With the application of Genomic Selection techniques, Hendrix Genetics has found a way to improve the resistance of salmon to Salmon Rickettsial Syndrome (SRS).
SRS is a huge problem for the Chilean Atlantic salmon industry, responsible for annual production losses of more than $100 million. The R&D team of Hendrix Genetics has performed an extensive disease challenge test where preliminary estimations indicate an improvement in the range of 17 – 23 percent reduction in mortality rates.
Instead of focusing on a limited number of QTL’s – specific parts of the genome that influence a quantitative trait – the R&D team of Hendrix Genetics uses Genomic Selection as with most traits, many genes in the DNA are coding for an effect on a quantitative trait. The Genomic Estimated Breeding Value (GEBV) for a particular animal in this context is the calculated sum of all these effects. Incorporating information on the whole genomic profile allows more accurately predictions of an animals’ breeding value, beyond just the use of QTLs. Based on the sum of effects, Genomic Selection proves to be much more effective in reducing mortality caused by SRS.
Mortality reduction
A disease challenge test was set up by researchers of Hendrix Genetics in cooperation with CORFO, the Chilean economic development agency of the Ministry of Economic, Development and Tourism. The test total population size was around 1500 fish. In the population three major QTL’s explaining resistance to SRS were found. 40 percent of the animals were carrying the QTL’s with the most favourable genotypes. Survival amongst this group was with 24 percent significantly higher than the average population (8.2 percent). This implies a reduction in mortality of around 17 percent. As such a more than significant result, when selecting on QTL’s.
Genomic selecton
The power of Genomic Selection for identification of the most resistant individuals is demonstrated by the enormous difference in recorded survival of fish in the challenge test predicted by ranking on GEBV. The 25 fish with the highest GEBV score a survival rate of 80 percent, compared to the background population (8.2 percent). When applying the outcome of this test to normal Chilean production circumstances, preliminary estimations result in a reduction in mortality in the range of 23 percent.
“The test results show enormous potential for the use of Genomic Selection,” says Robbert Blonk, Hendrix Genetics’ director of R&D.
