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Re: hosta-open DIGEST V1 #483


Jim:

>Jim Anderson had asked a question (number 1) regarding 
>similarities/differences between variegation in daylilies and
>hostas. I had declined to participate in this question because of my
>limited familiarity in daylilies.

There are very few variegated daylilies and they are mostly unstable. 
A variegated seedling will show up from time to time, but they tend to 
be mericlinal chimeras and few form a stable periclinal chimera.

>I summarized the concepts defined by Jones(1934) wherein chimeras 
>(multicolored adjacent tissues) are a result of mutations within 
>specific cells which create two or more colors within cells and 
>subsequent, corresponding tissues.

I think hosta people need to get away from thinking in terms of 
mutations as the cause of variegation in hostas and start looking at 
the problem from a logical point of view.  First, I don't know of any 
other plant genera like hosta.  Hostas are NOT mutating at any higher 
rate then any other plants.  When you look at any other plant genera 
you don't see the level of variegation that you see in hosta.  If 
hosta variegation was due to mutations then you would see the same 
level of mutations in other plants.  I know the Great Ben proposes 
mutations as one cause of hosta variegation and sporting, but Ben 
doesn't know much about botany.

Secondly, if you propagate enough hostas you see that certain types 
keep reappearing.  

Variegation in hostas is most likely due to either transposable 
elements or some other mechanism that turns genes on and off.

Some time ago I gave Ben a clue to figuring this out, but apparently 
he doesn't know enough about higher plants and apparently doesn't have 
the observational skills to figure this out, besides not knowing how 
to propagate hostas.  If you look at Francee in the spring you see 
that the margins are lighly yellow when the new leaf is still small.  
If you look at Patriot you see that the edges of new leaves are 
yellow, but a deeper yellow.  The leaves of Patriot have a wider edge, 
the color of the center is a darker green and if you feel the leaves 
they have a thicker, heavier feel to them.  If you propagate enough 
Francee you see this Patriot form showing up from time to time, but 
sometimes not as intense as Patriot.  Also, you get light green forms 
from time to time.  This is a POSITION effect.  I'm amazed that the 
Great Ben couldn't figure this out, especially considering he is 
suppose to be knowledgeable about fruit flies where position effects 
were first studied.  

This spring I had five sports out of Whirlwind from 7 plants.  Three 
of the sports had leaves that were folded in half with a narrow white 
center.  After the 4-5th leaf the new leaves started getting flater, 
but still with a thin center.  Now the newest leaves are pretty much 
like Whirlwind.  All three plants that had this initial type of leaf 
did this gradual change.  This behavior is not due to mutations.

In cats calaco coloring is due to turning off of one of the X 
chromosomes.  Some cells have the paternal X on while other cells have 
the maternal X on.  When the X chromosomes get turned on/off 
determines the calaco pattern you see.  Streaked hostas are the calaco 
cats of the hosta genus, except it's not a X/y based sex chromosome.  

In a two layer histogenic structure the corpus (L2) doesn't have the 
organized apical initials like the L1 layer does.  Therefor, the cells 
in the L2 apex can be a mosaic pattern of genes that are turned on or 
off, or a position effect through a transposable element - this would 
result in a streaked hosta.  A streaked hosta would revert to a 
"stable" edged/center variegation pattern when the cells in the apex 
of the L2 layer all revert to having the transposable element at the 
same location.  A edged/center hosta can revert to a streaked form 
when some of the transposable elements shift position resulting in a 
mosaic pattern in the L2 apex.  

Getting a good understanding of transposable elements is difficult.  
Genetics textbooks in the 60's and 70's don't discuss them because 
they were not understood well at the time, and by the 80's and 90's 
genetics textbools were being written from a biochemical and molecular 
biology point of view and also mostly ignore transposable elements.  
For those who might want to do some searching of the literature, 
search for articles by Barbara McClintock.

Now, I wonder how long it will be before I see this showing up in the 
Hosta Journal as Ben's latest theory on variegation in hostas.  I 
certainly hope he will give me some credit!

Joe Halinar

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