Wednesday, January 14, 2009

Tomato Breeding

To help me with my tomato experiment, I spent all my free time yesterday reading about tomato breeding and genetics. Wow. There are a ton of genes that they know about (and that link is just a sample). I learned some interesting facts, not all of them about tomatoes either.

The most important fact was that unlike most modern tomatoes, the Sungold plant has long stigmas that stick out from the cone of the anthers. Most modern tomatoes hold the stigma inside the anther cone, so the modern tomato is always self-pollinating. Well Sungolds aren't always, nor are some old Heirlooms and wild tomatoes. They are free to cross with any tomato close to them, though still often cross with themselves. I had two other tomatoes in my garden - Aussie and Orange Blossom. Did they cross with my Sungolds? I did have bumble bees working the tomatoes last year.

I read that sometimes you want to select plants that have some traits that you like then recross them back with the origianal plants. I'm not going to do that. To do that you have to isolate the flower and strip it of its anthers before the pollen is viable, then hand cross it. Nah. Maybe some year. Right now I'm just going to let them grow and see what I get. I'll pick the best and save seed from those.

I learned that the Mi gene gives resistance to the root knot nematode (along with some aphids and whiteflys), but it works much better as a hybrid. If it carrys two copies of the gene (which an open pollinated plant would), it doesn't work as well. Too bad. I'd love to have that resistance in an OP tomato.

The most shocking thing I found out was not about tomatoes at all. Brassicas are self-incompatable for pollination. I knew that apples and blueberries need different pollinators, but figured all the garden vegetables have been bred in the past to be open pollinated homezygous plants that would breed true from themselves. Brassicas actually don't like being homozygous. Even if you cheat and bud pollinate them (a technique where you polinate the stigma while the flower is just in bud) they oftens still don't like to grow because they like their genetic diversity.

With all this new knowledge, I'm still going to do just what I was before. Plant them; see how they grow; save the ones I like. I would love to learn more however. The subject of plant breeding is really enthralling. I've followed Daughter of the Soil this year in her amatur plant breeding of peas and was facinated. I've been looking at books too. I'm thinking Breed Your Own Vegetable Varieties: The Gardener's & Farmer's Guide to Plant Breeding & Seed Saving would be a good introduction. It is an older book and some of the story line is a little out of date, but the breeding and saving parts are still up to date.


  1. A fascinating and informative post. I've just gotten started with seed-saving in the last few years; and so far have only saved nasturtium, morning glory, fennel seed and dill seed. I'm definitely going to also save some vegetable seeds this year. I too have followed Rebsie's adventures with peas at Daughter of the Soil, but breeding may be a ways down the road for me. :)

    I love your blog and will return again (and again). Thanks!

  2. Hi Daphne, also I have now joined the 'challege seed to seed' I think it is a brilliant idea.
    That is by the rule I already 'live' but it is always something new to learn.
    xoxo Tyra


  3. Very interesting Daphne. I am involved in developing my own line of tomatoes, so as to get dwarf lines. ( we have windy conditions, and they won't require staking as one of the benefits) I've successfully crossed several and some are now in their F5 generation so nearly stable. I'm going to try some more using Tatura Dwarf as the 'father' and a couple of other heritage and nearly lost varieties. It is fascinating. I've added you to my blogroll so I can keep up with your exploits!

    1. Hi

      I am trying to experiment with tomatoes as well to get dwarfs with long shelf-life. Are you able to assist in any way?

  4. deborah, her blog is just too much fun to read. I can't wait until spring and she writes more about her peas.

    Tyra, Fabulous. I think the idea is wonderful too. It gives you a real feel for the whole cycle of the plants.

    Cosmic, that sound very interesting. I'll have to go farther back in your blog and see the plants.

  5. Cosmic,
    I have a pretty strongly determinate(~2ft height) tomato variety from a cross I made from silver fir and yellow pear if you are interested in something to evaluate for the dwarf line you want. It is also the earliest to start ripening for me, after about 60 days from transplant. I have seed from about 3 generations of outgrowth that are pretty stable.

  6. Thank you for the offer, Geoff. Unfortunately our quarantine rules are very strict and I can't bring in seeds from overseas for fear of dire consequences. So all my breeding has to be 'in-house'. Thanks again for the offer. Sounds interesting. Silver Fir is a unique plant, I love its form and the leaves would certainly be easy to identify!

  7. Ha, Helps if I look where you are located. Apologies, didn't mean to lead you on.
    Best of luck.