HYB: Reciprocal Crosses
From: Sharon McAllister <firstname.lastname@example.org>
> I will dive right in at the end. :-) When you make reciprocal crosses,
> mix the seed or do you plant the seeds separately? If you plant them
> separately, do you see a differences in the two crosses?
ALWAYS keep them separate. That's the point of the test. After analyzing
some 20 years worth of such seedlings, I've concluded that reciprocal
crosses can be divided into two types: those with similar and those with
different types of cytoplasm. There's a logical reason for this, as the
cytoplasm is what carries the extra-chromosomal DNA. I suspect, however,
that it's not all that simple. Sometimes it seems that there are enabler
genes carried by the cytoplasm that affect the expression of chromosomal
Never say "never" -- but so far no reciprocal cross involving parents that
have the same type of cytoplasm has produced a set of seedlings that can be
discriminated at a statistically significant level.
Reciprocal crosses involving parents of different maternal lines are a very
different story. For example, I crossed JUST FOR JAN [korolkowii maternal
line] and KIOSK [onco maternal line]. Both are yellow, with burgundy
signals. JUST FOR JAN is a slight bitone, while KIOSK is a near-self.
JUST FOR JAN's signal is elongated, while KIOSK's is more rounded. JUST
FOR JAN's form is rather tailored, while that of KIOSK is almost billowy.
I raised over a hundred seedlings of these two crosses to bloom size. All
were a combination of the parents' color, pattern, and form --and all
combinations turned up in both groups of seedlings.
Plant characteristics were another matter. JUST FOR JAN has open,
spreading growth habits, and it's mature daughter rhizomes separate
naturally from the mother rhizome. KIOSK has very tight growth habits.
Left in place too long, JUST FOR JAN will take over some of its neighbors
territory while KIOSK just commits suicide. It looked as though the plant
type of the seedlings favored the growth type of their pod parent, but I
didn't want to leave them in place long enough to see which were truly
invasive and which were suicidal so when I dug those beds I carefully
compared the rhizomes. The differences were so noticeable that I do
believe that if someone had mixed up the lot while my back was turned and I
could have quickly separated them again.
> Not content to let it rest at that, I wrote to some well-known
> outside our region. Reciprocal crosses was only one of many questions I
> asked. (For those who helped--Thanks again.) I was surprised when I
> that there were no differences in the two groups of seed. One
> hybridizers, who I have utmost respect for, replied that he just mixed
> seeds together and planted them as one cross. He said there was no
I'd bet this was a TB hybridizer. I don't know of anyone who has done
experiments with reciprocal crosses of TBs who had sufficient information
about the cytoplasmic type to perform an actual discriminant analysis.
This does, however, conform to my own observations with reciprocal crosses
between cultivars having similar cytoplasm.
Guess that would be a good HYB 301 homework assignment -- determine whether
any of your TB breeding stock has a maternal line that is traceable back to
species. [Assuming, of course, that no stray bit of pollen contaminated
any cross down through the generations.]
> For those who wondered out loud why I would make such a dumb cross as
> Spot and Highland Chief, you now have your answer! Peach Spot is a West
> rebloomer and Highland Chief is still a favorite brown/red plicata. I
> made the reciprocal cross. I eagerly lined out my seedlings, and
> awaited their bloom in 88. My first babies to bloom--what a thrill!
> blooms from this cross were a delight to see. And very different. Each
> the other and between crosses.
> Where I had used Highland Chief as the pod parent, I got plicatas with
> orange selfs (9 buds) thrown in. There were several very pretty irises
> this group. Where I used Peach Spot as the pod parent, I got pale
> amoenas and some off-colored whites. On these, 5 was the highest bud
Sounds like a good homework assignment, to me. <G>
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