Aspects of red and black color inheritance in the Japanese ornamental (Koi) carp (Cyprinus carpio L.)

Three color phenotypes were studied in koi: red color including its related patterns, black Bekko pattern (relatively small black spots) and black Utsuri pattern (large black patches). Three phenotypes were associated with the red color: transparent (colorless), Kohaku (red pattern) and completely red. Considerable variation was observed in the proportion of these phenotypes, among progeny of such parents. All cross-combinations involving Kohaku yielded progenies with certain proportions of Kohaku. All offspring were completely red in crosses between red parents, and red color was found in offspring of transparent parents. We suggest that a minimum of three genes, with inter- and intra-locus interactions, control the genetics of the red color traits. Crosses between two parents of the black Bekko pattern resulted in progeny having an average ratio of 3:1 (Bekko/non-Bekko). Crosses between Bekko and non-Bekko parents resulted in progeny having an average ratio of 1:1. We suggest that a single gene with a dominant effect of the black pattern allele controls the Bekko pattern. Utsuri koi were found only in progeny of Utsuri parents in variable proportions (0-16%), together with other dark-pigmented phenotypes (e.g. grey, wild-type color). Two distinct developmental stages of dark pigmentation (hatched-out larvae and about 14-day post-hatching) were associated with the Utsuri and the Bekko patterns, respectively. Probably different genes control the early development of the Utsuri and Bekko black patterns. We used microsatellite markers to screen pools of DNA from several phenotypes, and subsequently genotyped individuals from pools with allele frequencies different than expected. Allele frequencies based on individuals showed discrepancies from those based on pools, partially due to the duplicated nature of loci. One primer pair (koi89-90) was suggested to be quantitatively associated with red color.