**4. Genetic stability**

Maintenance of genetic fidelity is essential for a successful cryopreservation strategy [54] and requires tools for evaluating the genetic stability of conserved plants. Theoretically, during cryopreservation all metabolic activities stop at the ultralow temperature of LN, consequently, after rewarming from cryopreservation recovery of true-to-type plants is expected [55]. Cryopreservation protocols involve cooling in and rewarming from LN, *in vitro* culture and regeneration processes, phenotypic and genomic changes can occur due to somaclonal variation. Hence, it is necessary to verify true-to-type plants after cryopreservation [56]. The literature is overall 'positive' regarding the outcome of stability assessments from cryopreservation with studies. The various types of DNA markers detect different levels of polymorphism and different amounts of DNA change. Genetic stability is the norm in most studies of possible plant genetic variation following cryopreservation [56].

The development of molecular techniques in the recent year provides additional means for assessing genetic fidelity in plants. Single sequence repeats (SSRs) are tandemly repeated motifs of one to six bases present in coding and non-coding regions and are highly polymorphic [57]. *F*. x *ananassa* shoot tips were cryopreserved using encapsulation-dehydration and vitrification along with that new modified method cryoplate (V and D cryoplate) [48]. Plants raised through these techniques were subjected to genetic stability analysis using SSR markers. No differences were observed between *Fragaria in vitro* mother plants and *in vitro* cryopreserved plants using eight SSR primers [58]. This lack of variation suggests that there were no changes in the genetic fidelity of the plants due to cryopreservation. This was also the case in *Solanum*, in which the microsatellite sequences of plants regrown from cryopreserved apices were identical to the profiles of the parent plants and their progeny [59]. No structural changes were observed in the *in vitro* control or the Solanum plants grown from the cryopreserved germplasm, indicating stable inheritance of SSR sequences in the somatic progeny [59]. The low coverage of the genome is one criticism of molecular techniques. Despite being highly polymorphic and co-dominant, SSRs may be clustered and distributed unevenly in certain chromosome locations.
