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

[AndrewB]

From what I've seen if you grow sweet potatoes in water they don't make any storage roots at all, even if it's one that does make roots when grown in soil. They do bloom and make seeds though. I don't know if this might be a way to induce blooming or not but if you like the greens it is definitely a way to produce them in abundance and the fish in a small artificial pond really enjoy it too. Some kind of bugs hide, or may just tasty algae grows in those root mats and the little bluegills are always looking around in them. Or maybe they just like hiding in them too.

So, could hydroponically grown slips be a viable alternative to bulking up seed?

If that's the case, maybe I could get some slips from you guys who have reliable seed setting varieties,  but not enough seed to share. Or I could attempt it on my own. Are the ornamental varieties better at seed set? Is there better seed set with different varieties vs selfed?

I only check this thread occasionally,  so I'm not sure what the state of this project is at this point in time. How are you all getting along with it?

[reed]

So, could hydroponically grown slips be a viable alternative to bulking up seed?

It's easy to make slips from any growing vine. It could be in an actual hydroponic system or just a glass of water on a windowsill or growing in the ground or pot in a greenhouse. Any section of vine at least a couple inches long with a leaf joint will root and in a little wile be big enough to make still more slips from it. And by then you can get more from the older one.  It isn't a substitute for seeds though cause it still requires keeping either a plant or roots alive during the off season. 

If that's the case, maybe I could get some slips from you guys who have reliable seed setting varieties,  but not enough seed to share. Or I could attempt it on my own. Are the ornamental varieties better at seed set? Is there better seed set with different varieties vs selfed?

I don't really make the distinction between ornamental and culinary anymore. All it means is if they make useable sized storage roots or not and that I think is just another variable trait in the species. I do think my initial luck in the project was because of the chance discovery of a self fertile "ornamental" and that trait got passed into my overall grex but most existing varieties are not self fertile. I don't really know the percentage of mine that are because I grow them all in a polyculture.

I only check this thread occasionally,  so I'm not sure what the state of this project is at this point in time. How are you all getting along with it?

Currently the "turning sweet potatoes into a seed grown annual" project is largely complete. This year I planted seeds directly in the ground and had about 30% germination within a couple of weeks. That was enough and fast enough to more than fill my planting area. Many that didn't come up fast enough were just left crowded in the planting bed, some ended up blooming but most came up too late to make much roots. A smaller number planted at the same time in a cold frame had about 70% germination in time to plant out but I didn't have enough space and favored the direct planted ones.

There are still lots of questions I'd like to answer but not likely to be able to, especially concerning compatibility. Who is self fertile and why? Who is compatible with one or more particular other and not another and why? Who is compatible with one or more other but only in one direction?  Are there any that are compatible with most or all others? Are self fertile ones compatible with others as a rule or are most of their seeds selfed? And lots of others like how are traits passed on?

I doubt I will ever know those answers cause it is just way more than I could do to answer them and the university scientists don't seem to care or if they do they don't seem to write about it. They just do large scale polycross looking for the next one to patent as a clone. They don't care about garden scale growing from seed. 

From what I read pretty much all traits are quantitive so I have just been applying what I call genetic distillation, trying to  cull out those that don't make nice roots, that have giant vines, don't bloom well or don't taste good. Stuff I can do just by looking and tasting, no need for microscopes, DNA tests and mountains of records.

This year I ended up with about 20 that meet most or all of my favored criteria. I archived most of my seeds in sealed test tubes, inside stainless steel canisters buried in the ground. Next year I'm planning on growing mostly just clones of those 20 with hope to make a new elite line of seeds.

State of the seeds right now is roughly. A single seed has about a 30% chance of sprouting within two weeks planted directly in the ground. That plant has probably a 95% chance that it will bloom and set seed, assuming it has an appropriate partner or is self fruitful. It has about a 70% chance that it will make nice roots and seeds within 100 days of sprouting. Probably 70% chance it will have bushy rather than large vine growth habit. I won't venture a guess on lots of other things like color, flavor and so on.

I am hopeful that the seeds produced next year will reveal all kinds of wonder things in 2022. Also I'm making more effort next year to give them better soil and take better care of them so as to learn their real potential as far as yield. If any of of those 20 show superior there I might also clone them again in 2022.

"What a long strange trip it's been"

[Richard Watson]

Its great that you are getting around 70% chance of being the bushy type, to have trait that and to also have tubers close to main stem is the way to go.

