The Tropical Fruit Forum

Akebia is right.  Working for zone 6 hardiness will have spinoffs for zone 7.

As always I'm impressed with your work/

I did grad work in genetics but I was studying vegetables and grain so this might not appply to citrus.  If anyone does know the effects of tetraploidy in citrus, listen to them, not me.
In vegetables, a few species have more vitamin  C in the tetraploid than the diploid.  But generally the difference is small or none at all.
In grains, wheat, rye and barley, tetraploids tend to be slightly less cold hardy than the same variety at the diploid level.  That is for rye (Secale cereali), barley (Horeun sativa) which are normally diploid.  Wheat (Triticum species) has diploid, tetraploid, and hexaploid species.  In Triticum, we can't directly compare diploid vs higher ploidy because there has been centuries of selection for different climates so the genetics is much more important than ploidy.

So I expect the difference between diploid and tetraploid citranges to be small.  But there are a few plant families that don't follow the general rules.  So it is possible citrus don't follow these general rules.

I've never heard of it being illegal in the USA. Is there anyone here who keeps up on these things?  It's been 40 years since I was up to date on this.

Adding wild flower is a good idea.  But the town has been spraying for mosquitos for so many years that bringing in pollinaters is also a good idea,  Preferably native species that might become re established in the area.  An idea I just had istoget a hive and keep it most of the year on a nearby ranch.  Bring it to the orchard (breeding area) during bloom and moving it back for the rest of the year,  But I'd have to check what is being sprayed on the ranch land,  Aerial spraying is a big industry here,

ery encouraging results.

Its good to have another person working on more winter hardy citrus.  Being in zone 7 I think you will get a bigger percent of survivers than Kumin in zone 6.  If vnomonee's fruit's seedlings do have trifoliate leaves, then that will jumpstart your work.   There was a thread active a while back on crosses of Ponciris and kumquat.  The discussion went that many kumquat x Ponciris hybrid seedlings lacked vigor and died young.  But some were vigorous and grew well.  So don't get discouraged if your success rate is low at first.

I have also heard of having compost piles in greenhouses for the added CO2.

Or if you are willing to grow in a pot and bring iy inside winters, you have some options.

or if you are willing to wait an unknown number of years, there will be some other options for outside, in ground.  We are working on it.  But not today.

And all of this is due to fusion power in the sun.  With a lot of help from the greenhouse effect. 
When I was growing up, temperatures of 100F made the news reports now and then.  People would talk about it for days.  But this summer we had 100+ (40-45C) day after day, week after week.  I got really tired of it.  And the garden suffered from it.  Other places had it much worse, of course.

I believe Meyer lemon is zygotic, so the fruit will not be exactly like a Meyer.  If the fruit isn't good, you have a nice tree to graft other varieties onto.

Actually, when I started working on cold hardy citrus, I thought they were 30 years away.  Now I'm thinking as little as 5 years away.  Maybe.
Fusion power?  Maybe in my life time.  But I plan to live a long time.