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