[reed]

Its great that you are getting around 70% chance of being the bushy type, to have trait that and to also have tubers close to main stem is the way to go.

I forgot to mention that but fortunately the two seem to go together to some degree. Between them though the clump root trait is the most important to me. It's a lot easier to trim or trellis big vines than to dig giant craters at harvest. It's even easier when growing in the big tubs, sometimes I can just loosen the dirt with my fingers and pull an entire clump root plant out in tact but still have to dump the tub to find the others.

Sometimes in the small pots and once in a while even in the big tubs I've found no roots at all inside. The big ones grew deeper, off of the feeder roots that had exited the drain holes. At first I kept all that bloomed but I've been culling those kind for last three or so years. Also cull the ones that make giant roots.

My tubs are maybe 50 centimeters deep, they are old juice barrels that the local winery gave me cut in half. Some have plugs on top about 5 centimeters across that become drain holes. One time I couldn't tip one over to harvest, it just wouldn't budge. When it finally broke I found a giant sweet potato had formed in that hole, 1/2 inside and 1/2 underneath, each piece weighted about 500 grams. I remember that plant had bloomed and set seed but I sure didn't keep it to clone. (hope I got my metric conversion right)

[nathanp]

From what I could tell from my TSPS plants this year, the main difference between bushy and non-bushy (vining) plants seemed to be length of the internodes.  Bushy types have short internodes, and vining types have longer internodes. Michael Jennings confirmed that seemed to be the case after also looking at his plants. 

It could be that trait also corresponds to location of storage roots being either close together for bushy plants, and further apart for vining.  I was wondering if this was a trait that also was quantitative, and whether it isn't an either/or trait, but something that has a broad range of intermediate stem lengths.  I did not have enough plants to determine that, but it seemed likely given so many other traits are quantitative.

If that is the case, it seems likely you could select for extreme bushy types with very short internode lengths and possibly eliminate the longer internode lengths from your genepool.

[reed]

Yes the bushy ones do have shorter internodes, they also tend to have flowers in clusters where longer vines often have just one or two flowers per stem. The longer vines that do bloom however tend to do it at virtually every internode and have a higher percentage with a full four seeds per capsule. But, yes I do believe the trait is quantitative, they can have from one to as many as twenty flowers per stem.

I think I fell into the bushy ones by the same accident as the seedy ones and I do like them best but can't completely discard the others yet. A lot of them are good or very good, probably not more than 20% since the beginning (of those that made nice roots) were really bad, flavor or texture or bug prone or whatever.

The best one ever so far and maybe the best sweet potato I ever ate showed up this year in the purple skin, yellow flesh one but it isn't bushy. It isn't a giant, only four feet or so but definitely not bushy and it has the two or three flower per node habit. Makes less seed per plant than a bushy but all are excellent quality fully formed seeds.  I'm gonna clone the heck out of it next year so my bushy preference may take a set back.

The UNC, I've read starts as many as 50,000 seeds per year but have only released one new one that I know of in the last ten years or more. That has me puzzled as it seem to me fairly easy to find really good new ones. I guess they have different priority like maybe tough skins, some and that wonderful purple/yellow one is like that, before curing you can rub the skin off with your finger, it would never survive mechanical harvest. And they know a lot more about other qualities than I do but I suspect it mostly has to do with commercial production than flavor.  I guess they also aren't interested in seeds on a patented clone or seed to harvest in 100 days but still with 50,000 a year they have to have culled out, by my standards,  some really great ones along the way.

[S.Simonsen]

Selection for compatibility with mechanisation is one of the great tragedies of modern plant breeding. It overrides everything else unless it is a crop with a high enough profit margin and suitable pool of slaves (virtual or actual) to do the manual harvesting (coffee and chocolate are great examples). Uniformity is the biggest factor since most farm machinery cannot tolerate much of a range in size of the plant organs or the timing of harvest.

[nathanp]

The UNC, I've read starts as many as 50,000 seeds per year but have only released one new one that I know of in the last ten years or more. That has me puzzled as it seem to me fairly easy to find really good new ones. I guess they have different priority like maybe tough skins, some and that wonderful purple/yellow one is like that, before curing you can rub the skin off with your finger, it would never survive mechanical harvest. And they know a lot more about other qualities than I do but I suspect it mostly has to do with commercial production than flavor.  I guess they also aren't interested in seeds on a patented clone or seed to harvest in 100 days but still with 50,000 a year they have to have culled out, by my standards,  some really great ones along the way.

i am sure they are thinking only of commercial grower's interests.  This is the same with solanum potatoes.  Breeding programs will often grow out 100,000 seedlings for each one they eventually select.  Mechanized harvesting would be one of them, as Shane mentions, but so are many other traits including dormancy, regular shapes, consistent yield, disease resistance, etc.  Commercial potato programs have a list of over 30 traits that they are evaluating for, and evaluation can take 7-14 year for each new variety before they normally would be released.  So the vast majority of seedlings are eventually discarded.  I do not know how long the list is for sweet potatoes, but I would guess it is close to as long.

