Use of secondary somatic embryos promotes genetic fidelity in cryopreservation of cocoa (Theobroma cacao L.)

Abstract

The inability to conserve cocoa (Theobroma cacao L.) germplasm via seed storage and the vulnerability of field collections make the establishment of cryopreserved genebanks for the crop a priority. An effective encapsulation-dehydration based cryopreservation system has been developed for cocoa but because the somatic embryos used for freezing arise after a protracted period of callus culture there is concern about maintenance of genetic fidelity during the process. Microsatellite markers for seven of the 10 cocoa linkage groups were used to screen a population of 189 primary somatic embryo-derived emblings and the 43 secondary somatic embryos they gave rise to. Of the primary somatic embryos, 38.1% exhibited polymorphic microsatellite profiles while for secondary somatic embryos the frequency was 23.3%. The same microsatellite markers used to screen another population of 44 secondary somatic embryos cryopreserved through encapsulation-dehydration revealed no polymorphisms. Scanning electron microscopy showed the secondary somatic embryos were derived from cotyledonary epidermal cells rather than callus. The influence of embryo ontogeny on somaclonal variation is discussed.

Meristem micropropagation of cassava (Manihot esculenta) evokes genome-wide changes in DNA methylation

“…However, deciphering global hyper/hypomethylation from restriction products is not a reliable approach ( Fulneček and Kovařík, 2014 ). What is more, other studies have shown that methylation levels during in vitro propagation are related to the donor tissue ( Fang et al, 2009 ; Wang et al, 2012 ), to the length of the culture ( Diaz-Sala et al, 1995 ; Rodríguez López et al, 2010a , b ), and the media components ( LoSchiavo et al, 1989 ; Arnholdt-Schmitt, 1993 ).…”

Epi-fingerprinting and epi-interventions for improved crop production and food quality

“…The ability to propagate elite or desirable clones is an essential part of the seed production industry. The advent of reliable in vitro systems for the replication and regeneration of plant materials has led to their widespread deployment for propagation ( Bertrand et al, 2011 ; Etienne et al, 2012 ), germplasm conservation ( Fang et al, 2009 ), and breeding purposes ( Henry, 1998 ), as well as for more fundamental research on model species ( Berdasco et al, 2008 ; De-la-Peña et al, 2012 ; Moricová et al, 2013 ). For micropropagation and genetic transformation systems to be efficient, it is necessary that the plants recovered from them are genetically and epigenetically faithful to the original stock material.…”

Effect of cryopreservation and post-cryopreservation somatic embryogenesis on the epigenetic fidelity of cocoa (Theobroma cacaoL.)

“…Not surprisingly, our results showed an increase in variability in all in vitro cultured samples ( in vitro , 1h LN, Post 1h LN). As we have shown previously, this variability is both genetic and epigenetic in nature [12,14–16,36]. More interestingly, SSE recultured after one hour in liquid nitrogen (i.e.…”

“…However, the passage of cells through in vitro culture [11] and cryopreservation [35] may lead to undesirable changes (somaclonal variation) in the regenerants. Although the effect of in vitro culture, somatic embryogenesis and cryopreservation of somatic embryos on the morphological and genetic fidelity of cocoa plants has been extensively studied [12,14–16,36], very little is known about the epigenetic modifications introduced by the cryopreservation of cocoa somatic embryos. Not surprisingly, our results showed an increase in variability in all in vitro cultured samples ( in vitro , 1h LN, Post 1h LN).…”