Re: Stability of tetraploid Siberians

Hi Jeff, and Robins,
 I have lots of experience with Tet germplasm in daylilies and a few other
perennials.
 I believe that the following holds true, as a general rule, for all
perennials.
 Any plant that has been induced to be tet with colchicine, orazylin, or
naturally occurring has a large chance of having both dip and tet pollen. The
exception would be full conversions, which are not too common, but very
possible. Full conversions are those that all cells in the plant have been
converted to tet. Many times these will be both pod and pollen fertile.
 More than 90% of all conversions have both dip and tet pollen, plus, broken
pollen, and will be very difficult to set pods on.
  The big, good news, is that if you place tet pollen from a conversion on a
tet derived by sexual means, and cap the cross to prevent insect crosses,
that the progeny will be full tet in almost 100% of the cases. Where one sets
pollen on converted tets, the outcome is iffy and must be ascertained by
microscopy.
 Almost all tet pollen is 40% bigger than dip pollen- in my experience. If
you look thru a microscope with a measuring reticle at converted pollen, you
will usually see a range of sizes. This means that the conversion is not a
full conversion. These conversions will sometimes revert to dip and sometimes
remain stable. There is usually lots of broken pollen in a conversion too.
This pollen is non viable.
 As a general rule of thumb, always use the converted parent as a pollen
parent to ensure tet progeny. If you use the converted parent as a pod
parent, you can not be sure that the conversion and subsequent progeny will
be fully tet, and they might be dip. You would not find this out for two
years, in those without laboratory resources.
 As to different numbers of chromosome counts, it is very tough to make
crosses if the counts do not match up. The father of modern daylilies, Arlo B
Stout, made tens of thousands of crosses between Hemerocallis Fulva, a
triploid, and other diploid species to generate a handful of viable seed.
Crossing triploids is very difficult, even if the numbers match.
 Perhaps Marty and Jan, or someone with lots of Iris experience could comment
further and correct me! Jim

dunlopjj wrote:

> Greetings to all.  Recently I've been thinking about the stability
> of tetraploid germplasm in Siberians.  My considered opinion is that
> even converted material (P1) used with stable tets, should produce
> stable tet pollen and pods in the P2 generation and beyond.  Assuming
> of course, the P1 cross took as tetraploid without reversion
> (reversion giving no seeds or nonviable seeds), or without altering
> the P1 cross progeny to another state of ploidy (to triploid,
> octoploid, etc).  Can we count on tetraploids in the P2, P3 and
> higher being very stable?  Also does anyone have a grip on
> statistical probabilities of reversion or alteration in ploidy level
> in the P2 or beyond?  Thanks for your help.
>
> Jeff Dunlop
>
> To post to Sibrob: sibrob@yahoogroups.com
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/



To post to Sibrob: sibrob@yahoogroups.com 

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index