Re: HYB: backcrosses, etc...

--- In iris-talk@y..., mahlberg s <s_j_mahlberg@y...> wrote:
> 
> Dorothy,
> I was aware that diploid, tetraploid, and triploids exist. What I 
need to know is where I can find out which iris are which at least 
with the ancestors? Where is this info available? thanks,
> steve mahlberg zone 4b duluth, mn

Steve,
Books like "The World of Iris" (hope that's correct) have some 
chromosome number information, especially of the species.

Just off the top of my head....

some 24 chromosome (diploid) species are: pallida, variegata, 
suaveolens var. mellita, imbricata, cengialtii, illyrica, and albertii
(??)

Some 48 chromosome (tetraploid) species are: aphylla, mesopotamica, 
trojana

I'm working on getting together a list of 24 chromosome varieties, 
many of them Miniature Tall Beardeds. I'll post about it when/if I 
get it together.

And on another note, "TWOI" I think, mentions that in crosses of 
diploid seed parent x tetraploid pollen parent that 40% of the 
resulting seeds grow up to be tetraploid, because irises have what's 
known as a "triploid block". This block prevents the formation of 
many of the possible triploid embryos, which gives you a better than 
expected ratio of tetraploids to triploids. Theoretically there would 
have been very few (relatively speaking) tetraploids from such a 
cross. On the down-side I don't think there are usually many (if any) 
seeds that form at all from this type of cross. You have to be really 
persistent.
Good luck,
Tom


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