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Pre-existing genes a more likely cause of herbicide resistance than new mutations


From ScienceDaily:

Summary: New evidence suggests that herbicide resistance in weeds is more likely to occur from pre-existing genetic variation than from new mutations.

After exposing more than 70 million grain amaranth seeds to a soil-based herbicide, researchers were not able to find a single herbicide-resistant mutant. Though preliminary, the findings suggest that the mutation rate in amaranth is very low, and that low-level herbicide application contributes little — if anything — to the onset of new mutations conferring resistance, researchers say…

Any major stress that does not kill a plant can contribute to genetic mutations in its seeds and pollen, said University of Illinois crop sciences professor Patrick Tranel, who led the new research. Even the ultraviolet light in sunlight can stress a plant and increase the likelihood of mutations in its offspring, he said. Such mutations increase genetic diversity, which can be useful to a species’ survival.

“Resistance to herbicides comes from genetic variation in a population,” Tranel said. “If an individual weed has the right mutation that allows it to survive a particular herbicide, that individual will survive and pass the trait to its progeny.”

The relative contribution of new mutations to the problem of herbicide resistance is poorly understood, Tranel said. He and his colleagues hoped to determine the baseline mutation rate for a plant of the genus Amaranthus, a group that includes waterhemp, Palmer amaranth and other problematic agricultural weeds. They also wanted to test whether herbicide applications that failed to kill the plant increased that baseline rate…

Very few of the test plants overcame the herbicide treatment. Rigorous testing revealed that those rare plants that did survive were the offspring of seeds of weedy amaranth species that already carried the resistance genes…

“Herbicide resistance is an evolutionary process, and evolutionary processes are mathematical,” Tranel said. “If you know more precisely how plants will behave under different environmental conditions, you can develop equations that will predict how fast resistance will evolve.” Paper. (paywall) – Federico A. Casale, Darci A. Giacomini, Patrick J. Tranel. Empirical investigation of mutation rate for herbicide resistance. Weed Science, 2019; 1 DOI: 10.1017/wsc.2019.19 More.

Note: “New evidence suggests that herbicide resistance in weeds is more likely to occur from pre-existing genetic variation than from new mutations” vs. “Herbicide resistance is an evolutionary process, and evolutionary processes are mathematical”

It sounds as though the necessary evolution occurred a long time ago and that a Darwinian process just isn’t happening. But they are not likely allowed to discuss it that way.

See also: How Maize Corn’s Wild Ancestor Teosinte Prevents Maize From Breeding With It

