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.