Potatoes: What I Have & What I'll Try


#1

Hi all. I have a similar thread on another forum, but I figure I’d post here too while my berry projects go up and running. And besides, this post will be a little different.

So I’m growing several root crops right now, mostly several species of yam vines (Dioscorea), some Lerén (Calathea allouia) and one of my favorites, African “Potato” or Potato Mint (Plectranthus rotundifolius). The last one is pretty great, easy to grow and propagate, fair harvest, easy to handle, great flavor. As for the Yams, I have D. rotundata (my childhood favorite, makes for a floury mash), D. trifida (a new favorite) and “Sativa”? Air Potato (D. bulbifera, fair flavor); I’ve got a white D. alata air potato coming in the mail, as well as a deep purple Ube.

Here’s a picture of the Air Potato on the trellis (still no crop, it’s early in the year), and the mixed tub with the Lerén, D. trifida and Potato Mint.

So yeah, I’m a big fan of the starchy root crops, I plan on getting Hopniss / Potato Bean later in the year. But one crop has escaped my grasp year after year, despite my efforts… The actual potato! Whether chitted or new, the store-bought types always end up rotting in the ground. So for next year, I’ve decided to play the genetic lottery, and try my hand at growing from true potato seed. I get that potatoes don’t generally handle heat well, but I know that there are a few places in the hot lowland tropics that succeed with potatoes as a cool season crop, so I know it can be done. The question is which variety. I tried searching the internet for seed tubers of “Skagit Valley Gold” (which was recommended for Puerto Rico on the Tomatoville forum, Link One, Link Two), but I couldn’t find it no matter where I looked. So I decided to just try my hand at growing them from seed, figuring they’d be less likely to rot to death than a store-bought potato, and that I’d have a chance at getting a selection that can take my heat (if only because heat tolerant types should be the only survivors from a batch of seeds). It’s kind-of a lottery, but the odds are better, so I’m bound to win if I try enough times. I bought some Andigena seeds and some Phureja seeds (the latter should give me better odds).

Does anyone here have any experience with potatoes in hot climates? And what about selectively breeding them?


#2

Excerpt from guide:

Temperature: Tuber development declines as soil temperature rises above 20 ºC (68 ºF) and practically stops above 30 ºC (86 ºF). The number of tubers per plant is higher at low soil temperatures, while bigger but fewer
tubers are set at higher temperatures. Harvesting when tuber pulp temperature exceeds 18 ºC or soil
temperature is greater than 20 ºC (68 ºF) increases the risk of microbial rots, especially in damaged tubers.

Several factors can shift the balance between vine and tuber growth, and one of these is temperature. For the
Russet Burbank cultivar, for example, the optimum soil temperature for tuber growth is about 61°F (16°C),
while the optimum air temperature for vine growth is about 77°F (25°C). However, with a full leaf canopy
shading the soil, it’s possible to have 77°F air temperatures at the same time as 61°F soil temperatures. High
soil temperatures will delay tuber growth. A thick layer of mulch may decrease soil temperatures by 10 degrees
Tuber initiation is strongly influenced by air temperature and day length. Short days induce tuberization. Under
long days, tuberization occurs if the night air temperature is well below 68 degrees F. (20 ºC). The
temperature-sensitive parts for tuberization are the tops not the stolons. This explains why we have less tubers
set per plant when day temperatures are over 90 degrees F., and night temperatures are in the high 60′s by
mid-May, when our day length is approaching 14 hours. It is known that for every one degree F. above the
optimum air temperature for tuberization, the yield of potatoes can be lower by about 4%.


#3

Excellent detail, thanks for the information! So as I understand it, I’ll really have to start them in fall to stand a chance at getting a decent crop, and mulch them for good measure. And as for breeding them, I’ll have to select for good tuberization and strong bacterial resistance at high temperatures.

I’ve read that tps starts out dormant, and bears poor germination unless this dormancy is broken. ¿Need I store it in the refrigerator to break this dormancy, or will a year at room temperature suffice?


#4

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.