GardenBanter.co.uk - View Single Post

11-02-2003, 08:55 PM

ostheap (VoySager) wrote in message ...
jcart003 wrote:

In reality there is no way that a cutting from your
diseased plant would be genetically altered. The DNA damage you
mention is on a single cell level and is random. Most mutations are
fatal, and therefore the damaged cell would die. If it didn't die it
would still be only one cell out of a billion or so. The reason for
not using diseased material is to avoid spreading disease, mostly
viral.

So, if I understand you correctly, the statement:

"There is a possibility that the disease has affected the genetic make up of
your plant which could mean that the plant (and clones made from it) will grow
slowly forever more. You might want to consider throwing your diseased plant
away and start again with healthy cuttings."

...is essentially untrue? And that, in the case of viral disease, a clone from
an infected plant would be affected by the virus, but not by any genetic
mutation that might have been caused in the parent plant by the virus?

Now if you were to do (agghhhhh an over 40 moment! I can't recall
the term!) the type of cloning (using the meristem, and seperateing it
to single cells) that they do in labs now you could create a
genetically altered plant from the scenario you laid out... reactive
ox. sp. causing DNA damage..... it would be shot inthe dark.... but
that is one way to get a new/unusual clone ie in orchids.

Tissue culture? So, in fact, from what you're saying, it takes a purposeful
attempt to cause mutation in the parent cells that would get passed on to the
clones, and even then it's an iffy proposition?

I see from your address that you're an educator or researcher? so I could quote
your response as a professional opinion from a knowledgable individual? (I
don't want to pry and ask you to identify yourself...)

Better yet, do you have any suggestions as to sources of info (links) on this
subject, preferably not too technical? I did a little bit of reading on the
subject of adaptive mutation today that would seem to question whether, in
fact, "the concept of genetic response to environmental stress died with
Lamarck", as Iris said earlier; but I couldn't even begin to try to argue that,
as I'm a dirt gardener, not a scientist.

I will stop here as I feel myself on a ramble through
bio/genetics..... there are lots of interesting permutations of
this...if you are a nerd.

Or, for that matter, ramble on if you wish, I at least will read your response;
I'm no nerd, I'd have to know more about the subject to even aspire to that
status ;-) , but as I said before, I was surprised at the statement above
regarding "disease-mutation-affecting-growth", doubted its veracity, and would
like to learn enough about the subject to be able to refute it.

Thanks for all the responses (except for yours, bayhill ["The reason the
economy became so robust had nothing to do with Clinton." etc.]... you're lost
in the wrong thread).

Bill
You seem to understand the topic quite well.
I am not a reasearcher! I have many hats! At the present time I am a
medical student.... but was formerly a farmer/nursery owner.... and my
undergrad was biochemistry, which has a good bit of genetics in it.
Now that pretty much says who I am, not many in this country with that
background!!..... no anonimity for me!
The statement about starting with new material is true, but not
for genetic reasons. The virus will be in the cuttings taken from an
infected plant, therefore affecting all future cuttings. In tissue
culture (thanks!) you can get the youngest cells and sometimes these
aren't infected yet, so it is technically possible to salvage a plant.
I think this was used in the early 1900's to salvage potatoes in
europe after devastating viral infections.
Now as to lamarck, well his theories wreaked havoc in the soviet
union, the state accepted his ideas (they fit into a Marxist frame, as
opposed to modern genetics with random "luck") and their agriculture
program was set up with these ideas in mind... eventually you could
breed a freeze tolerant tomato.... well that doesn't quite work.... in
the way that they thought. The genetic changes are by chance mutation
(there are a lot of mutagens out there, ie sunlight) not due to
enviromental signals/stresses. BUT you could argue that the mutagens
are enviromental stresses, and they can be, BUT lamarck thought that
the genetics would be altered by the stress to compensate for the
stress. IN FACT the changes are random, and only by chance (and a slim
one at that) would the mutation be beneficial.
The mutation doesn't need to be purposeful, there are ALWAYS
mutations in every organism. By increaseing the mutation rate you
increase the possiblity that you will get a new shape/color/pattern.
It is estimated that EVERY human cell gets over 1000 DNA
hits/mutations EVERY DAY (rats get 10,000!!!)!!!!! It is a good thing
that we have mechanisms to fix our DNA! People induce mutations in
plants to try and get a new trait, but it is a LONG shot! with our new
understading of genetics it will be/is possible to switch traits such
as color, shape between plants! Exciting and scary at the same time.
One last thing on the "genetic response to enviromental stimuli" and
lamarck, organisms can express different genes in different settings,
so there is a genetic response to the enviroment, but not at the germ
line level. Hmmmmm that is a key concept, GERMLINE vs SOMATIC(this may
truly only be an animal term but the concept is the same). For a trait
to be passed on it must be in the germ line, that is sex cells. While
you can clone plants easily, the original mutation had to occur in the
germ line, for the reasons I tried to get across in my first response,
a mutation in the somatic cells is only in a single cell and the
trait/cell would not be able to multiply enough to take over the whole
(unless you go to a single cell tissue culture scenario)...... ahhhhhh
how I do go on. I hope it makes some sense, I type very slowly and
hate to fix my mistakes... so if anything is to unclear I will try and
make it clear later!
I don't know of any links that would be useful, but you might try
"carolina biological supply" they sell kits for experiments in this
type of thing and I have found that companies often have good clear
write ups about the theory that their kits are based on! You can quote
me as a knowledgable source, I do know this stuff!

IT is very
interesting, even for me when I was a dirt farmer!