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Topics - bill

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Potatoes / Viruses in Certified Seed Potatoes
« on: 2020-02-17, 01:15:09 PM »
Certified seed potatoes are the most disease free option available to potato growers (other than TPS), but they are not disease free.  There are tolerances for various diseases.  For some, the tolerance is zero (most bacterial diseases), but for viruses, there is generally an allowance.  So, you can get any of the common potato viruses from certified seed.  The most common virus that I see in certified seed is Potato Virus S (PVS).  Most programs don't have an upper limit for PVS infection.  PVS is generally considered to be a virus of minor importance, but is has a number of undesirable effects, particularly if you are saving your own tubers year on year.  PVS, in my experience, makes potatoes much less likely to hold flowers.  It also amplifies the symptoms of other viruses and can reduce resistance to late blight.

The picture shows test results for the variety 'German Butterball,' received from a major certified seed supplier this year.  As far as I could tell, the whole lot was infected with PVS.


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Tinkering / How to organize the plant breeding forums
« on: 2020-02-07, 03:14:17 PM »
We have added a number of subforums, but there is not a particular method of organization currently.  For example, we have a greens subforum, which obviously accommodates many species that might be taxonomically distant from one another, and then we have specific crop subforums.  It already appears that there would be benefit in having a higher level forum than tomato or potato, since we have a number of posts that discuss both.  I guess the question is whether or not the top level plant breeding forum is a good enough place for those, or if they need their own place.  Having a greens forum would make good sense at plant growing forum, but for a plant breeding forum, where taxonomic relationships matter much more, it seems insufficient.

Homegrown Goodness attempted to organize with top level forums at about the family level.  That might be a good idea.  Should we adopt a more consistent organization and, if so, what should it be?  If we do, how deep should the nesting go?  For example, is a Solanaceae forum good enough or should we have a Solanaceae forum with Capsicum and Solanum subforums and then a Solanum subforum with eggplant, potato, and tomato forums?  Or should we have a Solanaceae forum and then just go straight to crops, so subforums for eggplants, Physalis, potato, tobacco, tomato, etc.


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Potatoes / Virus Cleanup of the Variety Purple Star
« on: 2020-02-06, 02:21:13 PM »
Purple Star is a variety bred by forum member nathanp.  I just started the process of cleaning it up and I will do a video for each stage of the process:

https://www.cultivariable.com/purple-star-potato-virus-cleanup-part-1-initial-testing/

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Potatoes / Fine Tuning Germination of Older True Potato Seeds
« on: 2020-02-06, 02:15:39 PM »
I did a little experiment this year to see if I could maximize the germination of older TPS.  Best results were obtained with surface sown seeds, covered by plastic, under direct light.

https://www.cultivariable.com/fine-tuning-germination-of-older-true-potato-seeds/

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Would you be interested in doing some participatory plant breeding this year with Andean or wild potatoes, oca, or dahlia?  If so, please take a look at the link:
https://www.cultivariable.com/cultivariable-participatory-plant-breeding-projects-2020/

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Tinkering / OSSI Varieties forum?
« on: 2018-11-11, 05:29:09 PM »
Should we have a forum for OSSI varieties, where people can post their creations and discuss them?  The alternative is just to discuss them in the plant breeding forum, but a separate forum might encourage people to participate.

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Potatoes / 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.

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