Re: avocados -- genetics -- skip if the subject bores you

In a message dated 10/15/98 9:10:52 PM Pacific Daylight Time,
Pollinator@aol.com writes:

<< 
      The fact that seedlings do not come true to variety should tip you off,
 Janet, that cross pollination is taking place.
  >>

Sorry it has taken so long for me to respond to this.  

Actually the above statement isnt always true.  It might be true if the parent
plant producing the seedlings is from a pure genetic line (homozygous),  but
if the plant concerned is of hybrid origin(heterozygous),  the off-spring,
even from self pollination,  could exhibit the entire range of characteristics
ranging from one parent to the other.  That is why seed saved from heirloom
self pollinated varieties of tomato breeds true,  but seed collected from self
pollinated hybrid tomato varieties doesnt.   

I do agree that in general it is far better for plants, evolutionarily
speaking,  to be out-crossed as much as possible to insure genetic
variability.

<<Other research with Fuerte showed as much as 50% increase in production
when cross pollinated.>>

Here in so calif,  you can plant single avocados in your yard,  and be
assured,  if there are enough local pollinators,  that there are numerous
trees in your vicinity to insure cross-pollination.  But perhaps if you are
growing avocados in a part of the world where they are less common,  your crop
might be enhanced by growing two varieties.  If you grew two trees of the same
variety,  that wouldnt get you anywhere, because if they are grafted,  it is
the same as growing clones with identical genetic make-up,  and hence no out-
crossing.

This makes me wonder,  if all of the avocados in some of these extensive
orchards are the same variety,  and hence clones of identical genetic
information,  isnt pollination between different trees the same as self-
pollination?  so then,  technically isnt almost all pollination in these
uniform orchards the result of selfing?  Isnt this also true of almost all
groves of grafted trees?  And if out-crossing betweem different genetic lines
increases fruit production,  wouldnt it be better to plant two compatible
varieties interspersed in an orchard to increase over-all production?

janet
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