Hazel @ 2 Forbes article refers to horizontal gene transfer ..... so resistance has nothing to do with mutation producing a new gene (protein) Johnnyfarmer
I agree with the OP except that I doubt mutation is ever the cause of plant resistance to herbicides. If mutation is the cause then the cause must be due to the production of a new protein or the modification of an existing protein to produce additional function (binding sites). The only other possible cause of increased resistance is if mutational loss of protein function could cause increased resistance to herbicides in plants.... and I doubt that could happen ??? Neo Darwinists have yet to prove their assumption that mutation can produce novel proteins.... but that assumption is assumed in this experiment. Consider the genetic modification of crop plants to make them resistant to the mostly non selective herbicide Roundup whose active ingredient is Glyphosate. Roundup was first produced back in the early 1960's and was eventually licensed to be used as a non selective herbicide and since it was trans-locatable in the phloem it could be applied to the top of the plant and carried to the roots making it advantageous for difficult to kill perennial weeds. With the advent of gene splicing plant scientists wondered if genetic resistance to roundup could be artificially imparted into crop plants. Eventually some weed species were discovered to have some resistance to roundup and subsequent experiments identified several proteins responsible for the resistance. So the genes producing those proteins were spliced into Corn. The result was somewhat disappointing as the genetically modified corn showed some resistance to Roundup but also was accompanied by an unacceptable reduction in crop yield. So scientists continued to search for other proteins which provided resistance to Roundup and eventually isolated a bacterium commonly found in soil which produced a protein making it resistant to Roundup. A gene splice resulted in imparting perfect resistance to Roundup in Corn.... thus spray application to corn killed the weeds but not the corn. ... But now about thirty some years after genetically modifying corn we are seeing species of weeds becoming resistant to Roundup. The active ingredient in Roundup kills plant cells .... but plants having resistance (including genetically modified corn) produce proteins which metabolize the active ingredient Glyphosate rendering it harmless to the plant. So if weeds are becoming resistant to Roundup then is this resistance due to mutations producing new proteins which can metabolize the Glyphosate ?..... Or is the increasing resistance due to pre-existing genes ? Obviously weeds showing resistance to Roundup will tend to survive spray applications and those plants will be the ones to carry the resistant genes to subsequent generations. The assumption that mutation produces new proteins is yet to be proved ... but universally accepted by Darwinists !!!!!! Johnnyfarmer
“Then why wouldn’t we expect any resistance in the population to have already existed?” Actually this is my real issue with Darwinian evolution It is the fact that it is what you would expect, but if a new mutation happened, with the resistance, that to is what would have been expected as well If a population had the resistance in the first place it could be expected and explain by Darwinian evolution However if the population developed it through genetic mutation this would also be expected and predicted by Darwinian evolution Darwinian evolution actually predicts both outcomes And this is where I start to take issue with it it becomes a circular argument and not even wrong There is no outcome that Darwinian evolution cannot predict or explain This is why the advent of genetics didn’t phase the theory at all. The theory is that malleable and it’s capable of actually encompassing anything and explaining almost everything I don’t know much of what it can’t explain. A while back I started performing an exercise to see what I could explain using the principles of Darwinian evolution, and I found there was nothing I couldn’t explain even to the point where I could explain why there was more matter than antimatter in the universe. Even the most puzzling questions in all the universe such as this can be explained by simply finding the simplest advantage and therefore through the process of natural selection it would be the only matter that we continue to exist because it was selected naturally do do it stability versus antimatter (hypothetical Conjecture on my part) Now science is capable of helping filter a lot of this out but is long as a few dates can be connected to support the conjecture it is explained away the phenomenon at that point. You can even use it to explain the Flying Spaghetti Monster. I’m not trying to be insulting to anyone here but I am being serious you can definitely explain it in a stepwise fashion, and natural selection, with exact mutation events explaining each change, even though it does not exist Now I read through the paper a bit but what I gathered was they were looking for a possible mutational change in a population without the presence of the pre-existing gene that made you resistant to the herbicide they were trying to do is something that many evolutionary scientists have been attempting to do for many years which is establishing equation for mutational rate which from my understanding has failed or has not bore much fruit, the mutation rate is very unpredictable or it just doesn’t happen. A.k.a. it’s Cancerous or stagnant What they found instead was that the only generations that survived were the ones that were related to the weed that had the resistance in the first place Now even though this is definitely an example of micro evolution and natural selection acting on pre-existing genes, (Well technically natural selection doesn’t exist, it really doesn’t act on anything, and if you wanted a giggle listen to one of Richard Dawkins speeches and replace natural selection with God, he sounds like a Baptist minister) no new novel genes were created or generated, Which would be the ultimate smoking gun of Darwinian evolution showing that new information Can you tape it into existence from pre-existing genes creating all new traits and genes. So in the paper they were hoping to find a gene that would mutate into something new and possible get the part of the population