Diversity analysis, runs of homozygosity and genomic inbreeding reveal recent selection in Blanco Orejinegro cattle.

Abstract

Blanco Orejinegro (BON) cattle have 500years of adaptation to the Colombian tropic, but little is known about their genetic history. Our aim was to estimate levels of linkage disequilibrium (LD), effective population size (Ne), genomic inbreeding for runs of homozygosity (FROH ), genomic relation matrix (FGRM ), excess of homozygotes (FHOM ) and pedigree information (FPEDCOMP ) and to characterize the runs of homozygosity (ROH), searching for selection signatures. A total of 419 BON animals were genotyped, 70 with a 150K chip and 349 with a 50K chip. Next, an imputation to 50K was performed, and, after editing, databases of 40K were obtained. The PLINK v1.90 and R programs were used to estimate LD, ROH, FROH and FHOM . The SNeP v1.1 program was used to obtain Ne, and PreGSf90 was used to elaborate the scaled G matrix. The MTDFNRM program was used to estimate FPEDCOMP . The LD mean as r2 at 1Mb was 0.21 (r2 >0.30 at a distance of 96.72kb), and Ne was 123±1. A total of 7,652 homozygous segments were obtained, with a mean of 18.35±0.55 ROH/animal. Most of the genome was covered by long ROHs (ROH>8 Mb =4.86%), indicating significant recent inbreeding. The average inbreeding coefficient for FPEDCOM , FGRM , FHOM and FROH was 4.41%, 4.18%, 5.58% and 6.78%, respectively. The highest correlation was observed between FHOM and FROH (0.95). ROH hotspots/islands were defined using the extreme values of a box plot that was generated, and correspond to QTLs related to milk yield (55.11%), external appearance (13.47%), production (13.30%), reproduction (8.15%), health (5.24%) and meat carcass (4.74%).