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
