Fresh thinking on genetics could help trout breeders
A new approach to genetic evaluation could help commercial trout breeding programmes overcome one of their key challenges – how to assess the performance of sterile triploid fish.
Research by genetic experts at breeding and genetics business Troutlodge and Hendrix Genetics, part of the Troutlodge group, has found a way to assess the genetic performance of “triploid” fish – individuals which have three rather than two chromosomes.
Triploid trout are widely farmed because they are sterile, preventing early sexual maturation and protecting wild populations from genetic interbreeding. Triploidism is artificially induced as part of the breeding programme.
For broodstock, however, commercial breeding programmes need fertile, diploid broodstock with the regular two sets of chromosomes.
The problem arises when trying to evaluate the performance of triploid stocks in a real-world environment and correlating that with the diploid breeding programme.
Traditional BLUP (Best Linear Unbiased Prediction) genetic evaluations rely on standard pedigree-based relationship matrices, which assume uniform diploidy and miscalculate genetic relationships and variances when applied across different ploidy levels.
In standard (“ploidy-blind”) baseline models, estimated breeding values (EBVs) for triploid traits in diploid candidates suffered from up to 21% bias.
The Troutlodge researchers have developed a methodology applicable to breeding programs that enables:
- Improved selection accuracy for broodstock
- Integration of triploid data without distorting evaluations and
- Optimised genetic progress in key production traits.
The work was developed in collaboration with specialists from Hendrix Genetics/Troutlodge and Wageningen University & Research.
The findings were presented at the World Congress on Genetics Applied to Livestock Production (WCGALP), held July 11–17 in Madison, Wisconsin, by Dr. Katharina Correa, geneticist in the Salmonids Business Unit and part of the team supporting Troutlodge operations in Chile.
By eliminating EBV bias, breeding programs can select diploid broodstock candidates with higher accuracy based on the real performance of their triploid sibs in commercial settings.
Also, commercial farms using this methodology would not need to separate or exclude triploid phenotyping data; instead, the data can be fully utilised using modified relationship matrices without distorting genetic evaluations.
"Accounting for Different Ploidy Levels in Trout Genetic Evaluations in a Commercial Breeding Program" Marco Bink et al
World Congress on Genetics Applied to Livestock Production Digital Archive
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