Mapping genes affecting shell color and shape in the Pacific OysterCrassostrea gigas

摘要

Variation in the color and shape of oyster shells is widely believed to be environmentally determined. However, Brake et al (2004 Aquaculture 229:89) recently provided evidence that shell and mantle edge color in the Pacific oyster, Crassostrea gigas, are heritable. We observed variation in shells of an F sub(2) family of Pacific oysters that appeared to be inherited, and we tested this hypothesis by statistical analyses and genetic mapping. Measures of shell shape, size and color were made from digital photographs of 179 oysters, using ImageJ software. Principal component analyses were used to consolidate the measured traits, and mapping was done on both principal components and some of the original individual traits. Mapping was made possible by a previously compiled linkage map for this same family of oysters, comprising 59 microsatellite DNA markers on 11 linkage groups. Using an interval mapping method, we identified a quantitative trait loci (QTL) for pigment saturation of the left valve on linkage group VIII, between ucdCgi183 and ucdCgi184: genotypes at ucdCgi183 explain 32% of shell color variance. Similarly, we identified two QTL for a pronounced left bend in some anteriorly viewed valves ("hook hinge") on linkage group III, in the adjacent intervals of cmrCgi-ucdCgil98-imbCgi49; genotypes at ucdCgil98 explain 32% of hook hinge variance. Left hook hinge appears to be recessive, while shell pigmentation is nearly additive. These observations suggest that genes, as well as environment play, a role in determining the color and shape of oyster shells. Markers associated with these QTL could be used to breed oysters with more desirable shell characteristics.