modification. Two further questions occur to me. One is, are
you selecting not only for seed size, but also for practical harvesting
characteristics? We need our grain crops, whether cereal, pulse, or
whatever, to stay on the plant when ripe, rather than scattering. The
other is, does alder seed /taste/ all right?

--
Mike.