This is a public-interest archive. Personal data is pseudonymized and retained under GDPR Article 89.

Tomato dehybridizing (Was: Garden layout question)

Hi Tony,

You wrote:

[...]
> This reminds me. A couple of days ago, somebody spoke about
> dehybridising hybrid tomato variety. How do you go about doing this? Do
> you just plant saved seeds for a few generations, saving seed from
> plants exhibiting the desired characteristics until the level of variety
> in new plants falls below some threshold?

Exactly.  Tomatoes are strongly inbreeding, so it doesn't take as many
generations to reduce variability down to the point where you'd have a
relatively true new variety as it would with an outbreeding vegetable such as
corn.

If you selected down to the single most desirable plant each generation you
should see the amount of variability drop by about half per generation - as I
understand the genetics that is, someone please tell me if it's otherwise!  Of
course the more plants you grow per generation the greater your odds of getting
that ideal combination of all the desired traits.

The amount of variability you see in that first generation of saved seed depends
on how different the parents of the hybrid were from each other.  If you
perchance see no variability that first generation then the parent was likely
not a hybrid at all - in fact some advertised hybrid varieties are actually open
pollinated.  For example, Sweet 100 "Hybrid" is alledgedly such a variety -
although I haven't tried it myself it will supposedly grow true from saved seed.

> I'm intrigued, because all the volunteer tomato seedlings in my garden
> nearly always turn out to be some sort of cherry tomato.

Some varieties of tomatoes have long styles which stick out beyond the rest of
the flower - some heirlooms and those with wild species in their ancestry have
this trait.  They are much more subject to cross pollination by wind and
insects.  Could that explain the preponderance of cherry-fruited offspring in
your case?

Most varieties are strongly self-pollinating - the style and stigma lying within
a cone of fused anthers.  The stigma becomes receptive and the pollen begins to
drop while the flower is still in the bud stage.

However, that doesn't mean that different varieties planted closely can't or
don't cross with each other.  How much distance is needed to isolate varieties
is a controversial subject.  Some say there is very little crossing even when
planted next to each other while others think you need at least 30 meters.

Solitary bees are likely the major north american insect pollinator of tomatoes.
Enclosing plants with a mesh fine enough to keep the bees at bay will minimize
cross pollination.  For you and me though it's probably a lot easier to cover a
single truss of unopened flower buds with a bag made of fine mesh, removing it
once the fruit is set and tagging them for collection later.  That would provide
more than enough seed to start dehybridizing.

If you're interested in saving seed and developing your own strains check out
_Breed Your Own Vegetable Varieties_ by Carol Deppe, published by Little, Brown
and Company, 1993.  She details the principles behind breeding and selecting
plants, providing home growers with the techniques to develop superior strains
which are best adapted to their own gardens and needs.

> Tony Lupton                      *           Email: t.lupton@citr.com.au
> CiTR Pty Ltd                  *    *         Phone: +61 7 3259 2382
> 339 Coronation Drive              *          Fax  : +61 7 3259 2259
> Milton Qld 4064
> Australia                       *

   ____________________
  |                    |
  |     Bob Carter     | Kootenay Bay   Zone
  |  bcarter@awinc.com | BC, Canada      6b
  |____________________|
Follow-Ups: References:
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index