Breeding Sweet Potato in Europe

[reed]

No, I don't do anything to induce flowering or sprouting. No grafting, no chemical stratification, no nicking the seed coat. I started with the accidental discovery of some seeds on a self-compatible ornamental variety. I think in the first year I only had three seeds sprout and only two survived, but I was able to cross them to some old heirloom varieties. Ten years on, I now have them coming up volunteer from seeds lost in the garden. Last few years I've been saving and cloning the best of the best and backcrossing to newly sprouted ones. I'm trying to turn them into a seed grown annual rather than finding new ones to clone indefinitely.

This is a rough guess, but I now have it to where any particular seed has about a 50% chance of showing all of the traits I'm selecting for.

Those traits being:
*Easily flowers and matures seed
*Bushy growth habit
*Produces nice sized roots in a clump, directly under the main stem
*Produces harvest (from seed) in 100 days or less

Most seeds now have a near 100% chance of having at least a couple of those traits, but other undesirable traits still show up as well.  Only those that have all the good traits and none of the bad are cloned to backcross the next year.

[Angelo Dewitte]

We do graft because most of the varieties do not flower spontaneously outside during their growth season (end may-begin october).
We have some exceptions such as purple 1 and our selection 19008; they flower abundantly from august on without grafting.
However, after grafting, we've managed to induce flowers in most of the varieties.
-Some varieties produce many flowers and seeds such as Bayou Belle, Bellevue, ... and also the varieties that flowers spontaneously
-Other varieties produce rather a low amount of flowers such as beauregard
-On some varieties (such as tainung) we were not able to induce flowers, even after grafting.
Maybe with other rootstocks? We tested a few rootstocks and had the impression that star of yelta was the best one. Star of yelta seeds are easy to obtain. Once you have seeds, you can easily grow your own plants and harvest 100s seeds from one plant. It is also a very nice ornamental.
Unfortunately, the ability to flower is not inherited in the seedlings, we have to graft again (except for some seedlings like our 19008).

The outcome of grafting is also very different. If you make 10 grafts with the same variety (eg. beauregard), 5 of them may flower, while the others do not. I have the impressions that plants that start to grow quickly after grafting, mainly grow vegetatively; while slow starting grafts flower more abundant.

@Reed: So your aim is rather to turn them into annuals. What a nice idea! But I can imagine it is difficult. They are hexaploids. I have experience with chrysanthemums, which are also hexaploids. There is an enormous segregation in characteristics and you need some generations of backcrosses to obtain some 'predictable' seeds with many of the desired characteristics. Furthermore, it's time consuming to obtain large amount of seeds, it's not like tomato...
Keep me informed about your progress!

[reed]

@Reed: So your aim is rather to turn them into annuals. What a nice idea! But I can imagine it is difficult. They are hexaploids. I have experience with chrysanthemums, which are also hexaploids. There is an enormous segregation in characteristics and you need some generations of backcrosses to obtain some 'predictable' seeds with many of the desired characteristics. Furthermore, it's time consuming to obtain large amount of seeds, it's not like tomato...
Keep me informed about your progress!

Yes, while it's fine to save some roots to clone each year, I want to eliminate the necessity of it. My biggest obstacle to reaching the goal more quickly is space, I just can't grow large enough numbers of plants each year.

Nope, they are not like tomatoes at all, you can't just squish out a few hundred seeds at a time.

That's too bad the flowering ability from grafts isn't inherited.