Role of new and current methods in semen technology for genetic resource conservation.

The establishment of repositories of frozen semen, for the conservation of agricultural genetic resources, is not a simple matter of collecting and freezing semen in the hope that one day it will be suitable for use in an artificial insemination procedure. Important genetic issues need to be considered; for example, how many samples should be stored and from how many individuals? Aside from these, many biological and logistic issues must be considered. Cryopreservation technology does not work equally well in all species, often because of anatomical differences in the female reproductive tract leading to significant variability in the number of spermatozoa needed in order to achieve an acceptable conception rate. Moreover, spermatozoa from different species are not equally susceptible to cryoinjury. However, it is also emerging that semen samples from individuals within a species are also of different quality; several studies have revealed that these differences reflect the quality of DNA within the spermatozoon itself and also the efficacy of biochemical functions, including metabolic and signalling systems, within individual cells. As new possibilities to select spermatozoa for insemination arise, especially the use of flowsorting for gender selection, these issues may become more significant. In this article we interpret the way in which some of this new information may impact upon the practical implementation of genetic resource conservation.