Introduction. The cryopreservation of chicken sperm is well mustered in France. Until recently, this was only existing tool for the conservation of avian genetic resources. However, this method has two limitations: i) it does not allow the conservation of the genetic resources of female birds linked to the specific sex chromosome W; ii) restoring the genotype using frozen semen requires several backcrosses and take several years. In this context the cryopreservation of diploid primordial germ cells (PGCs) collected from the early embryo and amplified in vitro is of great interest as a conservation strategy complementary to the sperm-based biotechnology. After thawing and re-amplification in vitro PGCs can be transplanted in a recipient embryo, where they can develop to functional gametes and give offspring (van de Lavoir et al., 2006, Whyte et al., 2015). Using this process alone or in combination with the use of frozen semen would restore the male and female genotypes of interest in a single generation. Objectives. In CRB ANIM project and projects in connection with the latter (VALBIODI, region Centre and IMAGE, H2020) the objectives were i) to develop a complete system for the conservation and restoration of chicken genetic resources based on PGCs, using as a model a local endangered breed "La Noire du Berry” (NB); ii) to understand the impact of the in vitro steps (culture and cryopreservation) on the molecular and physiological aspects of the quality of PGCs in both sexes by "omic" and in vivo approaches; iii) to enrich the collection of avian national cryobank by the male and female NB PGCs samples. Results. We developed, cryopreserved and cryobanked cultures of PGCs NB. We investigated the molecular properties of PGCs in the in vitro environment using high throughput approaches. This study revealed an important sexual dimorphism of PGCs derived in culture, despite their presumed undifferentiated germ stem cells state. Proteomic LC-MSMS and transcriptomic RNAseq studies showed important differences in protein and transcript abundance between male and female PGCs that suggest their early autonomous sexual determination, which may be responsible for described previously sexual differences in their behavior in culture and in vivo. The study of DNA methylation showed that culture duration and cryopreservation significantly affected the epigenetic landscape of PGCs. This impact was stronger on the methylome of male PGCs than on that of females. The sexually dimorphic effect of culture duration was also observed on the transcriptome. In contrast, cryopreservation had little effect on gene expression in both sexes. To evaluate the reproductive capacity of conserved PGCs NB, we created germline chimeras by injecting thawed and reamplified in vitro PGCs NB in Rhode Island embryos. Reproduction of these chimeras resulted in germline transmission rate of up to 60.6% for female PGCs NB and up to 42.4% for male PGCs NB. These results demonstrate the efficiency of the developed PGCs biotechnology and well conserved reproductive potential of in vitro derived cryopreserved PGCs . The transmission rate seams to vary according to the culture duration in a gender-specific manner. Perspectives. The integration of the obtained data will allow to understand the molecular mechanisms impacted in the PGCs by the in vitro steps. This knowledge will be useful to better adapt these steps to the physiology of PGCs and improve their quality.