Author Topic: Working with wild potatoes & breeding by clade  (Read 645 times)

bill

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Working with wild potatoes & breeding by clade
« on: 2018-11-03, 05:26:10 PM »
For the past few years, I have been growing every wild potato species that I could lay my hands on.  The goal of this project has primarily been to enhance my own knowledge, although I am documenting everything as I go here: Wild Potato Project.

There are three main clades of potatoes: clade 4 is S. tuberosum and its close relatives, most of which are diploid, 2EBN and A genome; clade 3 is mostly South American diploids with 2EBN and P genome, and clade 1+2 is mostly North American diploids with 1EBN and B genome.  Most breeding efforts focus on identifying resistance genes in other species and then trying to find ways to cram them into S. tuberosum.  This is often a difficult task due to ploidy and EBN barriers between the three clades, although there are polyploid species that bridge the different genomes as well.

It seems to me that there is an opportunity here for at least two more domesticated species, with one nucleus in each clade as S. tuberosum is for clade 4.  This isn't a new idea.  There has been a lot of attention in recent years on the 1EBN species, with the possibility of breeding domesticated 1EBN diploids from species like S. cardiophyllum, S. ehrenbergii, S. jamesii, and S. commersonii.  Some of these species have been used as food, including S. cardiophyllum and S. commersonii.  The tubers are small, the stolons are really long, and some have high glycoalkaloids, but there is definitely potential to select something better and these 1EBN species have a much better pool of resistance genes easily available.

The bigger surprise to me was the possibility of breeding another domesticate out of clade 3.  These South American species are probably the most poorly known of all the wild potatoes and many of them have really weird features like moniliform tubers, but many of them seem to have low glycoalkaloids and good disease resistance, most of which has been untapped.  The problems are those common to all wild potatoes - small tubers and long stolons.  One species that I grew this year, S. acroscopicum, had reasonable tuber size, short stolons, low glycoalkaloids, and short day tuberization.  It could potentially serve as a nucleus for work in clade 3.

I think there is a lot of potential for doing interesting work from mixed gene pools of diploids within each clade.  It isn't likely that we will ever see a serious competitor to the domesticated potato from these species, but I think it should be possible to select perfectly acceptable edible varieties with potentially superior pest and disease resistance.

The attachments show a large S. acroscopicum tuber and a very impressive USDA selection of S. ehrenbergii.  Most tubers are much smaller and most plants have a much lower average size, but you can see the potential.
« Last Edit: 2018-11-03, 05:52:20 PM by bill »

S.Simonsen

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Re: Working with wild potatoes & breeding by clade
« Reply #1 on: 2020-08-19, 07:15:12 AM »
I am interested in clade 3 personally. Has any work been done on crossing wild species within this group and if so how likely is cross compatibility in interspecies crosses? Retracing the route to the domestic potato presumably would rely on the right fortuitous hybrid followed by increasing ploidy. Would storage of mixed pollen from as many clade 3 species as available then applying that to emasculated flowers of the most promising nucleus species with at least some promising agricultural traits be the way to approach it? If something interesting sets then working backwards to determine the pollen parent should be easier than trying to handle pollen from each species individually (though I guess there is a risk that one species that has more compatible pollen might swamp out more interesting ones that would only produce a smaller number of seeds, though on the other hand doesn't persistence of berries depend on having a minimum number of viable embryos? Maybe the more abundant pollen parent embryos could help stabilise a berry with only a few embryos from less viable parents).

bill

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Re: Working with wild potatoes & breeding by clade
« Reply #2 on: 2020-08-19, 03:51:35 PM »
Clade 3 mostly contains lesser known species that haven't been used much in potato breeding.  They are mostly diploid species, about 2/3 with 2EBN and 1/3 with 1EBN.  The difference in EBN will be a barrier to easy crossing, but I expect that the two EBN groups will mostly be compatible for crossing within group.  In general, species with the same ploidy, EBN, and nuclear genome can be expected to cross to some degree.  You can find a list of clade 3 species here and each profile notes in the Breeding section if there have been reported crosses with other species. https://www.cultivariable.com/instructions/potatoes/how-to-grow-wild-potatoes/?clade=3

Solanum chomatophilum seems to be the most studied species in clade 3 and has been crossed with many other species in clade and out.

I have had berries with a single seed.  For that matter, I have had entirely seedless berries fairly commonly from some crosses, so I don't know what effect the number of embryos has on berry development.

A good understanding of EBN is the most important tool when it comes to predicting the results of crosses with wild species:
https://www.cultivariable.com/potato-a-ploidy-primer/