Hybrid linkage group RYHyb20 showing the fusion between rainbow trout chromosomes Omy20 and Omy28. Female- and male-merged hybrid maps are shown. The grey shaded area represents a block of non-recombining loci spanning the p-arm, centromere, and q-arm of Omy20 and the acrocentric Omy28. The fusion between the Omy20 and Omy28 homologues in a male Yellowstone cutthroat trout (YCT) map, identified by applying four loci in common to the hybrid and rainbow trout maps, is also shown. The rainbow trout chromosome (Omy), linkage group (RT), and chromosome arm (p, q) or centromere (c) location for each locus mapped in rainbow trout by Guyomard et al. (2006) and Rexroad et al. (2008) is indicated. Map distances are in centiMorgans.