Detection Of QTL and eQTL with effects on osmoregulation capacities in the rainbow trout (Oncorhynchus myhiss)

There is increasing evidence that the ability to adapt to seawater in teleost fish is modulated by genetic factors. Most studies have involved the comparison of species or strains and little is known about the genetic architecture of the trait. To address this question, we searched for QTL affecting osmoregulation capacities after transfer to saline water in a nonmigratory captive-bred population of rainbow trout. A QTL design (5 full-sib families, about 200 F2 progeny each) was produced from a cross between F0 grand-parents previously selected during two generations for a high or a low cortisol response after a standardized confinement stress. When fish were about 18 months old (near 204 g body weight), individual progeny were submitted to two successive hyperosmotic challenges (30 ppt salinity) 14 days apart. Plasma chloride and sodium concentrations were recorded 24h after each transfer. After the second challenge, fish were sacrificed and a gill index (weight of total gill arches corrected for body weight) was recorded. The genome scan was performed with 196 microsatellites and 85 SNP markers. Unitrait and multiple-trait QTL analyses were carried out on the whole dataset (5 families) and eQTL detection on a part of this design (192 individuals from 3 families) using a custom 15k Agilent trout microarray, through interval mapping methods with the QTLMap software.