Not sure what would be the difference, but can venture a couple of guesses.
1)WithTB X AB, it could be lack of gene compatibility.
2) The crosses I make of vigorous plants with fast increase with plants that rebloom here, may vey well be getting vigorous genes from both sidess. Any plant that has good rebloom herer in Southern Ontario, has to have high vigour and fast increases t ostart with. Otherwise it falls victom to environment
3) Low mature leaf count plants bloom earlier both in spring and in fall rebloom.
The studies of 2nd generation crosses of brevicalis and fulva showed bloom timing to be a very complicated muly genetic trait. A large number of genes involved.
But whatever is happening, it does work for me. I've outlined a number of crossesnext year to explore this further.
From: d7432da <email@example.com>
Sent: Sun, Jan 9, 2011 12:26 pm
Subject: [iris-photos] Re: HYB seeds from "Cloud Shadow"
> I would suggest plant vigour
My experience with ABs and TBs is that plant vigor has low heritability. I don't work with rebloom, but the results using plants with lots of vigor and hardly any as either both or one parent haven't had much predictability showing up in the seedlings. I think increased vigor may be a cumulative thing, but it doesn't seem to take much loss of something in the mix to send it down the slide. For this to be working, you must be having better success than I've seen. What's the key?
Texas Zone 7b, USA