Open Source F1 Hybrids

[gmuller]

I've been wondering about what to do with some purple CMS carrots I'm growing next to my short fat coloured carrot project. When the non-CMS is stable (sooon, please...), it would be possible to grow it next to the purple CMS carrots, then start selecting for short fat coloured CMS carrots. Keep the lines separate, but grow in parallel. Could then offer a double packet of short fat coloured carrots with a CMS line and a fertile line, so growers could create their own F1s.
How many people would be interested in investing the time in growouts and seed production is debatable.
G

[Klaus Brugger]

Do I understand you correctly:
You do not work with a restorer gene and the short fat fertile line would basically be your maintainer and after some years you have a line with the nuclear genome of your fat fertiles but the "sterile" cytoplasm of your once purple cultivar? And people could maintain this fat CMS line with your fat fertile line (both in one packet) and use the CMS line for crosses with male parents of their choice?
That's actually a very nice thought!

[Andrew Barney]

I don't know if CMS works like mitochondria does in humans,  but although somewhat rare,  occasionally (and sometimes it runs in families) paternal mitochondria can be passed to the young and mitochondria DNA swapping can occur. Some people even have two sets of mitochondria DNA lines (one originally obtained from a father gamete).

I sometimes wonder how often CMS lines spontaneously fix themselves and become fertile again.

[Walt]

It is possible that mitochodria sometimes are carried through the pollen.  I haven't read of it, but chloroplasts, which are generally thought to be received from the seed , sometimes, in some species, are transmitted via pollen.
But the hybrid seed industry is based on the stability of cms;  And it seldom, if ever, lets them down.

[Klaus Brugger]

I just read an old (!) but interesting review¹ about carrot breeding again. It talks about different CMS systems in carrots and also a bit about spontaneous restoration of pollen fertility.
In any case, I think you've got good chances to get viable pollen from a CMS hybrid when you're growing it under the "right" conditions and I wouldn't wait/hope for biparental inheritance of mitochondria.
Reading the review also reminded me that with the resources I have, breeding a good hybrid carrot is probably impossible. Well, I prefer growing squashes anyway . 
 

¹Stein, M. and Nothnagel, T. (1995): Some remarks on carrot breeding (Daucus carota sativus Hoffm.). Plant Breeding, Volume 114, Issue 1, p. 1–11. https://doi.org/10.1111/j.1439-0523.1995.tb00750.x

[gmuller]

Some thinking while I write...
I haven't done any research at all on this, just musing.
My Thoughts were to grow the purple CMS carrots next to my fertile short fat purple (SFP) carrots that I'm trying to stabilise.
Any seed from the purple CMS carrots will have been pollinated by the fertile SFP carrots, and hopefully inherit the SFP characteristics, while still retaining the CMS.

Next generation, grow the offspring from the two lines in parallel again, searching for SFP carrots in both lines.

I've just realised the flaw in this - the lines will eventually share much of the genetic material. So the chances of getting hybrid vigour will be reduced with each generation. At least in the nuclear genetics... I could split my SFP fertile carrot lines now, grow one line in isolation while doing the parallel growouts at some  physical distance, and hope for genetic distance between the populations as well. Hmmm.

By chance, the CMS purples are growing next to a totally unrelated grex of short fat orange carrots - this would give a distinct genetic pool to draw from - but would also add a number of years to my project as I tried ro start selecting for SFP again...if I kept the lines distinct from my already stabilising line, I might get hybrid vigor out of a future cross between the new CMS SFP carrot , and already existing one.

So, then offer two distinct packets shipped together, one CMS SFP, along with my original ertile SFP carrot, so growers could make and maintain their own F1  SFP carrots - that would be CMS.
...There might even by more than one person in the world interested in doing it
G

[Klaus Brugger]

I think there are two major obstacles:

• You need a good maintainer. One that doesn't (partially) restore fertility in your CMS line. At that would have to be a third line shipped together with the two hybrid parents.
• You need to find a combination between highly inbred lines that, in the F1, is not worse than a good OP variety and I'm not sure how easy that is. You probably want highly inbred lines for your CMS to be stable and inbreeding depression is likely to be an issue.

I'm not sure how purple color is inherited in carrots, but maybe you still get SFPs when only one parent is SFP and the other is SFO?
I think it's quite difficult to select for a new CMS SFP in a cross between CMS purple and fertile SFO. You first need an unstable sterility to be able to do such selection but in the end you again want the sterility to be stable.

These are just some thoughts and in no way do I want to discourage you  . I think this a very interesting project, but a quite difficult one.

[gmuller]

Klaus,
I'm concentrating on my Short Fat Purple fertiles at the moment - they are hard enough to stabilise. The rest is musings and thought experiments - which I might investigate if and when the first stage is complete.
Thanks for your ideas tho - it seems a bit more daunting than i thought.GM