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Re: HYB: 2nd year sprouts
iris-photos@yahoogroups.com
  • Subject: Re: HYB: 2nd year sprouts
  • From: Linda Mann <lmann@lock-net.com>
  • Date: Fri, 25 May 2012 10:41:28 -0400

 

> > Inbreeding depression. T During this process secondary traits such as
> germination, branching (cold hardiness) etc can loose some of its
> variability and get trapped into a restriction. This can only be broken
> by crossing into a line that does not have this problem, and selecting
> carefully on this trait.

Right, that's what I was saying (or trying to say).

> So, for example, inbred pink lines can end up with a trait which
> requires less vernalization for germination. But when lines are
> crossed, these traits will become less distinct.

But only if they are crossed with cultivars with a range of
characteristics - my impression is that pinks (for example) were inbred
for a long time. Added limitation of bloom season - most crosses are
made between cultivars that are blooming at the same time.

[My impression is that the earliest germinants - by early in this case,
I mean early in the season, i.e., cooler temperatures (?) - are also
early bloomers - no idea if this is true - anybody have data?]

> While some traits can be located close to others, and be linked, in
> this situation, this is a less likely scenario, although possible.
>
> The tangerine factor, for instance, has been noted , by you, as
> needing less vernalization for germination. Likely a variability
> selected out. So if linked, a group of seedlings having some
> tangerine factor and some not having ( as in example being addressed),
> the tangerine factor seeds would germinate faster ,and be more
> represented in first year germination, rather then in second year
> germination.

Some blurring here - there seem to be a lot of late blooming t factor
cultivars that are <not> pink. Part of what makes me suspect the early
germination/low chilling requirement for (some/most/sure not all?) pinks
is just a coincidence of origin. So might be the 'white' genes (removal
of anthocyanin) associated with tangerine in those early pinks. So
early <pinks> is not opposite of report from Mary Lou.

<The opposite of what was reported.>

I understand that.
> Then we have to look at math. Probabilities and distribution curves.
> That is all offspring of a cross will be on a distribution curve. With
> a mean and a standard deviation, for all traits involving multiple
> genes. For example petal width, petal size, petal strength. So when
> one group of seedlings has one set of means and SD, different then a
> separate set, then probability of being samples from same population
> set becomes extremely low.

Right, I'm suggesting it's not random.

> So you are not going to get a set of poor seedlings for one year
> (one sample set) and a set of good seedlings in second year (second
> sample set), by random.

I'm not sure I follow this - seems to contradict what you were saying
earlier about inbreeding and suppression of variability.

Staying with pinks for the moment, very very few pinks have much, if any
resistance to foliar 'summer crud' - bacterial/fungal leaf spot. (I
haven't tried to separate out the two here - local extension folks say
it's bacterial, all irisarians say its fungal, I just call it crud). So
color and susceptibility to crud may not be 'linked' (i.e., on the same
chromosome), but they do co-occur.

Assuming you are correct in saying they are not genetically linked, can
you come up with some other explanation for skewed distribution of
co-occurring vegetative (health, temperature regulation) and
color/pattern traits? Or are you saying that it just doesn't exist.

If we are looking at possible genetic linkage,
> then there would have to be linkage of tangerine factor, and multiple
> genes associated with substance and petal size linked with each other
> and with germination factors, such as vernalization genes. Sorry, a
> very improbable situation.

Also, I'm curious how amphidiploid nature of TBs feeds into probability
distribution for traits.



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