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Re: F2 and open Pollinated varieties versus F1

This PM, Duncan McAlpine <dm2477@lab3.ca.boeing.com> asked:

> Subject: F2 and open Pollinated varieties versus F1
> Date: Tuesday, April 08, 1997 4:12 PM
> Does anyone want to try an explain what this means to the average grower?

OK.  Bear with me, please.  I will try to approach this from a genetics
point of
view, as well as from a seed industry point of view, and from the home
gardeners point of view, too.  

To make a true F1 hybrid, you need to develop at least two inbred lines,
one for the seed parent, one for the pollen parent.  In practice, you make
many more than two, make all possible combinations, and choose the best
performing hybrid combinations.  Inbreds are made through self-pollination,
which can happen naturally (most garden legumes, lettuce, tomatoes, 
impatiens); by hand (cucurbits, pansies, petunias); or not at all (most
Brassicas).  

The actual cross that produces the seed from which you grow an F1 plant is
often done by hand (many vegetables and flowers); by wind (maize --- take a
trip through the Midwest when they are detasseling --- the process is
pretty amazing [no pun intended]); or by insects (carrots, onions, some
Brassicas).  Using insects requires caged or screenhouses, and raising
pollinators in isolation, but it's do-able.  I watched hybrid ageratum
production once: the workers used modified Dustbusters to collect the
pollen from greenhouse grown pollen parents, and just dusted the pollen
onto the seed parent flowers with a brush.  

That's the F1.  Seed produced by an intentional cross on an inbred seed
parent will produce F1 plants.  

You get an F2 population by allowing an F1 plant to self-pollinate (or
doing it by using one of the crossing methods above).  Selfed seed produced
on an F1 will produce F2 plants.  

An open-pollinated population is produced by random pollination of every
plant in a population, and presumably giving you all possible combinations.
 In some species, o.p.s are relatively uniform (tomatoes, peppers,
impatiens); in others, o.p.s are not very uniform (maize).  

Why F1 hybrids?  Because there exists a genetic phenomenon called hybrid
vigor.  F1 maize outproduces o.p.. maize by a factor approaching 2X, and to
a commercial farmer that is critically important.  However, F1 tomatoes or
cucurbits give little if any yield increase.

Why F1 hybrids if no increase in yield?  Because every plant in an F1 is
identical (for practical purposes: there can be some genetic variation in
the inbreds that gets multiplied when the inbreds are crossed).  This
uniformity can be advantageous when you are trying to harvest a field at
one time, by a machine.  But it may not be an advantage to a home gardener.
 After all, how many bushels of tomatoes can you use all at one time?  For
a home gardener, an o.p. may be better.  

BUT... a seed company makes a lot more money from hybrid seed than from
o.p. seed.  Therefore, they put all of their breeding research into hybrid
development.  How much difference?  A pound of F1 tomato seed at wholesale
goes for between $500 and $1,000.  O.p. tomatoes go for $2 to 10 per pound
(this is at wholesale, remember), depending on yield.  Which would you
rather be producing?  

The impact on the home gardener is that all of the best genetic
combinations (disease resistance, especially) are only available as
hybrids.  No one, and believe me, NO ONE (regardless of what the catalogs
tell you), actually breeds for the home gardener, and no one breeds o.p.
varieties of any crop once F1 hybrids are commercially feasible in that
crop.  Vegetable breeding serves the major produce markets (fresh, frozen,
processed); flower breeding serves the large greenhouse grower.  The home
gardener gets what spills over.  Granted, the spillover can be substantial
(and some seed distribution companies [Johnny's, for instance] do a good
job of trialing for the home gardener), but the home gardener market
consumes too little seed (in comparison) to have it be a primary R&D
direction.  

You need to realize that it is not practical to produce F1 seed for every
crop.  Phaseolus (dry and snap beans), for instance, or any legume. 
Although, F1 seed is theoretically possible, it is not very practical. 
Each pollination takes many minutes to do, and only produces 8 - 10 seeds. 
In much less time, each hybrid pollination on tomato produces hundreds of
seeds.  Similarly, there are practical limitations at producing F1 seed
from many plant families (such as mints or composites).  

Each F1 geranium (Pelargonium) seed wholesales for 10 to 12 cents.  That's
because each geranium pollination produces a maximum of 5 seeds.  And the
cost would be many times higher if the seed were produced anywhere but in
the Third World.  My best guess is that 50% or more of the world's F1
geranium seed is produced in central Africa, at a labor rate of a few
dollars PER DAY.  Similar production costs occur for many F1 flower and
vegetable seeds.  

What would I grow?  
If I were a commercial vegetable farmer, or greenhouse grower of bedding
plants, I would grow F1s.  Without question.  And with every crop that I
could.

What would I grow?
For my home garden, a mixture of F1, F2 and o.p.s, depending on what
performance I wanted from each crop, and how much money I had to spend.  

Regarding seed saving: you can safely save seed from o.p.s.  The seed
should perform like the original, unless it gets crossed out by accident. 
Stick with beans, lettuce, tomatoes and peppers, and you should be safe.  

If you self an F1, you get an F2.  The maximum amount of genetic UNIFORMITY
exists in the F1.  The maximum amount of genetic VARIATION exists in the
F2.  In a true F2, each and every plant is different, and will behave
differently.  Personally, I would not bother to save seed from F1s in the
garden.

If you let a population of F2s cross at random, you get an F3 population. 
And if you continue the process for a few more generations, you get an
o.p..  

Duncan, I hope this is what you were looking for.  It's a pretty massive
tome for e-mail.  If there are questions, direct them back to the list so
that this discussion can continue.
Rick
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