|REVILLA, M. ANGELES|
Submitted to: Agricultural Food and Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2009
Publication Date: 9/14/2009
Citation: Peredo, E.L., Arroyo-Garcia, R., Reed, B.M., Revilla, M. 2009. Genetic Stability of In Vitro Conserved Germplasm of Humulus Lupulus L.. Experiment Station Bulletins. 18(2):144-151(8).
Interpretive Summary: The genetic resources of hops are preserved as field plants and backed up for safety as tissue cultures in cold storage, or as cryopreserved shoot tips. This study was to determine if genetic changes occur with these procedures. Three hops cultivars were analyzed for genetic change after tissue culture, cold (45 °F) storage, and cryopreservation in liquid nitrogen (-320 °F). No genetic changes were noted but there were changes in gene expression. Most of this variation could be related to the cold storage or cryopreservation protocols. The pattern of change could be explained by temporary changes related to the cold acclimation step present in both treatments. Cold acclimation is a complex process, achieved by short day length and low temperatures, which results in the reprogramming of metabolism and gene expression. The amount of variation detected is similar for cold-stored (2.6 to 8.6%) or cryopreserved (2.6 to 9.8%) hops. Similar changes were reported in cryopreserved apple and strawberries and citrus callus under slow growth conditions. Cold acclimation was not used prior to the storage protocols for any of these studies.
Technical Abstract: The genetic and epigenetic stability of hop accessions after being cryopreserved for one year or cold stored for three years were evaluated using several molecular markers (RAPDs, AFLPs and MSAPs) and clear, repetitive and specific patterns were obtained among accessions and between control and treated samples. Although no genetic changes were detected with RAPDs and AFLPs markers between control potted plants grown in a screened house and in vitro plants regenerated from slow-cooling cryopreserved shoot tips or cold stored in vitro shoots, MSAP analysis detected methylation changes in a 36% of the loci. Nevertheless, only 2.6 to 9.8 of the detected changes could be ascribed to the conservation procedure and most of them seemed to be generated during the in vitro culture. Due to the amount of accessions (51) analysed we can assume that hop genotypes have similar behaviour when cryopreserved or cold stored, so both protocols are suitable of being used as standard storage methods, but it is important to take into account the epigenetic changes produced during the process.