Submitted to: Cryobiology
Publication Type: Abstract Only
Publication Acceptance Date: 7/29/2002
Publication Date: 7/29/2002
Citation: Richards, C.M., M. Antolin, and C. Walters. 2002. Maintenance of genetic variability in a cryopreserved population of Zizana texana embryos. 39th Meeting of the Society for Cryobiology, July 28-31, 2002, Breckenridge, Colorado. p. 145.
Interpretive Summary: The goal of genebanks is to preserve the genetic integrity of a sample. Some mortality is expected when germplasm in placed in cryostorage and so there are risks of genetic changes (bottlenecks). It is important to know the mechanism of the genetic change - via selection or drift- in order to design protocols that effectively maintain germplasm. This study used a small population of an endangered plant species, Zizania texana, to study the risk and mechanism of genetic bottlenecks when embryos are cryopreserved. Our results suggest that genetic changes during cryopreservation are random. This will enable us to develop better sampling and storage protocols for ex situ conservation of valuable genetic resources.
Technical Abstract: Embryos of the endangered plant Zizania texana are recalcitrant, but can be cryopreserved by a combination of exogenous application of cryoprotectants and rapid cooling in sub-cooled liquid nitrogen. This treatment yields 60 to 70% survival. To determine whether the 30-40% mortality resulting from cryo-exposure caused genetic changes through selection, we compared allelic frequencies within a heterogenous population of embryos before and after cryopreservation. Microsatellite markers from 5 unlinked loci were highly polymorphic (28 alleles total) and give a general indication of the genetic diversity of the population. There were no marked changes in allelic frequencies of the population of embryos surviving cryo-exposure, demonstrating that mortality of individuals was random (i.e. no selection). These data will be used to develop models of genetic erosion during ex situ conservation that consider the degree of initial heterogeneity and the risk of losing rare alleles through genetic drift in small populations of cryopreserved germplasm.