Sweet potato breeding project - generation 1

First to flower and first to set seed -
seedling from a purple-leaved variety.

Let's talk batatas! Last year I managed to get some of my sweet potatoes to flower and produce seed, a first step towards breeding new, and in the long-run hopefully more cold-adapted sweet potato varieties. Since true sweet potato seed is a bit of rarity (at least in these parts of the world) and plant breeding significantly benefits from collective efforts (and since my own gardening successes tend to be somewhat erratic), I figured it would be wise to spread the responsibility a bit and so I distributed about half of my seed to other growers. I also received some seed back in trade, so that in total I had seed from 4-6 parent varieties. All of these were sown sometime in the beginning of April (if I remember correctly). Germination rate was high (it helps if you scarify the seed first), probably around 90%, and I ended up with some 50-ish seedlings of varying leaf types and growth habits. These duly went into the garden in the second half of May, a bit earlier than the varieties I'm propagating from slips. I took cuttings from most of the seedlings so that I would have at least two plants of each new variety, just as an insurance policy against unforeseen circumstances - think inadvertent gross neglect or sudden rodent mayhem.

Flower bud abundance

I cover all my sweet potatoes with a floating row cover until they start flowering, which happened surprisingly early for the seedlings. The first flower buds appeared at the end of June, when most of the plants were still fairly small, and by the end of July some of these seedlings were flowering prolifically. I'm not sure if this has something to do with the fact that seedlings were raised indoors, and that they were therefore subject to a fairly large change in temperature when they were planted out (though to some extent so were the slips, and they didn't respond in the same way), but it's something I plan to investigate further. Most of the plants that are flowering are putting out an abundance of buds, not unlike the variety Purple, which is likely to be one of the parents. In fact, all of my own seed is probably a cross between Purple and Bonita. I noted four flowering varieties last year, but I've since become convinced that the variety I named 'Nordic White' is actually Bonita, while Georgia Jet really only produced a handful of flowers at most, and even then late in the season.

Except for some hesitant hoverflies, the bees and bumblebees didn't seem all that interested in the flowers at first. I suppose that's what I get for seducing them, right next to the sweet potatoes, with a generous patch of lacy phacelia (Phacelia tanacetifolia), which is a veritable bumblebee-magnet. For a while I also didn't see any evidence of seed formation, but something has been busy with those flowers, because after returning from a trip abroad and rushing out to the garden today I found some seed pods on the plants that were flowering first (top picture). Bless you, loyal mysterious pollinator. To be fair, now that the phacelia is done flowering I've seen a number of white-tailed and red-tailed bumblebees on the sweet potato flowers. Together with the fact that the diversity of I. batatas genetic material in my garden this season is a lot higher than last year, I'm hopeful I'll get a good amount of seed by the end of the season. Since we're having a fairly average summer so far, with plenty of rain and so far very few really warm days, that would be a significant indication that I am able to get true sweet potato seed under normal environmental conditions here in southern Sweden. A few seasons of that and I might have reliably-flowering breeding material from which to start selecting for early and temperate climate-adapted tuberization. We're not quite there yet, of course, and it seems like temperatures will be staying below 20℃ over the next two weeks. Fingers crossed!

True sweet potato seed forming

Part of the sweet potato patch - 12 August

Apart from the seedlings, I'm also again growing the best from last year's varieties - Bonita, T65, Nordic Orange, Georgia Jet, Purple, as well as one of my Papua New Guinea seedlings from last year (Papua White-16), an old heirloom called Patriot, and two improved American varieties called Orleans and Bellevue that I received through the people at SLU Alnarp (the Swedish Agricultural University, who are currently also doing tests with growing sweet potato in southern Sweden). As last year, I noticed flower buds appearing on some of these plants by the end of July, and today I saw that Bonita has started flowering. Overall, I would say that things are going pretty well for the sweet potatoes. I lost three seedlings, probably to the voles, but that's it so far. To be continued!