Mono- and polychromatic inner shell phenotype diversity in Pinctadamargaritifera donor pearl oysters and its relation with culturedpearl colour

International audienceThe pearl oyster Pinctada margaritifera has the specific ability to produce pearls with the widest range of coloursamong all pearl oyster species. This pearl colour diversity originates from the mantle biomineralising tissue(graft) of the donor oyster, which is originally responsible for the variety of colours of the inner shell surface.This study aimed to: 1) assess the geographic distribution and establish a first stocklist of the colourful oysterphenotypes used as donors in French Polynesia, and 2) investigate the phenotypic relation between inner shellcolouration and the corresponding colour of harvested pearls. With the support of a pearl farmers' network,we investigated the different donor phenotype frequencies among five collection sites (Ahe, Apataki, Takaroa,TakumeandMangareva). This donor evaluation was made during grafting of pearl oysters (N=49,938) obtainedfrom collector stations. Results showed that pearl production is mainly based on six common colourful donorphenotypes classified as monochromatic and polychromatic profiles, which shown different frequenciesamong the collection sites. Experimental grafts (N=4640)were then realised and subsequent culture conductedat a single site in order to avoid pearl colour variation due to environmental influences. Traceability between donors(N=232) and pearls (N=2776), revealed that: 1) yellow (gold) and aubergine (reddish) pearls could bemostly obtained by using the monochromatic yellowand red donor phenotypes, respectively, and 2) one third toone quarter of grey pearlswas inevitably harvested, whatever the polychromatic phenotype chosen as the donor,which leaves at least half the harvest composed of the attractive green and peacock colours. This preliminarystocklist of colour range together with analysis of the colour phenotype transmission between inner shell andpearl provide the basis for producing multiple pearl oyster “colour lines” through hatchery propagation andwould be helpful for future selective breeding programs.Statement of relevance: Donor shell colour selection predict colours of pearl