Blog entry 1: Are micropropagated plants genetically identical and stable?

Plant tissue culture or micropropagation has become a very important method to regenerate genetic identical clones of a plant in vitro and can result in preserving valuable genetic resources of threatened species. A problem in this process can be somaclonal variation among the clones. 

Picture 1: in vitro propagation of an orchid (B.Giger, 07.03.17)

The conventional way to prove the true-to-type nature of a clonal plant

RAPD (randomly amplified polymorphic DNA) and ISSR (inter simple sequence repeat) are the conventional methods to analyse the genetic stability of the generated plants. In these processes, the genomic DNA of the donor plant and the in vitro raised plants are compared to each other. (Saha et al., 2016)

Mass propagation of Gloriosa superba as a promising technique

The colchicine alkaloid contained in the tubers and seeds of G. superba has medical features and is antimitotically active. Due to the various usage, the plants containing colchicine are being exploited by many parties. This over-exploitation combined with the poor propagation of G. superba and its sensitivity to many pests are threatening to the species. Through mass propagation, it is possible to generate numerous new individuals of the species in a short time and thus cover the high demand of the plant and possibly save an endangered species. Genetic fidelity is very important, because especially for commercial use the generated plants mustn’t show any unwanted variations but should rather be homogenous to guarantee a certain standard of quality. (Yadav, Aggarwal, & Singh, 2013)

Terms

somaclonal variants	Somaclonal variants have their origin in in vitro cell and tissue culture. Normally, when cells ore tissue is amplified, the goal is to generate clones identical to the original cells or tissue. However, there can occur spontaneous genetic variability in the cultured cells and therefore, there are differences shown among the clones. The variations can be phenotypic or genotypic. (Orton, 1982)
PCR and amplification	PCR is short for polymerase chain reaction. It is a method used to synthesize a new strand of DNA, which is complementary to the original strand. This is possible by using DNA polymerase, which can add nucleotides to already existing 3’-OH-groups with the help of a primer. In the end, the synthesized DNA sequence can be multiplied various times and therefore is an amplification of the pre-existing DNA strands. (NCBI, 2014)
Primer	As mentioned above, the primers are needed for the polymerase chain reaction. It leads the DNA polymerase to the right place on the template strand, where it can begin the synthesis of new DNA nucleotides from the end of the primer.(NCBI, 2014)
Genetic markers	Genetic markers are alleles, which produce visibly different phenotypes and therefore their presence in an organism can be easily detected. (Griffiths et al., 2000)

Is the proposed method save enough to prove genetic fidelity of clonal propagated plants?

The assessment of genetic stability of micropropagated plant like G. superba through RAPD and ISSR analysis provides important information for the successful propagation of genetically identical and stable plants for commercial use. (Yadav et al., 2013)

References

Griffiths AJF, Miller JH, Suzuki DT, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000. Mapping with molecular markers. Available from: https://www.ncbi.nlm.nih.gov/books/NBK21962/

NCBI. (2014). Polymerase Chain Reaction (PCR). Retrieved 10 March 2017, from https://www.ncbi.nlm.nih.gov/probe/docs/techpcr/

Orton, T. J. (1982). Somaclonal variation. California Agriculture, 8, 20–21.

Saha, S., Adhikari, S., Dey, T., & Ghosh, P. (2016). RAPD and ISSR based evaluation of genetic stability of micropropagated plantlets of Morus alba L. variety S-1. Meta Gene, 7, 7–15. https://doi.org/10.1016/j.mgene.2015.10.004

Yadav, K., Aggarwal, A., & Singh, N. (2013). Evaluation of genetic fidelity among micropropagated plants of Gloriosa superba L. using DNA-based markers — a potential medicinal plant. Fitoterapia, 89, 265–270. https://doi.org/10.1016/j.fitote.2013.06.009