New QTL for resistance to Salmonella carrier-state identified on fowl microchromosomes

Abstract

Chicken's ability to carry Salmonella without displaying disease symptoms leads to an invisible propagation of Salmonella in poultry stocks. Using chicken lines more resistant to carrier state could improve both animal health and food safety. Previous studies identified several QTL for resistance to carrier state. To improve genome coverage and QTL detection power we produced a new set of 480 informative SNP markers and genotyped a larger number of animals. Ten additional microchromosomes could be covered when compared with previous studies. These new data led to the identification of 18 QTL significant at the chromosome-wide level. The only QTL significant at the genome-wide level were identified on microchromosomes 14 and 22 and have never been identified previously. Using a higher number of animals improved the power and the precision of QTL detection. Some of the QTL newly identified are located close to candidate genes or microsatellite markers previously identified for their involvement in the genetic control of resistance to Salmonella, which confirms their interest for selection purposes.

A maximum likelihood QTL analysis reveals common genome regions controlling resistance to Salmonella colonization and carrier-state

“…Nevertheless, in our last genome scan performed with QTLExpress, an effect nearing significance could be observed on chromosome 3. In addition, our earliest QTL analyses identified a QTL on chromosome 2 [2,3], although it was not confirmed in our last SNP genome scan [4]. …”

“…Until now, none of the QTLs controlling carrier-state has been identified close to those QTLs for resistance to colonization or systemic salmonellosis. This is why it was hypothesized that the genetic controls of Salmonella carriage and colonization were independent [2]‐[4]. Nevertheless, in our last genome scan performed with QTLExpress, an effect nearing significance could be observed on chromosome 3.…”

“…Two of these QTLs, on chromosomes 2 and 16, were confirmed in a subsequent analysis including all animals, while those on chromosomes 1 and 16 were replicated in an independent population of a commercial line of laying hens [3]. More recently a new, more powerful QTL analysis was carried out [4], using a higher number of animals genotyped with a higher number of markers (480 SNPs). Using this approach, we were able to perform a more extended genome scan which resulted in the identification of novel QTLs on several microchromosomes, not previously covered in other analyses.…”

“…With this software it was also possible to evaluate different QTL effects between sire families, to test the co-existence of two QTLs and to analyze discrete data. For these analyses we used the same data as previously described [4], i.e. 480 SNP genotypes for 378 animals already phenotyped.…”

Integrated Genomic Approaches to Enhance Genetic Resistance in Chickens

“…Many QTL regions associated with resistance to Salmonella carrier state, antibody response, or salmonellosis have been identified through genome scans located widely throughout the genome (69,77,(111)(112)(113)(114). This large QTL number supports the highly polygenetic nature of the host response, but QTLs with effects as large as 37% of the phenotypic variance in carrier state have been identified (111).…”