Well, I’ve taken this on as a full-blown breeding project, starting as soon as my material arrives. The TPS and tubers I ordered from Cultivariable will probably ship out next year. For the seeds, I went with the Low-dormancy Diploid mix and the Blue Flesh Tetraploid mix. For the tubers, I went with Loowit, which I think is a tetraploid-diploid cross. These will be the latter additions to the project, given the time I have to wait for them to ship out. The core of the project, on the other hand, will ship out in a few weeks time…
I made a request through the NPGS to NR6 (the Potato Germplasm Introduction Station), and they’re growing out a selection of in-vitro clones to ship as soon as they’re strong enough. I chose two Peruvian strains for their heat-tolerance: DTO-2 and DTO-28. I went with RN27.01 for some added genetic variation and for its high degree of pigmentation (referred to as super high antioxidant content). I went with Skagit Valley Gold for its disease resistance (and hopefully some heat tolerance). And finally, I went with M6 (an improved Solanum chacoense) for its heritable self-pollinating ability (unusual in a diploid), as well as for its high dry-matter content. Some time later, I came across S. cardiophyllum, a wild potato that has some edible strains and can handle heat into the 90’s as well as drought, to an extent; they’re sending me some seeds of this species, together with close relative S. ehrenbergii. This will be the founding stock of my tropical potato breeding program.
I was originally going to go with an old-fashioned quick 'n dirty method of landrace gardening: essentially a combination of natural and artificial selection from a broad genetic base (more focused on breeding out bad traits than breeding in uniformity). I would pamper my founding stock to an extent (to avoid losing it; this is not a part of the method), let them cross-pollinate freely & naturally (read: randomly), then ruthlessly plant out seedlings in the worst conditions I have (first gradually, then constantly). Those too weak to take the heat, pest and disease pressure would automatically cull themselves from the gene pool. The survivors would then have to undergo my scrutiny, culling out the least productive and lowest-quality tubers. Eventually, I’d have a strong and variable landrace of potatoes that would bear well under warm-climate conditions.
That was my initial plan. But while I still plan to go the landrace route in some plots, closer inspection of my chosen stock showed much more potential for calculated crosses. S. cardiophyllum & S. ehrenbergii (both known as Cimatli) are closely related to each other, but might have trouble breeding with domestic potatoes, and if I’m honest… I’m actually excited about the idea of domesticating another potato! An entirely separate variety, without influence from S. tuberosum. So while I will be crossing these into the main tuberosum line, I’ll also be attempting a separate breeding program for them. M6 has unsafe levels of glycoalkaloids, so I’ll keep it out of the landrace section and keep a close eye on all crosses I make with it. If the Cimatli have trouble breeding with tuberosum, I hope M6 might make a good bridge for them. Additionally, I hope to give it its own breeding program (with some influence from the other categories) to reduce its glycoalkaloid content and improve it further. The two Peruvian strains may match well together, as would either of them with the antioxidant potato and with SVG (Skagit Valley Gold). SVG should pair well with the antioxidant potato as well. These four will form the main landrace, but while I will promote random pollination, I will also attempt some controlled crosses between them as well.
And that’s the start of my breeding program. I need to figure out where to send samples of my material for glycoalkaloid testing, so I can safely share the varieties I breed. Most such compounds are bitter, but some - like tomatine - are flavorless, so they need to be tested for. For that matter, I wouldn’t mind testing the fruits as well (it’d be interesting to breed a potato that could give edible eggplant-like fruits as well). This is sure to be an interesting experiment.
And I almost forgot, before I post…
I planted out a store-bought red potato (which are said to do better here than the standard yellow ones). The yellow ones always rotted for me (even after chitting), but this one actually seems to be growing. I also planted out a blue-skinned type which is starting to burst through the soil (no picture yet though). Here’s hoping I get a half-decent crop from them.
To finish things off, a video (in spanish, naturally) of growing backyard potatoes in Puerto Rico, curtesy of the Agricultural Experimental Station in Rio Piedras.