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Post by raymondo on Mar 24, 2015 19:17:14 GMT -5
I'm wondering whether it's worth trying to restore fertility to potato cultivars that produce flowers but no berries or produce both flowers and berries but no seeds. There are no doubt a variety of reasons why many, if not most modern cultivars are sterile. I'm not sure what they are though. Just from observation, lack of pollen seems highly likely in those I've looked at. I have so far collected three fertile cultivars - Desiree, which supposedly produces pollen but is self-infertile, Pentland Dell and Pink Fir Apple. A popular garden cultivar here is Sebago which produces copious quantities of seedless berries. I'm hoping that crossing it with a fertile cultivar will produce some fertile offspring.
Basically, I want to grow potatoes that are fertile. Self-fertile would be ideal but just plain fertile will do. I also want deep colours - purples, reds, yellows. I have a deep purple one, grown from seed sent to me, some of which have themselves set seed so that's a good start. I don't know how it set seed though because for the life of me I cannot find any trace of pollen! Do potatoes exhibit apomixis (asexual seed formation)?
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Post by templeton on Mar 25, 2015 2:53:33 GMT -5
Ray,
I got seeds off a Pinkeye, which were fertile - it might have crossed with one of the feral spuds in the garden. I think that is what i sent you a while ago.
I think Purple Congo might set seed, as well.
If you outcross to restore fertility, will the other characteristics remain? Or will a back cross work? nice problems!
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Post by nicollas on Mar 25, 2015 3:52:58 GMT -5
What i've read several times is that it is far easier to start with TPS and then cross/select than to bother to try to make seeds from unwilling plants
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Post by philagardener on Mar 25, 2015 6:05:37 GMT -5
Sebago is from a cross of Chippewa x Katahadin. The Chippewa and Katahadin parents were sibs; all the breeding and selection was done by the USDA in Maine (USA) looking for productivity and disease resistance. archive.org/details/katahdinchippewa276clar . It sounds like there was a fair amount of genetic variation in that F1. Katahadin produced OP seed in my garden, but I grew several varieties in close proximity and pooled the seed; don't know what was selfed and what was outcrossed. Chippewa (which I have not grown) was reported to be a poor seed setter like its offspring Sebago. Because of that, a backcross to Katahadin (which apparently is grown in Australia) might be the best bet to up fertility and retain the desirable characteristics of the line. On the other hand, if Sebago has viable pollen, outcrossing to a different female parent might restore fertility more quickly. Sounds like a fun project! |
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Post by oxbowfarm on Mar 25, 2015 7:33:38 GMT -5
Rebsie's book is worth reading on this topic, also Raoul A. Robinson's Potato Breeder's Manual. My basic understanding is that for cultivars with poor fertility and male sterility, berry production is possible if you influence the plant to prevent it from aborting the fertilized ovaries/berries. Robinson like to do this by grafting onto tomato rootstocks. David Holm at the CSU potato breeding program has stated that they do it quite easily in pots in their breeding greenhouse. So potted plants might work. You'd still need a pollen donor for male sterile cultivars, and a lot of potato cultivars are male sterile.
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Post by nathanp on Mar 25, 2015 10:59:27 GMT -5
Tetraploids are capable of being self-fertile as long as they are not male sterile. Nearly all commercial potato varieties are tetraploid.
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Post by oxbowfarm on Mar 25, 2015 13:13:36 GMT -5
I think fertility in potatoes is always going to be hit and miss if you are growing them anywhere with a non-Andean equatorial climate. I've grown a pretty extensive selection of weird potatoes for the last few years, much of it descended from Tom Wagner's breeding work via Doug Strong. So there is plenty of pollen flying around my potato patch, but some varieties will produce berries some years and not others. But if you have male fertile cultivars you always end up getting some berries to work with. I remember when I gardened in Colorado, I had good berry production from very standard commercial varieties, so cool summers at high altitude may be enough sometimes. My summers are nothing like that here, but I have much more naturally fertile cultivars to work with now.
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Post by DarJones on Mar 26, 2015 2:48:48 GMT -5
Some potatoes are parthenocarpic, they produce berries but few or no seed. I have not yet seen a way to use parthenocarpic in producing TPS, but it is possibly useful in extreme climates. Parthenocarpic tomatoes are highly useful in cool maritime climates because edible fruit is produced even if no pollination occurs.
Some potatoes are self-infertile, usually because they carry a version of the "s" gene which prevents self pollination. This is complicated in tetraploids because there may be 2 variants of the "s" gene in the mix which severely limits the potential to set fruit.
Some potatoes are pollen sterile, the flower is otherwise healthy, but the pore is closed or the anther is defective. The end result is a plant that does not make pollen. Tetraploids tend to be pollen sterile, probably as a result of the chromosome arrangement.
Varying combinations of the above are common. Self-infertile and pollen sterile varieties are typical of S. Tuberosum. While a plant may not produce pollen, it may still be difficult to produce seed when pollen is brought from another variety and applied to the flowers. This is because the plant does not produce pollen and multiple other varieties happen to have incompatible "s" genes.
The easiest one to deal with is potatoes - mostly commercial varieties - that set a huge load of spuds which act as a photosynthate sink absorbing all the energy and nutrients the plant produces. This prevents berry set because there are not enough resources to go around. Azul Toro is a good example. The way to get these varieties to produce seed is to change the load balance. Plant these potatoes a few weeks later than normal and push them just barely into the surface of the soil. The resulting plants won't have room to make stolons and therefore will have extra resources to devote to producing seed. I accidentally stumbled on this method a few years ago and have used it several times since.
