[b said:
Quote[/b] ]I'm saying hundreds of thousands of genetically identical plants grown throughout the world since 1996 and none of which have shown any mutation would lessen the chances of one of these plants mutating, as opposed to batches of genetically different plants grown from seed.
None of which have shown *visible* mutant phenotypes, that we know of. Most mutations either have little effect or are invisible, affecting things such as metabolic pathways.
Additionally, plants are usually diploid (I'm excluding mosses and ferns here, which have both haploid and diploid stages), and plants have an usual talent for aneuroploidy and full-blown polyploidy. This means that any given gene exists in a minimum of 2 copies in the genome, possibly many more. If one is rendered non-functional or its function is altered by mutation, the other copy 'fills in' and covers up the mutation. In sexually reproducing species, these mutations would be expressed down the line when an individual inherited two copies of the same original mutant allele. In asexual species (or those propagated strictly asexually), the mutation will not be expressed until a second mutation of the same sort occurs on the other gene; the probability of this happening is very small.
In fact, since aseuxally reproduced plants don't have the genetic shuffling that goes along with sex, I'd suspect they'd actually have a higher-than-usual number of hidden, novel mutations, because without that genetic shuffle, such mutations *remain* hidden, while in sexually-reproduced plants, the mutations become expressed via offspring that are homozygous for the mutant allele, and thus are exposed to selection, either positive or negative, leading to the elimination or fixation of the mutant allele.
The diversity of offspring seen as a result of sexual reproduction isn't due to any higher mutation rate (male germ line cells do have a higher mutation rate in vertebrates, but not to a tremendously significant level), but rather due to 'shuffling the genetic deck' bringing new combinations of existing genes to the light.
If asexual reproduction was any real barrier to mutation, we wouldn't have to worry about antibiotic-resistant bacteria. And while plants are, to an extent, different from bacteria, they aren't really that different at the molecular level (in fact, all life is more or less the same at the molecular level, with large differences only appearing between groups separated by billions of years of evolution). DNA is DNA, and regardless of how it's copied, there *will* be errors.
Mokele