that didn’t have the gene to develop something like it. What they found instead was again the only things that survived were those that previously were related to this string of weeds that I already had the gene So yes it’s evolution and the commonsense logic that things that are equipped with the right stuff are going to survive (But what about the stuff that manages To survive without the right stuff because they managed to change their behavior, Again this is explained by Darwinian evolution as they would have the right stuff to change their behavior) But natural selection didn’t produce anything new it was already there, it just was filtered out more. And Darwinian evolution wants to produce something new something entirely new using its principles. This would be ultimate proof that it was correct Now what a proponent of intelligent design would say was how did that gene get there in the first place how was it designed in But to be terribly honest with you I think intelligent design is evolution with teleology and a watchful creator, there is something there Darwinian evolution is affectively the exact same thing except there’s nothing there and mindless natural selection that doesn’t technically exist to act upon anything And when you lay it out it looks like the glass is half full versus the glass is half empty AaronS1978
Brother Brian:
Darwinian evolution at its very core just needs two things.
Three. 1- Fecundity 2- Inheritance 3- happenstance variation ET
AaronS1978, Darwinian evolution at its very core just needs two things. A source of variation and differential survival based on this variation. When Darwin was alive, he didn’t know about genetics and DNA. Early in the research it was thought that mutations were the source of this variation. And, in an ultimate sense, they still are. But we now know that there are many additional means of increasing variation (transpositions, inversions, sex, HGT, viruses, etc). The selection part requires multiple generations. I didn’t read this paper but from my brief scan of the OP it appears that they were looking at seeds (one generation) and expecting stresses on the seeds to cause mutations that result in resistance. If that is the case (and I admit that I could be wrong) then wouldn’t we expect any resistance in the population to have already existed? Brother Brian
All above, if I were a lawyer defending Darwinism in court, I would not want to rely on pre-existing traits, a feature just as easily explained in itself - by ex nihilo creationism. If ONLY I could have found evidence that new traits arose naturally from my millions of variations instead. News
Brother Brian:
Selection acting on existing genetic variation is a Darwinian process.
If and only if said genetic variation was a happenstance occurrence. Also natural selection, a process of elimination, doesn't act on anything. NS is nothing more than contingent serendipity. ET
I don’t believe anybody’s going to argue that this is a textbook example of evolution That’s not what this is being used for It’s just pointing out that it was a gene that already previously existed and it was marginally tweaked in some cases to produce the new affect and it is even then that possible new affect might always have existed A lot of this argument relates to the idea that micro evolution does not lead to macro evolution and I don’t believe anybody argues against microevolution So in this case the weeds already have the resistance built into their DNA Now the weed survives and then passes the trait on. But I believe the point is, that the trait was already there I think the problem is the comment that was brought up by BB was too vague and too simplistic and made an immediate claim that can be immediately argued without explaining why it’s supported the other side’s point of you. Now the argument is whether or not multiple micro changes to somethings DNA can actually lead to entirely new macro changes which would produce a new Species. This is where the real debate begins between evolution and intelligent design because there aren’t any real macro changes that lead to a new species that has been shown even in the world of bacteria has billions and billions of generations can be grown in a single shot and yet no new species comes of these billions and billions of generations. But I don’t prescribe the Darwinian evolution, I do prescribe to evolution with a dash of teleology and that life has a lot more control over its evolution then what Darwin said it did. Natural selection is just common sense, of course things better suited to its environment will survive, but I think the real stars of the show is life itself AaronS1978
Ah so, all. But they weren't getting new mutations producing resistance; just old stuff kicking in. For all anyone knows, the plants have had these defenses for a very long time. If I wanted to demonstrate Darwinism in action, I'd certainly have preferred that the new ones would work. News
Darwinian process just isn’t happening...
The Darwinian process is the differential reproduction of heritable variation. This study is about (pre-existing) genetic (heritable) variatnts that survive and reproduce better than others. It's pretty much a textbook Darwinian process. Mimus
Hazel, yes, there are plenty of examples of antibiotic resistance developing where it didn’t exist before. It is easiest demonstrate with bacteria because of the short generation time and you can start with a colony developed from a single cell, thus ensuring that the resistant gene didn’t pre-exist somewhere in the population There was a great example (maybe the one you referenced, but I can’t be sure) where they created a great slab of nutrient agar that had no agar at one end and then several clear delineations where antibiotics were added at increasing concentrations. In this way they were able to map the genome as the bacteria slowly spread across the slab. Brother Brian
I don't pay much attention to this kind of stuff, and certainly don't a biochemistry background, but this looks pertinent to the discussion. https://www.forbes.com/sites/jvchamary/2019/05/29/evolution-antibiotic-resistance/#661a51467646 hazel
It sounds as though the necessary evolution occurred a long time ago and that a Darwinian process just isn’t happening.
Selection acting on existing genetic variation is a Darwinian process. Brother Brian

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