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

[Lauren]

I tried to overwinter 6 plants--none of them lived. I had roots from those same six plants--none survived. So what I have is the leftovers from the minuscule "harvest" last year, plus seedlings. Working on slips right now from the remaining roots, but I didn't keep track of which was which so recordkeeping is right out the window.

The interesting thing, though. I decided to plant all the original seeds, maybe 30 left. I like breeding longevity into my seeds (i.e., supporting the existing longevity) so I'll plant last year's seeds next spring.

Anyway, I decided that the most important right now is the ability to germinate without nicking the seed. So I had the bag with the seeds on a heat mat and picked out the seedlings as they sprouted. After about a month of this nothing else was sprouting or even looked close so I dumped what was left in a pot out in the unheated greenhouse. Six came up. There might have been more, but I accidentally dumped dirt on them so who knows?

After all that careful planting, tending, blah, blah, blah, they started sprouting after I put them out in the cold.

Your cold tolerance may already be there, and the seeds that are cold tolerant just weren't sprouting because the conditions weren't right.

[reed]

They are a little weird in how they sprout, I still don't know exactly what conditions are best but they commonly volunteer now and those I sprouted directly in the ground last year did great. Some sprout in a couple of days, some months later.

Most of those I'm cloning this year were from those direct seeded so I hope to really reinforce the easy sprouting trait in this years seeds. I discarded most that were sprouted in the cold frame last year in favor of the direct planted ones. I feel kind of bad discarding seedlings, or plants after just one season but just don't have room for too many.

I have never saved this many for cloning before, 25, and am noticing a significant difference in how easily they produce slips. I think that is a good trait too so have discarded 5 that are showing no sign of making slips. An easy choice because they were also my least favorite of the group. So down to 20 now, easier for me to manage. All good seeders and all good quality roots but they don't all have my preferred clump root and bushy growth traits.

I'm thinking if all goes well the seeds produced this year will be an elite line where chances of all the good traits are greatly increased. Then maybe next year I'll start some of the older seed and find some more with the clump root and bushy habit to cross in future seasons with the elite line.

Also growing in much better soil conditions this year to get an idea of actual production from the various ones. I have three or four that assuming they produce good roots in quantity as well as seeds I may keep cloning them for a while longer, maybe even give them names.

*That one little one that is the best flavor I've ever tasted and all of whose larger specimens were accidentally eaten has not sprouted slips. Bummer, but it also has not rotted so there is still a chance it won't be lost.   

[Ferdzy]

Maybe something to consider, Reed: We almost discarded one of our garlic varieties because it is so slow to come up in the spring, and makes smaller heads. But then we realized that it is the last garlic to sprout in storage, staying good right into June. So now we grow smaller amounts and save it for last. So it might be possible that the slow to slip ones may also be the best to store.

[reed]

I wasn't going to bring that little issue up but is has occurred to me that you wouldn't want them sprouting too soon and several did have little nubs that took off as soon as I applied water and light, one already had several sprouts about 1/2 inch or so. Similar ones in the food store bin don't seem to be degraded even though they have the little nubs.

Still, probably best not to go too overboard in encouraging that trait but I imagine there is a happy medium in there somewhere. Another thing is some have lots of sprouts and some only a couple. The more the better I think but only at the appropriate time. Some seem to sprout mostly at the end that had been, what I guess you would call the top and some have them all over.

They are just so crazy variable in pretty much all aspects. I figure you'd have to grow out about a 1000 of them to get enough meaningful data to really start figuring it all out.

One of the things I'm most interested in next is to start putting together the compatibility puzzle. I already know if one is self compatible then pretty much all flowers are pollinated. If not self compatible then flowers close to another one are all pollinated but only some on branches farther away are. It might not be hard to isolate some that are self compatible.

Here are my suspected possibilities on compatibility:
1) Self compatible
2) Self compatible & compatible with any other
3) Not self compatible but compatible with any other
4) Self compatible and compatible with just some other(s)
5 )Not self compatible but compatible with just some other(s)
6) Any of the above but only in one direction or the other
7) Not compatible at all
And probably more I haven't thought of

For now, if I go to the effort, it will be just to try to identify some self compatible ones.