[S.Simonsen]

A lot of it comes down to marketing as well. Most consumers are very reluctant to try something different, even a new variety of apple with a slightly different colour, sugar/acid balance and mouth feel with often fail spectacularly despite being a great product simply because people tend to stick with what they know. Introducing a new variety means committing to a huge investment to sustain the push to gain market share, and the real risk of it not working out. We recently had "low carb" potatoes turn up in the shops with a bit of fanfare. They were still a non-waxy type, but instead of being starchy were just kind of bleh and nothing, vaguely crunchy even after cooking in a way I have never seen in a potato before . I figure some marketing genuis was convinced all the paleo people and weight watchers would jump on it. Haven't seen them in a couple of years now so I don't think it worked out.

[reed]

I never used to even like sweet potatoes. Everyone I know and I think most people in general cook them covered in butter and brown sugar or maybe honey and they cook them into a mush with the consistency of baby food. Sometimes they stir in some marshmallows and call it a casserole, its gross. I guess if that's what your after anything that's the right color and shape works.

Most of mine still need a little assist from the butter and honey and I don't eat much of them. But there are others that are fantastic just baked dry and eaten that way. And there are some that aren't sweet at all and are good fried like potatoes with onions or in soup or beef stew, they have a different texture and cook faster than potatoes.  Eventually I'd like to separate the sweet and non-sweet into isolated breeding groups.

I would like to select for disease tolerance but haven't encountered much of that. There have been issues with those wire worms or I guess that's what they are but only in the solid purple ones that show up once in a while, I don't keep them. And there are definitely differences in how much Japanese beetles like them, I have had an occasional plant completely eaten by them when others were barely touched.

I've primarily selected for seediness, then for nice sized storage root over stringy roots. Then I guess for bushy habit and what I call clump root where a nice cluster of roots is right under the main stem. I've selected a little for long storage just by not cloning any that wrinkled up or otherwise didn't look good when time to make slips. And I favor fast maturity, in range of 100 days from seed.

All the different flavors and color combinations mostly just show up unpredictably but it makes it fun at harvest time to see what I get. The wonderful purple/yellow ones just showed up this year. By cloning this year's best ones and not starting many new seeds next year will be the first time I've really tired to focus on culinary qualities.

[add] By the university's standards a good one must show up about 1 in a 100,000. Seems like I even read that somewhere. Its a very discouraging statistic, makes one think breeding on a small scale isn't worth the trouble. But it is that standard that makes the difference I guess. For commercial/industrial production it has to withstand planting, tending, harvesting, washing, sorting, shipping by machines. If it also tastes good that's a bonus I guess but not really necessary and not at all necessary for it to make seeds.

You hear the same type thing about any plant that is traditionally sold as clones. Grapes and apples come to mind, sure they say, "you can plant the seeds but what you get won't be any good". I don't think they are really trying to mislead or discourage, it's just not how they think to consider some people don't care about industrial production.

[Lauren]

I guess that makes sense, but how did that attitude (that nothing is good unless it's cloned) pop up in the first place? Up until the 1940's seed grown trees were common. People bred their own, they couldn't afford to buy a clone from a nursery. So at some point did some breeder think, "Darn, these people who grow their own are cutting into my profit margins"?

I have a seed grown interlaken/concord cross grapevine. The taste of the concord with the sweetness of the interlaken, the white skin of the interlaken, and it ripens just a few weeks later than the interlaken, so late July early August. I see no negatives here. But I've had people tell me flat out that it can't give good fruit--until they taste it.

Why do people just one or two generations removed from the reality actually believe that what their ancestors did as a standard is impossible?

[reed]

It's a little later than I ordinarily do it but will be starting a few seeds soon and also cloning those best ones from last year. I have about 25 roots from last year, each one grown from a seed. I was intending to grow a tub of each one but I'm thinking of trimming that down by about half based on how well they stored and how easily they sprout slips.

