Genetic basis of the variegated tail pattern in the guppy, Poecilia reticulata

Abstract

Variegated patterns on the caudal fin are a common and popular trait in guppy strains commercially cultured in Singapore. Gene control of this highly variable mosaic pattern of black spots and patches of different shapes and sizes on a brightly colored tail fin was elucidated by reciprocal crosses between the Green Variegated (GV) strain and wild-type (WT) stock. F1 progenies were produced by single-pair crossing between GV and WT, while the F2 generation was obtained from full-sib mating between F1 males and F1 females. Data for the F1 and F2 generations were segregated according to phenotypes and sex, and tested by chi-square analyses. Inheritance of variegated tail patterns appears to be determined by a single locus on the X-and Y-chromosomes. Genotypes of males and females of the GV strain are proposed to be XVarYVar and XVarXVar, respectively. The allele for variegated tail patterning, Var, is dominant over that of the wild-type, Var+, which does not exhibit these patterns. Recombination frequency between the Var locus and sex-determining region (SdR) in male guppies was estimated to be about 1.9% (map distance ≈ 1.9 map units). The segregation and mode of inheritance of the Var gene are illustrated by genetic models.