[AndrewB]

Sounds like this project is really making progress. Can't wait till I can grow seeds from your labors.

[reed]

I've been lazy on posting about my sweet potatoes but they are planted and growing. Get them in a little later than usual but that's fine. Part of the overall goal is short season maturity and eliminating need for indoor starting or artificial heat so waiting till it warms up good is part of it.

I trimmed them down to just 12 out of those I had saved to clone and have 15 large tubs each with three plants and each tub with a single type. I have them labeled to match the pictures I took when I put them in the cold frame to start the slips. I'll be able if I want to to keep seed of each one separately instead of just all mixed up as I have most often done. 

Starting them to slip in full sun in the cold frame worked great but I discovered something. Those with larger vines sprouted slips that grew up three or four inches and were easy to pull off individually. My preferred bush types sprouted bushy slips. They were only a couple inches tall and all clumped together. They were hard to separate into individual plants. I had to add a step of cutting them apart and rooting them individually. I used some cell packs full of sand set in trays of water to do that and it worked fine. A healthy stem with a nice growth tip sprouts roots literally overnight even if it is only an inch or so long.

I couldn't stand not planting any seeds so I prepped a little spot about two feet wide by ten feet long and scattered 100 seeds. That was less than a week ago and about forty of them have sprouted. It has been very hot and wet the whole time so I guess that is why so many sprouted so fast. Yesterday I also discovered a bunch of volunteers in about the same stage as those I planted. I don't know what to do with them all but I guess I'll try to scrounge up enough soil mix to fill some of the smaller pots and plant as many as I can. Also I'll just leave some in the ground where the sprouted.

That one small one with the yellow flesh has still not sprouted slips but some little purple bumps have formed so I think it might. It is the one that I accidentally ate all of the larger roots from and the one I most wanted to clone. I have a large pot saved for it and think that it can sprout slips before the first of July there will still be time to grow it out. When I put them to slip I set one side in sand and keep it wet. After pulling the others out that one ended up in a depression in the sand and was fully submerged in water for a few days by the rain. Now I wonder, if I had more fully submerged it earlier might it have sprouted sooner? Or is it because it is hotter now? Or was it just stubborn? Who the heck knows? Anyway I had pretty much given up on it but now it may be saved after all. I sure hope so as it may be the most delicious sweet potato I ever tasted.

I'm just going to plug along this year, hopefully producing a bunch of seeds from these clones. They represent the best of the best and should make a generation of seed where the chances of any particular seed producing a good plant is greatly increased.

Next year I will have to figure out what to do with those seeds and with all the older ones I have archived. I envision two large inground trials. One for this years seed and one for the older seeds.  To do them justice each will have to be a minimum of 500 sq feet, preferably 1000. Big enough to plant enough seed and allowing for low germination to end up with 100 plants in each patch and let them mature in place. Even at a 1000 sq feet each they might still be crowded but I've found they can reveal a lot about themselves even when crowded and I could cull any non-bloomers and giant vined ones along the way. Then of course there will have to be a third patch for clones as well.






 

[AndrewB]

Sounds awesome! Keep up the good work!

[reed]

Thought I would post a couple of pictures. The first one shows the difference on how a bushy one sprouts slips compared to one with longer vines.

The second one is of two of my most favored roots. Well, most favored as far as production went last year and in the case of the orange ones in flavor. I had actually not intended to keep either of these because they are not bushy but they were both very productive of somewhat spherical shaped roots and the orange one like I said is quite tasty.

The white one is also good but it isn't sweet so it isn't what I really think of as a sweet potato. It is quite good however used more like a potato, fried with onions or something like that.

Unfortunately that little very sweet yellow one decided to rot  , o'well the genetics that made it are no doubt in some of the other seeds so I can look forward to something like it showing up again sometime. If it's true that every one is genetically unique I guess it is gone for good but I'm counting on that others as good will show up.