I can't bring myself not to start any from seeds but will probably not plant more than 25 or so and I'm doing the whole operation outside in the cold frame, even the slips. Part of my overall goal is select them to be no more difficult to grow either by seed or clone than a tomato is, and part of that is no indoors or artificial light aspect too it at all. I've been reading more about them and although I'm sure season length has some importance what they really need is heat units so there is no need to start them sooner than the heat is expected to arrive.

I have cloned lots of my seed grown plants over the years, mostly with the intention of reinforcing the seedy trait, the bushy trait and the clump root trait but always let any particular one go extinct after just a season or two. Well, of course I have also selected for usable sized and tasty roots along with the other traits.

It is certainly possible to arrive at any one of those traits, probably all four in the same plant and perpetuate it long term IF on going cloning is used. To perpetuate it indefinitely by seed each year is probably not as easy.

Still, I have succeeded in making sweet potatoes into a seed grown annual so now I want to make them into a seed grown annual where the chances of any particular seed producing a plant with the desirable traits significantly higher than 50%.

Since I can't expect all four traits to show up reliably in any one plant I guess I need to assign a priority of traits:
1- blooms and matures seeds
2- produces quality food grade roots
3- clump root development
4- bushy growth habit

There are of course several other traits to keep in mind like storability, ease of sprouting slips and lots of others but for now I'm mostly gonna focus on just those four starting, except for what few seeds I do sprout, with just clones of my best plants from last year. 

[nathanp]

[add] By the university's standards a good one must show up about 1 in a 100,000. Seems like I even read that somewhere. Its a very discouraging statistic, makes one think breeding on a small scale isn't worth the trouble. But it is that standard that makes the difference I guess. For commercial/industrial production it has to withstand planting, tending, harvesting, washing, sorting, shipping by machines. If it also tastes good that's a bonus I guess but not really necessary and not at all necessary for it to make seeds.

While the 1 in 100,000 statistic is true of Solanum potatoes, I strongly suspect that is not true of Sweet Potatoes.  If you watch the video with Craig Yencho talking about his program, he gives much lower statistics from what can recall.

They are just looking at many more traits than we might, including things like how easy is it to harvest mechanically with machines,  and how uniform the tuber placement is.  Commercial Solanum potatoes are bred and evaluated on more then 30 traits.  I find a much higher percentage of potatoes from true seed that I find useful and worth regrowing.  Even if it is in the 2-5% ballpark, that is much higher, and sometimes as high as 80% of tubers from seed will produce offspring worth evaluating. 

[S.Simonsen]

Hey Reed.
Great to hear how your project is progressing. I have my first big in ground trial of seedlings from your line progressing nicely. I will dig in a month or two (I am guessing 6 months to maturity is about ideal?) and then clone the ones with the best roots. Interestingly despite flowering heavily here there is no evidence of natural seed set, which is weird since our wild Ipomoea are covered in carpenter bees. Maybe they haven't noticed the sweet potato patch yet. I will do hand pollination next season once I have weeded out any clones with substandard roots first. I am seeing nice compactness in the plants above ground so far as well in many of the seedlings- a really lovely trait that makes managing the crop much easier. Thanks again for doing the speculative work way back at the beginning to restore fertility to this important crop.

[reed]

Yea, the 1 in a 100,000 thing is just goofy, even in the very early stages when they were only a generation or two removed from the rootless ornamentals a nicely rooted one was never less that 1 in 10. Of course that is based mostly on root size, not other factors like flavor or growth type.

The university select for all kinds of things that are beyond my ability even if I wanted to. I think they measure sugar content, select for disease and insect resistance, lots of stuff that could only be done with very large scale grow outs, testing and recording. They even breed for specific color after being fried like French fries or chips. For a home gardener like me all those things are certainly important but I think being able to sustain ongoing crops without need of preserving live plants in the off season override it all. Once you get the seedy ones you get lots of seeds and your next year is insured no matter what happens to your saved roots or houseplants. Not to mention since the greens are also food there is in a sense no such thing as a bad sweet potato.

S. Simonsen, I would never have believed that insects had to learn to like a particular flower but it might be true. In the first years I had flowers on mine pretty much nobody was interested in them. The bumblebees caught on first and sweet potatoes are now about the first flowers they visit each morning. In last couple years a lot of smaller bees and even hummingbirds have joined the party. Still though I have never seen a honeybee on a sweet potato flower.
Hope not, but it is also possible yours are not self or cross compatible. That's another little issue that I'm afraid could be a problem in future generations.