Maternal and paternal influence on early embryonic survival of androgenetic rainbow trout (Oncorhynchus mykiss): Implications for measuring egg quality

Breeding programs may have the unintended consequence of elevating levels of inbreeding; mutations unmasked through inbreeding may have deleterious effects on salmonid population viability. We used induced all-paternal inheritance (androgenesis) to assess the incidence of mutations affecting early development in rainbow trout (Oncorhynchus mykiss) and to provide insights into the genetic basis for inbreeding depression. Assays conducted on androgenetic haploid embryos derived from four rainbow trout populations allowed us to test whether a homozygous clonal line produced in our laboratory had been purged of deleterious alleles affecting early embryonic development. Assays showed no significant difference in viability of androgenetic haploids produced from clonal or outbred lines of rainbow trout during early development. These results are not consistent with the dominance hypothesis of inbreeding depression, which attributes inbreeding depression primarily to expression of deleterious recessive alleles. However, significant maternal effects on haploid embryo viability were identified, implying that egg quality may have a larger effect than paternally inherited deleterious recessive alleles on early haploid embryonic development. Androgenetic haploid assays may thus be useful as a stringent measure of egg quality in aquaculture breeding programs.