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Post by templeton on Mar 26, 2015 19:18:58 GMT -5
The easiest one to deal with is potatoes - mostly commercial varieties - that set a huge load of spuds which act as a photosynthate sink absorbing all the energy and nutrients the plant produces. This prevents berry set because there are not enough resources to go around. Azul Toro is a good example. The way to get these varieties to produce seed is to change the load balance. Plant these potatoes a few weeks later than normal and push them just barely into the surface of the soil. The resulting plants won't have room to make stolons and therefore will have extra resources to devote to producing seed. I accidentally stumbled on this method a few years ago and have used it several times since. very fortuitous. Do you think a similar mechanism is working on cross-species grafting? denial of tuber formation, with consequent flowering? T |
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Post by darrenabbey on Mar 26, 2015 22:14:49 GMT -5
The easiest one to deal with is potatoes - mostly commercial varieties - that set a huge load of spuds which act as a photosynthate sink absorbing all the energy and nutrients the plant produces. This prevents berry set because there are not enough resources to go around. Azul Toro is a good example. The way to get these varieties to produce seed is to change the load balance. Plant these potatoes a few weeks later than normal and push them just barely into the surface of the soil. The resulting plants won't have room to make stolons and therefore will have extra resources to devote to producing seed. I accidentally stumbled on this method a few years ago and have used it several times since. very fortuitous. Do you think a similar mechanism is working on cross-species grafting? denial of tuber formation, with consequent flowering? T Definitely. The same idea also seems to be at play in other scenarios, like the production of true seed in garlic. |
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Post by raymondo on Mar 30, 2015 3:48:20 GMT -5
The easiest one to deal with is potatoes - mostly commercial varieties - that set a huge load of spuds which act as a photosynthate sink absorbing all the energy and nutrients the plant produces. This prevents berry set because there are not enough resources to go around. Azul Toro is a good example. The way to get these varieties to produce seed is to change the load balance. Plant these potatoes a few weeks later than normal and push them just barely into the surface of the soil. The resulting plants won't have room to make stolons and therefore will have extra resources to devote to producing seed. I accidentally stumbled on this method a few years ago and have used it several times since. This probably explains why I found seeds in berries produced by potatoes that were in my garden when I bought the place. They were growing right at the surface, slightly protruding in fact. This may also be why the plants I grew from seed have themselves set seed. They, too, are growing right at the surface. |
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Post by nathanp on Mar 30, 2015 21:10:53 GMT -5
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Post by philagardener on Mar 31, 2015 17:43:41 GMT -5
Kind of reminds me of when the kid try to balance eggs on the sidewalks on the equinox! :>)
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Post by trixtrax on Apr 6, 2015 1:51:00 GMT -5
raymondo It is actually quite easy to achieve copious amounts of fertile seed-bearing fruits when starting with a population of diverse TPS. Commercial varieties are tetraploids almost exclusively and as such are going to mostly be inbreeding without intervention, so hand pollinations at first between all the diversity you can get your hands on will help create a nice population to select for fertility. For the most part, fertility seems to quickly restore. You can skip ahead using fertile TPS and crossing those clones to the standard commercial varieties. Some infertility is due to outlier species used in breeding which create incompatibilities/weak pollen while other infertility can be generated from repeated inbreeding which is common in fine-tuning a commercial variety. One reason infertility is selected for is that most commercial farmers don't want copious TPS seedlings the next year coming up where they had their taters. ;p One interesting thing I have noted, is that even heavy berry set does not *seem* to interfere with a nice potato yield. Infertility is also often caused by climatic conditions. Excessive heat will abort flowers around or above 29.5C (85F). Keep your potato rows reasonably moist especially using driplines. Try planting early to get flowers in cooler temps, if possible, or try shade cloth. Also, potatoes prefer a slightly acidic soil which will help promote flowering. Nutrients should be in the NPK ratio 2:3:4 with access to plenty of micronutrients especially a bit of chlorine. Seaweed meal is a great stimulant for potatoes and a good source of Cl amongst other micronutrients of course. They love foliar-fed fish spray. Keeping them pampered seems to help push out the fruits. Bumblebees here seem to be a major pollinator so attracting them to your site with native species they prefer helps. Many of the best colored tetraploid potatoes commonly available are either PVP or licensed in some way, unfortunately. As for diploids, they out-cross almost exclusively. There are a number of species in the main petota complex that all freely cross amongst each other for the most part. USDA GRIN probably ships to AU and would be a good source of breeding material. www.ars-grin.gov/nr6/If you use Facebook, I recommend checking out the group 'Kenosha Potato Project', 'Radix Root Crops', and 'Plant Breeding For Permaculture' where we talk about this stuff all the time. Also, Tom Wagner's forum is a good starting place for this kind of stuff which has many suggestions on good varieties to try, particularly out of the USDA GRIN repository... tatermater.proboards.com Potatoes do not exhibit apomixis. oxbowfarm is right that top grafting potato vines onto tomato rootstock will often provoke a potato variety to produce berries especially if hand-pollinated. I don't have firsthand experience with this though, but I know that Tom and others have done this with success. Should be able to work in a nursery pot big enough to create tomato fruits, given good fertility, here we'd use a 1 gal pot or 2 gal pot. DarJones Nice idea about planting the tubers shallow, I'll give that a spin this year.  templeton The top-grafting induces more flowering hormones in the potato vine.
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Post by philagardener on Apr 6, 2015 19:05:54 GMT -5
Commercial varieties are tetraploids almost exclusively and as such are going to mostly be inbreeding without intervention . . . As for diploids, they out-cross almost exclusively . . . I'm intrigued by this, trixtrax . Any idea how, if those tetraploids came from doubling diploid strains, extra copies of the same self-incompatibility alleles let the tetraploid be self-fertile? |
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