Breeding Sweet Potatoes (turning them into a seed grown annual)

[reed]

Not much happening with the sweet potatoes right now. It's been too hot for the last several days to do much in the garden. I did make a new video of current conditions of the plants.
 

[reed]

It's getting quite chilly here in the early mornings and I'm about done harvesting sweet potatoes. Still need to take cuttings of the non-rooting ornamentals to grow as house plants over winter and still two volunteers yet to harvest.

I only found three more breeding group candidates from the pot grown plants. That is a bit disappointing and surprising since I got five from the inground patch and they all came from the same batch of seeds. I kept them watered good I thought, but apparently not good enough as the ground under the pots was still very dry so the feeder roots had not exited the drain holes on most plants. Also, even though each one had its own pot they were still overcrowded and a half dozen oversized vines were crowding the others. The leaves mostly looked so much alike that once they merged into together, I couldn't tell that just a few were dominating and hogging up all the sunshine. Some smaller plants with a nice clump root and compact growth habits produced very little.

All that has me thinking that I have a lot to learn about growing sweet potatoes. Always focusing largely on the genetic ability to make roots and seeds I've overlooked environmental factors of root production. You get the seeds anyway, but I think better conditions would make for better roots, and I think I have probably unnecessarily discarded a lot of good ones over the years. I'll be changing that next year with better soil mix and much more attention to making sure it is consistent for all plants. Also, less overcrowding and more attention to watering. 

Next year should be easier overall as I will just have my breeding groups instead of a hundred new sprouts to mess with. I figure on having just four or five of them spaced here and there with two or three plants together in one of my large tubs. I have them already emptied and rinsed out and piles of tomato and bean vines and corn stalks ready to turn into soil. I have three more tubs that grew successive crops of bush beans and okra, I'll dump them and mix that up with the vines and stalks along with some grass clippings and leaves. I also have the nitrogen nodules from a bunch of peanuts buried in some compost, I'll put that in the bottom of each tub and let it all sit and compost a bit over winter. I don't want the corn stalks and tomato vines to completely compost as they provide the stuff to keep the soil loose and fluffy, which I think is good for root production. I also keep the stems of some big ornamental grasses to chop up and add if I think more fluffy stuff is needed but I won't do that until spring.

 

[Carol Deppe]

I think focusing on the breeding groups for a while is a good strategy. The groups would allow those who want to grow your most established material to start growing it. If they started from vegetative material, they could just grow your groups without needing to do any breeding at all. And could just start collecting seed themselves as a backup/resilience plan. However fascinating we find traveling into the unknown and breeding new varieties, most farmers and gardeners just want to grow an established variety they really like.

The practicality of the breeding groups as a way of distributing finished "varieties" depends a lot on how many members are in the group. Once you have a breeding group of three or four clones that work,it might be worth while to figure out whether there is a combination of just two of the four that would work just as well.

The approach you are exploring should work equally well for potatoes.

[reed]

The approach you are exploring should work equally well for potatoes

I've wondered that and why, to my knowledge no one has done it already. I still grow some potatoes, but my climate isn't the best for them, and I don't have a good place to store them so the fact that they don't really make anything to eat or really even much to evaluate (from seed) makes working with them really hard. I remember seeing a video one time from a grower in coastal California that got some not huge, but pretty nice potatoes, from seed. I wondered if they could do the same as I did with sweet potatoes and just grow clones of those nice ones and keep backcrossing and selecting until they had a line that really did have good chances of making a harvest again, from seed. I don't think that grower followed up. Patience is critical in such matters, I think.

I'm rethinking my plans for my sweet potatoes next year; I'll get back to that later. Below are plants I'm keeping as houseplants this winter because they didn't make large storable roots but are very seedy. I've always mostly just discarded plants such as these but decided it might be a good idea to make a "super seedy" side project away from the others. I'll keep them on the patio or in the back garden.

These are four very seedy new plants ready to come into the kitchen window when it gets cold. The two not in line in the tray are just the old Miss Bloom and Likes to Climb. The six cell pack on the right is Bean Patch Volunteer. It is very seedy, nicely bushy and has potential to be a root producer. The six in the middle are two that came from seeds I planted and that are both very seedy, although poor rooting. The six pack on the left are another volunteer, again with potential for better rooting than it did this year.



As far as rethinking my plans, it's more rethinking my technique. You can see in the photos they have seed capsules in development, as well as flowers and flower buds in various stages of development. I know from years past that that will likely continue even after they go inside and light and temperatures decrease. The reason I know for sure that the plant Miss Bloom is self-compatible is because it fully matured seeds in January a couple years ago when I hand pollinated it.

As I looked at these, I realized without bees to interfere I can do the same thing with all of these and find out which is self-compatible and which is compatible with which else. I can easily do that in the patch next year too, either by taking individual cuttings inside or by bagging stems with lots of flowers. (I already bought some soft mesh bags)

I'll still do my breeding groups, but I don't have to wait to find out compatibility preferences of each plant. It won't be all that much trouble to identify for sure any self-compatible plants as well as compatible pairs just by isolating cuttings or bagging branches. If I find any self-compatible plants especially in my culinary group(s)it will be very interesting in 2028 to see how they turn out.

The first seeds I ever saw came from a self-pollinated plant and I've always wondered about the potential involved with it how often it occurs and so on. I of course don't know but I suspect inbreeding depression is not a big concern with sweet potatoes. I suspect it's more likely that multiple phenotypes will still result even from self-pollination.

[Carol Deppe]

It would be really cool if you can figure out which plants are self-compatible. Especially if any of your culinary lines are. And selfing such a line would certainly give you a greater percent of seed that give offspring similar to the parent than crossing to something else.

I agree that even with recurrent selfing a sweet potato plant would likely be nowhere near breeding true for very much for a long time if ever. Not with six copies of each chromosome.