That bushy slipped one in the picture is also very, very good and I planted a whole bunch of slips from it in the ground next to the others and also devoted one large tub to it. It also has the clump root trait as do some of the others. Will be fun in 2022 to see what comes form the 2021 seeds.

It's too wet right now to get a picture of all those seedlings nor can I explain why there are so many since some of the seeds were older. Not that germination decreases with age I don't think but because they are from older generations before much selection for easy sprouting. I guess it's cause it has been so hot an wet here.

Anyway here are the pictures. O' almost forgot, those two roots are still perfectly firm and still taste fine even after producing lots of slips. I don't recall however the others from the orange one having that whiteish coloration before.

Loos like one of the pictures uploaded twice, don't know what's up with that.

[reed]

Unfortunately I lack photo upload ability right now but thought I would post a little update anyway. With just one or two exceptions all the plants are currently getting ready to flower.

One new seedling looks to be a new super bloomer type. It is only about 6 inches tall and has more flower buds than leaves, makes me wonder if the blooming thing can go a little too far. Also seems to be a super bush type as well, just a little round clump of small leaves and bloom stems with many tightly spaced buds on each one. If it makes anything good in the root department it might be a treasure assuming it doesn't just bloom itself to death.

Over in the cowpea patch three volunteer seedlings are growing nicely. There haven't been sweet potatoes grown in that area for three years so the seeds must have laid dormant all that time. Not sure how to handle any seed that comes from these plants, might they be carrying a difficult to sprout trait? I've worked so hard to make them easier to sprout, should I even let their pollen cross back into the others? They are clear on the other side of the garden where there shouldn't be too much crossing so I think I'll just not worry about it.

Especially with one of them in particular. It has very unique looking leaves, they are green not purple but a much darker shade of green than I'm used to. Usually only the purple ones are that dark and they have much skinnier lobes on the leaves than I've ever seen, except on some I saw in a flower pot on campus of Indiana University but those were purple.

I'm thinking of dividing this project into two separate lines, one ornamental even though you could still eat the greens and one food quality. The difference being that the ornamental do not make large storage roots. That skinny leave one and this new super bloomer one might be a good place to start with the ornamental line. I've already let lots of other nice ornamentals go extinct, favoring the food ones but I have lots of old seed that I am sure would produce new ones. It's harder to keep ornamentals to clone cause you have to keep a growing plant alive through winter where you can just stick a root in a drawer and get it out the next spring.

Looking at all the bloom buds on the main food quality patch I'm pretty confident I'll get nice harvest of elite seed from them. This patch is cloned form last years best of the best and being grown much less crowded and in much better soil. I wondered if such conditions would decrease flowering but apparently not. I hope to get a nice harvest from each one, enough to allow for lots of testing in different ways in the kitchen and select down to less than ten to keep cloning.

[Richard Watson]

I couldn't stand not planting any seeds so I prepped a little spot about two feet wide by ten feet long and scattered 100 seeds. That was less than a week ago and about forty of them have sprouted.

Thats really good germination. Were they all strong seedlings?

[reed]

Yep, pretty much all of them were nice seedlings. I didn't have room so only found spots for about a dozen of them and just in time too because a rabbit got in and chomped most of the rest. I think there 8 or 10 still growing where they sprouted. I was gonna use that spot for something else but I guess they can have it at this point. Some of them are long vine types and don't show much inclination to bloom, I may cull them out so the more bushy ones can have the spot.

That one volunteer that is blooming so much is still mostly just blooming. It's leaves are sparse and small. It's a weird looking thing, hope to get back to taking pictures soon. Better be soon cause I don't see how a plant can live very long if pretty much all it has is flowers.

[reed]

Haven't updated for awhile so thought I'd post a little something. Starting to get a few seeds now, end of July, first of August. That's about in line with last few years. The seeds are harder to find than usual and some I'm sure have already been lost. Planting in better soil and less crowded has resulted in much more massive vines than I'm used to so vines and even the leaves are bigger. Although the plants are less crowded at the base they are even more overgrown than usual. I'll just keep collecting the easy to find seeds and then later on when more are maturing all at once I'll cut off a lot of the leaves to find them.

