A GT-seq panel for walleye (Sander vitreus) provides a generalized workflow for efficient development and implementation of amplicon panels in non-model organisms.

Abstract

Targeted amplicon sequencing methods, such as genotyping-in-thousands by sequencing (GT-seq), facilitate rapid, accurate, and cost-effective analysis of hundreds of genetic loci in thousands of individuals, but studies describing detailed workflows of GTseq panel development are rare. Here, we develop a dual-purpose GT-seq panel for walleye (Sander vitreus) and discuss trade-offs associated with different development and genotyping approaches. Our GT-seq panel was developed using restriction site-associated DNA data from 954 individuals sampled from 23 populations in Minnesota and Wisconsin, USA. We then conducted simulations to test the utility of loci for parentage analysis and genetic stock identification and designed 600 primer pairs to maximize joint accuracy for these analyses. We conducted three rounds of primer optimization to remove loci that overamplified and our final panel consisted of 436 loci. Optimization focused on reducing variation in amplification rate among loci and minimizing the proportion of off-target sequence, both of which are important considerations for developing large GT-seq panels. We also explored different approaches for DNA extraction, multiplexed polymerase chain reaction (PCR) amplification, and cleanup steps during the GT-seq process and discovered the following: (1) inexpensive Chelex extractions performed well for genotyping, (2) the exonuclease I and shrimp alkaline phosphatase (ExoSAP) procedure included in some current protocols did not improve results substantially and was likely unnecessary, and (3) it was possible to PCR amplify panels separately and combine them prior to adapter ligation. Well-optimized GT-seq panels are valuable resources for conservation genetics and our findings should aid in their construction in myriad taxa.