Somaclonal variation among somatic embryo derived plants — Evaluation of agronomically important somaclones and detection of genetic changes by RAPD in Cymbopogon winterianus

• The present research work is actually a continuation of our previous work published in 2010 (Dey et al., 2010a). On that article we have reported the obtained results related to somatic embryogenesis from C. winterianus. Therefore, this article is started with the objective to generate roots from the regenerated plants.
• Second focus of the present study was to formulate the hardening protocol of the plantlets and ex vitro establishment of the plantlets to the soil. From the 14 embryogenic callus derived plantlets we have established 79.73% plantlets in the green house and after transferring of these plantlets to the field a total of 105 plants were survived.
• We have highlighted the present study for screening and selection of somaclonal variants of C. winterianus based on agromorphological and chemical characters. After careful screening primarily a total of 10 superior somaclones were selected on the basis of results of initial screening and replicated trial (RBD).
• Then we have tried to assess the relative stability of 10 superior somaclones which retained improved oil content and quality in initial screening and replicated trial and only five somaclones maintained relative stability for the main selected traits up to 4th clonal generation of the 2nd year.
• Final objective is to report the RAPD analysis of selected superior somaclones of C. winterianus to access the similarity/dissimilarity at DNA level. Our obtained results indicate that gross genetic changes do occur in long term tissue culture regenerants and RAPD can be more effective in accessing the in vitro regenerants to select superior somaclones.

A total of one hundred five plants of Cymbopogon winterianus derived from indirect somatic embryogenesis were established in the field. Extensive somaclonal variation was noticed within these plants for all eight agronomic characters such as plant height, diameter of bush, number of tiller/clump, number of leaves/clump, leaf length, leaf breadth, weight of 100 leaves and oil content in relation to the donor parent. Significant variations were also recorded for two major constituents of essential oil such as citronellal and geraniol in some selected somaclones. Ten somaclones that were retained improved oil content and quality in initial screening and, in a replicated trial, were further assessed for their stability in the field for four clonal propagations. Out of the ten superior somaclones only five superior somaclones (SC1, SC2, SC3, SC6 and SC10) which showed relative stability both in oil content and quality were subjected to random amplified polymorphic DNA (RAPD) analysis. Out of the eighteen primers used, ten primers revealed polymorphism showing distinctly different banding patterns in the five improved somaclones, which were equally prominent in their differences from the control. Out of the 44 polymorphic bands, 30 were parental bands which were missing from some somaclonal progenies and 14 were novel non-parental bands which were detected only in some somaclones that confirmed the presence of genetic changes due to somaclonal variation.