The biggest plants are those that I grew from clones but the seed started ones that were transplanted to pots are pretty big too even though they got smaller pots and lower quality soil. Most of them are are also making seeds as are about 1/2 of the ones that were just left in the ground.

Volunteers are all over the place, under tomatoes, in the cowpea patch, all over the place and although they are much smaller many of them are also blooming.  Some of these had to have laid dormant as seeds for a long time because they are just too widely scattered to be from last year's patch or even the year before.

Hope to have resolved my photo taking issue pretty soon.

O' one more thing, probably about 90% are the short vine or even the bushy variety which I prefer, yea! The biggest vines are one that was cloned from last year, it has rather spherical white / white roots. Some of those cloned this spring will probably be cloned again next year but white isn't our favorite as far as flavor so it might be dropped.

[S.Simonsen]

I finally got my first in-ground trial of the seedy sweet potato line completed. I grew about 14 seedlings out, kept in pots for safe keeping, and planted out slips into a bed. I improved the texture of our cracking clay by digging biochar into a one spade wide/deep channel where the slips were planted. They were top dressed with a little goat and chicken manure. We had a strangely cool/wet summer as they grew. I harvested the roots after a little over 6 months growing.

During the growing season I was impressed at the diversity and compactness of the top growth. Flowering started at around 3-4 months, and I managed to collect a small amount of seed but a lot of it wasn't well formed (still soft inside a dried capsule). It seemed to take our local pollinators a while to figure out the patch. The cold summer might have contributed to slow seed formation. One clone with huge orange roots that pushed out of the soil didnt flower. I took slips from each clone to pot up again. The original pots got hit by rats as they tubered up.

When I dug all the roots I was again impressed, overall. Some varieties had very small roots, some rotted, some split, some divided into chains of tubers. But about 1/3 of the varieties had large, smooth roots produced in clusters of 4-8 right at the base of the plant. The varieties with a slightly rough skin seemed to hold up to our bandicoots, which had been digging up our high cyanide cassava tubers for months before moving onto the sweet potato. I am hopeful there may be some potential to breed at least moderate bandicoot resistance into my sweet potato line. I plan to grow at least twice as much in field trials next year, one bed with each clone for pollination/diversity, and another bed or two with only the best quality tuber clones for production (and seed formation, using the pollen from the other clones if needed). Once I have a healthier size seed stock in long term storage I will try only growing the handful of best clones along with their outcrossed seeds to start improving average tuber quality. A hotter summer might help seed set, or simply turning over a few generations.

All in all I am very happy. I had nearly given up on sweet potato. I did see a tiny touch of tuber weevil in some of them, but being able to eliminate all the vines every year and restart from seed gives me hope I can come up with ways to manage this serious pest. Big thanks to Reed and the others that started and shared this project.

Going forward I am curious to see if I can turn sweet potato into an annual starch crop. Grafting seedlings temporarily with more toxic/pest resistant members of the family might be a way to transfer some microbiome that makes them less palatable as whole tubers. That would work for me as I want a root crop I can grind up and store long term as starch, like arrowroot, cassava and typha.

[reed]

I had a couple show up last year with very rough skin, I almost culled them but they were such good seeders I decided to clone them this spring but I only planted one of each. Just couldn't bring myself to discard that super seedy genetics. One is orange and very sweet but they about have to be peeled before cooking cause the skin is so rough it's about impossible to get them clean otherwise. The other is white and not sweet at all.

I don't know much about growing for starch, I'm guessing for that, you do not what them to be sweet? My preference is the opposite of that and find the orange and especially the yellow ones are the sweetest. There is a variety here called O'Henry that is white and described as sweet but none of the white ones I've encountered were sweet. I've never grown O'Henry.

[S.Simonsen]

Colour and sweetness might correlate in terms of sugar/starch, but I have read the beta-carotene in vegetables gives them a pleasant taste as well. That rough skinned super seedy form sounds amazing- any chance I can get some seeds from it? It is amazing how seemingly minor and possible negative traits in one situation can turn out to be the key for success in a different location.