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Re: Re: OGB? Seedling

  • Subject: Re: Re: OGB? Seedling
  • From: smciris@aol.com
  • Date: Sun, 4 May 2008 14:38:53 EDT

In a message dated 5/4/2008 7:48:06 AM Mountain Daylight Time, donald@eastland.net writes:

What criteria do you use to assign a classification? I have so many
registered OGBs that are stubborn about producing seeds that I wonder
about this type of cross that has the appearance of an OGB but might
not be that. Of the few I've bloomed with the OGB- type AB as one
parent, they have all tended to resemble an OGB type bloom rather
than a traditional quarterbred type. The fertility has been a bit
better, but not nearly as reliable as the balanced OGBs that do work
for me. It's a puzzle to me.

I agree that this type can't be classified on the basis of what the flower looks like.  Some with almost OGB-like blooms prove infertile.  There's no single, definitive test so I look for several quantifiable indicators. 
1.    How does the pollen appear when examined under a microscope?  This is a lot like trying to classify 256 shades of grey as either black or white, but it does provide some valuable clues.    Are the grains uniform in size and normal in appearance with little chaff, like that of a fully fertile halfbred?  Are the grains sparse or have a high proportion of chaff, like that of a conventional quarterbred?   If the sample doesn't appear to match either type, do subsequent samples reveal a pattern that may have been obscured by the effects of weather? 
2.    What is its summer dormancy pattern?  Does it stay green-dormant like most quarterbreds or go almost fully dormant like most halfbreds?  I realize this test wouldn't work in all climates, but in the hot southwest seedlings from a single cross that have been lined out together seem to sort themselves out.
3.    How fertile is it and what types of seedlings does it produce?  Again, there isn't a single test but a series of tests to reveal a pattern.  Here are a few examples: 
If, when crossed with an OGB known to be fully fertile, it produces full pods with a high germination rate and seedlings that all appear to be halfbreds -- that's evidence that it's a halfbred.  If there's a lot of variation in the offspring (in terms of pollen assessment and dormancy pattern) -- that's evidence it's a quarterbred. 
If, when crossed with a tetraploid aril, offspring all appear to be 3/4-breds -- that indicates it's a halfbred.  If many offspring appear to be 1/2-breds -- that's an indication it's a 1/4-bred. 
If, when crossed with TBs, offspring all appear to be 1/4-breds -- that indicates it's a halfbred.  If many of the offspring appear to be TBs -- that indicates it's probably a 1/4-bred.
"Someday" perhaps karyotype analysis will provide the answers.  At least, we can dream of it....
BTW, pollen analysis is also useful in assessing the registered OGBs that are reluctant parents.  Under the old quantum system, many fully fertile halfbreds were registered as OGB- ot OGB+ because the code was computed from the pedigree.  Pedigree analysis and test crosses were therefore needed to identify promising breeders.  Under the modified chromosome set system, the proverbial pendulum has swung in the opposite direction.  Now cultivars from wide crosses that look like halfbreds and grow like halfbreds may be coded OGB even though they don't breed like halfbreds. The old tools can still be used, though, to sort them out.
Sharon McAllister

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