24 August 2012

Re-thinking crossing strategies

Well its almost a year since I germinated my first peas to develop an antipodean purple snow pea. And I've had a chance to take stock. I dived in, without thinking through a strategy to optimise success. In part, this was due to some time pressures - rationally assessing each variety, sitting down and thinking through possible crosses, and then waiting another year to do the crosses just didn't fit with my impatience to get cracking. So I sowed every purple. yellow and snow I could lay my hands on, and crossed as much of everything with everything else that I could, given the constraints of time and available flowers at the right level of maturity.

Problem is, I now have not quite enough seed of any one line to really explore the F2 outcomes, and too much seed of multiple crosses to be able to grow out with a good chance of success this season.

A smart approach would have been to select one purple (since my guess is the three purples available in Australia are probably all the same anyway), choose a good, tasy, disease resistant, dwarfing, multi flowered snow pea of good taste, and do multiple crosses between them to get a big whack of F1 seed to grow out over summer, with a resultant 300 - 400 F2 seeds of one line to try in autumn.
Instead, I've got (or will get) about 100-150 seeds of about a dozen crosses - not quite enough to be confident of getting the desired class in one season, which could be refined , stabilised, or outcrossed for missing phenotypes in subsequent generations. It looks like I will need a few extra generations to get the classes I want, so leaping in without proper planning in an effort to get results more quickly may have backfired. This season will tell.

While the summer growouts did give some F2 seed, even sowing these as soon as I got them didn't really give me enough time to grow out the F2 plants for F3 seed this spring - my plants are just setting pods - they were very slow over winter, and some flowers didn't set seed during the winter cold - and now is when I should be sowing the next generation to escape the hot November when seeds won't set, but the pods on the F2s are onlt just developing. Let's hope for a long spring (but with an El Nino expected, I don't like my chances).


  1. I found my way here from the Homegrown Goodness forum. Where will you go from here?

  2. Linda, time I made another post on progress to date. I've got a few purple and half purple snows as a result of my spring/summer growouts, and I've just sown some F3 and F4 seeds for an autumn crop.
    Thanks for your comment.

  3. Ah, your other post must not have the "Peas" label, so I haven't found it yet!

    Are you growing 2 generations a year, then? I'm considering doing something like that, but I had poor luck with my Fall crop last year...probably due to inadequate watering right after planting. Of course, that's months away, and we'll cross that bridge when we come to it.

    1. Linda,
      I've tried 2 and 3 generations per year. I can get a spring crop without any problems. If I plant the seeds from that crop straight away, and try and grow over summer I can get some plants up, but growth is pretty marginal in my hot dry summers, and I have to grow in the shade. Even then, the plants have poor production, and I don't think the plants are representative of growing in normal seasons, which makes selection problematic. OK if I just want to grow out a few F1s to get F2 seed. Planting this seed in autumn for a third crop is also less than perfect. Two weeks difference in planting times in late summer - 2nd week of February ere, gave me some seeds before winter, but 2 weeks later plantings didn't produce until spring, 5 months after planting.
      At least that was last year's experience. Trying to tweak it a bit this year to see if i can get 2 or 3 good crops a year
      Planting green seed works for some varieties, which can save 3 weeks or so in drying down the seed, and then resoaking for sowing.

    2. You're lucky to have a Winter that's mild enough for growing peas at all! I can reliably get a Spring crop, planted in mid-March, and some people in my area manage to get a Fall crop if they plant in late July. I haven't (yet) had good luck with this myself, but hope springs eternal.

      I've found a few varieties of shelling peas that are very small, supposedly 6-12 inches in height. Some of these, ate least, are supposed to be extremely cold-hardy, and theoretically do well in a cold frame. I'm about to undertake a project to breed edible-podded peas that are equally small, early, and cold-hardy. Once I get past the point where I've selected for ones that are all very small, I might be able to manage a 3rd annual crop in a cold frame, or indoors under lights. The F1s should all be tall, however, so I'll need to decide whether to try for a Fall crop this year or not.