My contribution to the seedlings-and-rust conversation... and fwiw I live in zone 9b.
I had a couple of flats of seedlings (jammed several per 4" pot) sitting in my side yard last winter (2014-2015). When I went to start potting them up in January, I found that pretty much all of them had been infected with rust.
(Last winter I ended up purging quite a few potted named cultivars from that area, due to heavy rust. I had bought several new plants that year, so I don't have much doubt as to where the rust came from.)
I pitched some of the seedlings that were the most heavily affected (those were from crosses with rust-susceptible near-white tets), but pulled a few leaves and kept most of them and eventually planted them out. (I decided to build a new seedling bed instead of potting them up, and for one reason or another it took until November to get them all planted out.
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We have had quite a bit of rain here the past few months, and while some established cultivars here currently show some rust (there are a few rust buckets I am keeping for various reasons), the seedling bed thus far looks pretty clean. The only sketchy looking seedlings (no pustule eruption, yet, just suspicious looking yellow areas on the foliage) are those from the near-white tet crosses, and that is to be expected. (My pollen dabbing in that vein is to get some near-white tets that do have resistance.)
Since many of the other seedlings come from 'Hip To Be Square' (I read somewhere or another that it was considered rust resistant and for the most part it is here, though it too got some rust that awful winter (it lives in that same side yard that had the horrifyingly ultra heavy rust density that year)), I have some hopes that the mature, blooming size plants will also show some resistance. (I also have hopes that said plants will also be polymerous, but that's another matter. I am hoping it is not to much to ask for polymerous + rust resistant in the same plant(s)...
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