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12-03-2004, 06:27 PM

(Mihai Cartoaje) wrote in message . com...
(David Hershey) wrote in message . com...

Many apple cultivars are self-sterile so cannot self-pollinate. Apple
orchards of these self-sterile cultivars must contain a second
cultivar as a pollenizer. Therefore, seeds of some cultivars will be
hybrids of two cultivars. However, each seedling with two parents will
be slightly different because of the "mixing" of genes that occurs in
sexual reproduction.

A possible explanation of the lower quality of most hybrids is if bad
genes are recessive, so alleles (hope I'm using the word correctly) of
hybrids would contain two recessive bad genes.

Maybe the bad genes shall be weeded out by further selection.

If you propose to do that, you will need much land and many years, as
seedlings will grow full size and will not bear (and cannot be
evaluated) for several years.

It isn't just a matter of deleterious recessive genes showing up in
the offspring of hybrids. While hybridization does seek to block the
expression of these genes, it is not the only or even the most
important objective.

The hybridizer seeks a particular combination of genes that gives
fruit of the desired qualities, and that desired combination of genes
is present only in the F1 hybrid generation; the F2 will be diverse,
and few if any of the seedlings will have the combination selected by
the hybridizer. If the experience of others is a guide, most of the
seedlings will produce either crab apples or no usable fruit at all,
and you may go through many generations and thousands of trees to find
one that not only produces satisfactory fruit but also breeds true.

--
Chris Green