By: Jackie Walling
A study published in August 2017 in the Journal of Animal Science investigates the genetic variance of columnaris
disease (CD) associated with two rainbow trout populations. CD, also known as Cotton Mouth, is characterized by white/cloudy patches on the fish, frayed fins, skin ulcerations, rapid breathing, and lethargy. It is caused by Flavobacterium Columnare found in fresh water throughout the world. The intent of this study was to identify the genomic regions in rainbow trout likely responsible for explaining the majority of genetic variance of CD resistance.
Two populations were studied: National Center for Cool and Cold Water Aquaculture (NCCCWA) and Troutlodge, Inc. (TLUM
). Both provided pedigree records showing CD resistance (based on phenotype) in 15.5% of NCCCWA and 11.0% of TLUM
fish. Genotypes for 57k SNP were available for 1,185 of NCCCWA fish and 1,137 of TLUM
fish with the effects and variances of SNP estimated using the weighted single-step genomic BLUP approach which accounted for 1 Mb moving SNP-windows.
The NCCCWA saw a total of 13 windows located on six chromosomes. Two of those windows were found on chromosome Omy17 and were responsible for 12% and 11.33% of genetic variance pertaining to CD resistance. TLUM
had 16 windows on nine chromosomes. Limited resemblance existed between the two populations, but three similar windows were located on two chromosomes in both populations. Limited
similarity suggests the SNP windows are not enough information to fully explain genetic variation and CD resistance may be influenced by more than one gene. Previous generations of selective breeding for bacterial cold water disease resistance in NCCCWA fish may contribute to the differences found between the two populations. TLUM
has not undergone such extensive selection. Further research needs to be done to accurately prospect genomic regions associated with CD in rainbow trout.
To read the full abstract, visit the Journal of Animal Science.