On the potato pages describing crosses, where it says berry set, seed set, germ. Germ is either yes or blank. I assume blank means no germination? But maybe it means they didn’t try to germinate the seed, although that seems unlikely.
The reference papers don’t always report on germination. If there is no info in the paper, there is no info in the summary. In some cases, particularly in the major reference works, crossing was done primarily to evaluate whether or not species were closely related, not to actually grow the seeds. My guess is that somebody did try to grow a lot of those seeds, but it may not have been deemed important enough to publish on its own.
That makes sense. I was thinking about trying to cross commersonii and jamesii, just to play around. Maybe look for some palatable ones with decent size for a wild type. Short stolons on the other hand seems like a more challenging trait to select for in wild species. Speaking of short stolons, in Twanoh, is the hypothesis now that the short stolons came from tuberosum genes instead of just from polyploidization of acroscopicum? I was surprised to see on the commersonii page that you can cross commersonii with tuberosum.
Several papers have reported crosses between commersonii and tuberosum, but I think we’re talking about very small numbers of seeds. Crossing diploid commersonii with diploid tuberosum will give triploids due to the mismatch in EBN.
In Twanoh, I’d bet that the short stolons came from Tuberosum, but it is all pretty speculative.
I thought commersonii and jamesii diploids are both 1EBN?
Sorry about that, I meant tuberosum. Commersonii/jamesii crosses should produce normal diploids, although I don’t think they cross very easily.
1EBN group seems to have the potential for a fun experimental project. Going to get some material from Cultivariable and play with it.
That’s interesting to that 1EBN diploid x 2EBN diploid gives you a triploid. I will have to read more to understand it. What about those verrucosum bridge crosses then, I saw that GRIN has one with cardiophyllum and one with commersonii—are those triploid?
To cross 1EBN and 2EBN diploids, you pollinate the 2EBN species with the 1EBN species. You are counting on the 1EBN species to produce some unreduced pollen, which will be effectively 2x, 2EBN. When you combine that with the normal (reduced) 1x, 2EBN gamete from the 2EBN species, you get a 3x, 2EBN zygote. Unreduced gametes are produced in low frequencies, so you will typically get few seeds from different EBN crosses.
I haven’t looked at the verrucosum bridge crosses in depth, because I think most of them are male sterile. They are more a step toward moving 1EBN genetics into tuberosum. A purely 1EBN breeding pool seems more likely to maintain fertility.
I have been doing the verrucosum bride crosses! Chance mentioned the verrucosum bridge crosses on GRIN I have done tons of pollinations with those and they aren’t extremely fertile but you can make crosses with them at the diploid level to get diploid progeny. The clones available on GRIN are from Shelley Jansky in Wisconsin who just recently retired (and they are diploid), but she has published two papers on the subject that are a must read if anyone wants to attempt this.
I will say that this is an extremely difficult, technical, and time consuming process and most amateur growers would never see much success. As Bill has said the fertility is really poor when you try and bridge the 1EBN species into the 2EBN species, and the direction of the cross matters a lot. That being said I have managed to introduce genetics from commersonii and cardiophyllum and a couple others into tuberosum using this method.