I am trying to judge how, where and why the cryptic genetic variability arises in the course of propagation pathway using molecular markers. While doing the AMOVA I could find that there exists a higher distribution of genetic variation within the generations as compared to among the generations of micropropagated plants. I could find an identical report in wheat, the paper which I am attaching with this question http://link.springer.com/article/10.1007%2Fs11240-014-0525-1. Although they have reported identical phenomenon, but they have not given any explanation for the possible occurrence of this type of variability. What can be the reason?
How do you analyze genetic variability between generations? I took a quick look at the paper of Ramakrishnan and from what I can understand, the genetic variability between generations is analyzed between the mother plant and a group of plantlets regenerated thereof; while the variations within a generation (I suppose) includes all the genotypes... If this was the case, it makes perfect sense that you get greater variations within a generation which includes multiple genotypes, while genetic variation is very low between the mother plant and its regenerated plantlets, which mostly have the same genotype, except for somaclonal variation, which is supposed to contribute only to minor differences in genotype.
The mother plant and its "progeny" are supposed to have lower genetic variability because they share basically the same genotype. Within a generation you have multiple genotypes, and therefore, higher genetic variability.
Dear Paromik
In my opinion searching for the clues for occurrence of native variability in vegetatively propagated plants like orchids from a self pollinated and seed propagated crop like wheat is misplaced perception. The higher level of variability in naturally occurring population of orchids is a cumulative effect of genetic variability that is build up with time when the species is continuously multiplied through vegetative route (protocorms in case of orchids). Such a build up of variability spectrum in such plant species are mostly towards deterioation in genetic vigour and lower resistance against prevalent micro-flora in a given location. Absence of sexual reproduction prevents genetic recombinations and hence regular up-gradation of plants' genetic make up. In case of micropropagated generation of orchids, the level of variations is low because most of the propagules are originated from limited number of cells of single genotypes unless we deliberately create selection pressure to select a variant phenotype.
Hope I have clarified your query to some extent. Please revert back for further discussion on this important question
AK Mathur
Dear Mathur Sir,
You truly answered my query. Thank you very much.
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