HYB: Wide Crosses
- To: i*@onelist.com
- Subject: HYB: Wide Crosses
- From: S* M* <7*@compuserve.com>
- Date: Sun, 26 Jul 1998 14:55:01 -0400
From: Sharon McAllister <73372.1745@compuserve.com>
Shanna DeSotle wrote:
> I think that the 'wider' the cross, the more problems that will arise.
(The
> more dissimilar the parents, the worse the child.)
And Gerry Snyder replied:
> This is certainly true in some areas, but in others there is the concept
of
> "hybrid vigor" when the parents are "unrelated" but "compatible."
> Maybe the seeming inconsistency just means that "wide" may be okay, but
> "dissimilar" is riskier.
> Comments?
1. "Wide" is relative.
2. Risk and reward go hand-in-hand.
Yes, the wider the cross --
the lower the percentage of takes
the lower the germination rate
the higher the infant mortality rate.
But ALSO, the wider the cross, the greater the chance that one of the few
which do survive will be exceptionally vigorous and prove to be a
significant breakthrough.
When I started hybridizing over 20 years ago, I polled a number of
established hybridizers [those who had been working for 25 to 50 years with
both arilbreds & TBs] for a NL article. The consensus was that about 1 in
50 to 100 arilbred seedlings prove worthy of introduction, compared to less
than 1 in 1,000 TB seedlings. Overall, I've found that rule to be on the
mark -- but halfbred lines meet those criteria year-by-year while the wide
crosses are extremely variable.
Take, for example, the five-year period from the '77 bloom season through
the '81 bloom season. I bloomed hundreds of tetraploid 3/4-breds from
crosses made during those seasons, before finding even one I considered
worthy of introduction. For the entire period, the selections didn't reach
that magic 1 in 100 mark -- the stats for '77 through '80 say "why bother",
but those for '81 yell "JACKPOT!"
I believe it is this extreme variation in results which leads some people
to dismiss wide crosses and others to be drawn to them, becuase it's very
important not to judge the results of wide crosses on the basis of a small
sample. Wide crosses have their own special purpose in hybridizing
programs, as do line breeding and outcrossing -- but they're also great fun
for people with more time than space for seedlings.
Sharon McAllister
73372.1745@compuserve.com
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