Gargan, L. M. | Search bioRxiv

bioRxiv2021

Comparative analysis of single nucleotide polymorphisms and microsatellite markers for parentage verification and discovery within the equine Thoroughbred breed

Short tandem repeat (STR), also known as microsatellite markers are currently used for genetic parentage verification within equine. Transitioning from STR to single nucleotide polymorphism (SNP) markers to perform equine parentage verification is now a potentially feasible prospect and a key area requiring evaluation is parentage testing accuracies when using SNP based methods, in comparison to STRs. To investigate, we utilised a targeted equine genotyping by sequencing (GBS) panel of 562 SNPs to SNP genotype 309 Thoroughbred horses - inclusive of 55 previously parentage verified offspring. Availability of STR profiles for all 309 horses, enabled comparison of parentage accuracies between SNP and STR panels. An average sample call rate of 97.2% was initially observed, and subsequent removal of underperforming SNPs realised a pruned final panel of 516 SNPs. Simulated trio and partial parentage scenarios were tested across 12-STR, 16-STR, 147-SNP and 516-SNP panels. False-positives (i.e. expected to fail parentage, but pass) ranged from 0% for 147-SNP and 516-SNP panels to 0.003% when using 12-STRs within trio parentage scenarios, and 0% for 516-SNPs to 1.6% for 12-STRs within partial parentage scenarios. Our study leverages targeted GBS methods to generate low-density equine SNP profiles and demonstrates the value of SNP based equine parentage analysis in comparison to STRs - particularly when performing partial parentage discovery.

genetics↗

bioRxiv2019

Environmental (e)DNA detection of the invasive pink salmon Oncorhynchus gorbuscha during the 2017 Norwegian invasion

The pink salmon Oncorhynchus gorbuscha was introduced from its native range in the Pacific to Northwest Russia several times since the 1950s. While this species has been regularly observed in rivers in Northern Norway since that time, there has been an upsurge in the numbers of odd-year O. gorbuscha individuals observed in rivers in southern Norway in recent years, and particularly in 2017. Although the wide-scale effects of this species presence are currently uncertain, there are concerns regarding potential competition between O. gorbuscha and native species - most notably the Atlantic salmon Salmo salar. Environmental (e)DNA is becoming a widely used tool to monitor rare and invasive species in aquatic environments. In the present pilot study, primers and a probe were developed to detect O. gorbuscha from eDNA samples taken from a Norwegian river system where the species was observed. Water samples were taken at both upstream and downstream locations of the Lysakerelva river during Autumn 2017 (to coincide with spawning) and during late Spring 2018. Autumn samples were positive for O. gorbuscha at both sampling locations, whereas Spring samples showed positive detection of this species in the upstream region of the river, when smolt should have left, or be in the process of leaving the river. These findings reveal that eDNA-based methods can be used detect the presence of O. gorbuscha during their spawning season. This suggests that odd-year populations have the potential to become established in the studied river system. We recommend that eDNA sampling is repeated to determine whether individuals of this odd-year population have survived at sea and return to spawn. Our assay specificity tests indicate that the tools developed in the present study can be used for detection of O. gorbuscha in both Norwegian and other European river systems where presence/absence data is required. We also suggest some modifications to our methodology that may improve upon the detection capabilities of O. gorbuscha using eDNA.

genetics↗