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Re: MDBs continued.

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: Re: MDBs continued.
  • From: birddog@mnsinc.com (Ryan S. Carter)
  • Date: Tue, 2 Sep 1997 18:01:22 -0600 (MDT)

>Ryan wrote
>>        As a follow-up to my question about reblooming MDBs, (this may seem
>>like a stupid question to ask but...) what other developments are there to
>>be made in that field (i.e. color, form, hardiness, diploid-to-tetraploid,
>This is a great question, one close to my own heart. First of all, this is
>wide open field. There are not many hybridizers of MDBs, and most of them
>don't have planned breeding programs, but just take advantage of
>opportunities as they appear.
>Virtually all the MDBs are tetraploids, but several different kinds of
>tetraploids are present. Understanding this is the key to planning a
>successful breeding program.
>First, there are MDBs that are pure Iris pumila. This diminutive species is
>in the background of most MDBs, SDBs, and IBs today. It is unbranched,
>typically 3 to 4 inches tall, and very early blooming. There aren't too
>many pure pumilas available on the market now. With effort, I've been able
>to build a collection of less than a dozen. These are 32-chromosomes
>tetraploids. I use the notation PPPP to represent their four sets of pumila
>chromosomes. These are generally fertile, especially amongst themselves,
>although I find the vagaries of early spring weather often foil my attempts
>to hybridize on them, and they are so small that their tiny pods don't hold
>the massive quantities of seed you may be used to with TBs. Pumilas require
>lots of winter cold to survive and bloom well. Examples: Baby Tiger, Daring
>Eyes, Buzz Bee.
>Next, there are the MDBs that have the same chromosome breakdown as the
>SDBs: two sets of pumila chromosomes and two sets of tall bearded
>chromosomes, PPTT, for a total count of 40. Most of these are "unplanned"
>products of SDB breeding, which just happen to be small enough to fall in
>the MDB class. MDB pinks and plicatas are essentially all in this category.
>They are the most adaptable MDBs for warm climates and tend to bloom late
>in the MDB season. These are also quite fertile, and obviously breed easily
>with the SDBs. The problem, of course, is that since these are basically
>small SDBs, they tend to produce seedlings that are too large for the MDB
>class. Examples: Ditto, Fairy Lore, Knick-Knack.
>Finally, there are MDBs that come from SDB x pumila crosses. They end up
>with three sets of pumila chromosomes and one set of TB chromosomes: PPPT,
>or 36 chromosomes altogether. They are less fertile than the other two
>types, but in many ways they combine the best of both parent types: lots of
>different color patterns, reasonable performance in various climates, and
>reliably small size. They would be ideal for a breeding program, were it
>not for their limited fertility. Examples: Crocus, Zipper, Alpine Lake.
>[Knowing which MDBs are in which category usually requires some pedigree
>research. I have a fairly complete list of 32-chromosome pumilas, and I'm
>working on a list of 40-chromosome MDBs. They may end up on my web site
>some day.]
>I think the future of the class lies with the 40-chromosome group. Unlike
>the 36-chromosome group, they have enough fertility to make long-term
>breeding plans possible. Unlike I. pumila, they have the added advantage of
>color patterns from the TBs and growability in mild climates. The challenge
>is to develop a line that produces reliably small plants, rather than 75%
>or more SDB-sized seedlings. Ben Hager worked on this for many years, with
>significant (but slow) progress. Ben believes (and I agree) that the key to
>keeping the 40-chromosome group small is using I.aphylla-based medians,
>rather than TBs, in their breeding. In other words, instead of starting
>with typical SDBs (which are bred from TB x pumila crosses), use tet MTB x
>pumila crosses to start the line. Even doing this (Libation is an example),
>Hager found most seedlings are too large for the MDB class.
>I think there is now more potential than ever in this line, because the tet
>MTBs that have been derived from I. aphylla are improving in quality and
>becoming daintier. (The Craigs have already introduced two 48-chromosome
>SDBs from these lines.) Using the newest, smallest tetraploid medians with
>I. pumila should improve the chances of establishing a line of reliably
>small 40-chromosome MDBs. I've made crosses to this end, but am still
>waiting to see if they lead to anything good.
>So here's the short version:
>What needs to be done? Develop MDBs with
>- more different color patterns
>- more modern form (eliminate tucking and increase width)
>- better adaptability to both mild and cold climates
>- consistent small size and daintiness
>- reliable fertility for line breeding
>How to do it?
>- start with the current 40-chromosome MDBs (mostly from Ben Hager, but
>there are others too)
>- get some I. pumila MDBs and cross them with the smallest, newest
>48-chromosome medians, such as the tet MTBs
>- line breed the Hager MDBs (and possibly some of the daintiest SDBs) with
>the pumila/median hybrids, always selecting for small size and modern form
>Persisting in the plan for three or four generations should produce a good,
>working line of 40-chromosome MDBs, distinct from Hager's but crossable
>with it. Such outcrosses can then be made judiciously to enhance vigor and
>bring in new desirable characteristics.
>Tom Tadfor Little                       telp@Rt66.com
>Iris-L list owner  *  USDA zone 5/6  *  AIS region 23
>Santa Fe, New Mexico (USA)
>Telperion Productions      http://www.rt66.com/~telp/
>Iris-L Web Site  http://www.rt66.com/~telp/garden.htm

Thank you so much Tom. I will do this and also get more advice on it from
Dr. Spoon.
This is so good that I will print it out.


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