Indirect improvement of pearl grade and shape in farmed Pinctada margaritifera by donor "oyster" selection for green pearls

Type Article
Date 2014-08
Language English
Author(s) Ky Chin-Long1, Blay Carole1, Sham-Koua Manaarii1, Lo Cedrik2, Cabral Philippe3
Affiliation(s) 1 : IFREMER, UMR 241, EIO, Labex Corail,Ctr Pacifique, Tahiti 98719, Polynesie Franc, Fr Polynesia.
2 : Direct Ressources Marines & Minieres, Tahiti 98713, Polynesie Franc, Fr Polynesia.
3 : Gauguins Pearl Farm, Archipel Des Tuamotu, Polynesie Franc, Fr Polynesia.
Source Aquaculture (0044-8486) (Elsevier Science Bv), 2014-08 , Vol. 432 , P. 154-162
DOI 10.1016/j.aquaculture.2014.05.002
WOS© Times Cited 28
Keyword(s) Pinctada margaritifera, Cultured pearl quality, Pearl grade, Pearl colour, Pearl shape, Selective breeding
Abstract The top aquaculture species in French Polynesia is Pinctada margaritifera, a mollusc grown for the production of a unique gem: the black pearl. One of the challenges facing the pearl farming industry is to "produce less but better pearls" through genetic improvement. An experimental hatchery system was used to generate full-sib families to be tested for their potential as donor "oysters". A large-scale grafting experiments was done and seven cultured pearl quality traits: grade, surface defects, lustre, darkness level, visual colour categories, circles and shape categories were recorded. Our results revealed, for the first time, significant phenotypic relationships between these quality traits. The grade A cultured pearl class had the largest proportion of pearls with a green overtone (65%), the lowest number of circled pearls (15%) and the maximum of round-shaped pearls (45%). In contrast, the "reject" cultured pearl class had the largest proportion of pearls with grey bodycolor (65%), the greatest number of circled pearls (35%) and the maximum with a baroque shape (nearly 60%). When grade components were studied separately, cultured pearls in the zero surface defect class exhibited the same tendencies as grade A pearls, contrasting with the class where there were more than ten defects on the surface of each pearl. When cultured pearls were classified according to the presence or absence of lustre, pearls with lustre mostly had a green overtone colour, while pearls without lustre did not. These findings have major implications for cultured pearl quality improvement, as modern genetic breeding methods can increase the proportion of high quality cultured pearls though selected lines of donor oysters capable of producing pearls with a green overtone. Selection of appropriate donor phenotypes, incorporation of pigmentation traits into a pearl oyster breeding program and production of lines with desirable colours will be developed for oyster aquaculture in French Polynesia.
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