Estimation of non-nucleated pearl quality traits from donor and host mussel-derived genetic parameters in the golden strain of Hyriopsis cumingii

Abstract

Hyriopsis cumingii is the most important freshwater mussel for pearl production in China and its pearl color is polymorphic. In order to establish a selective breeding program, the genetic parameters of growth and inner shell color traits of golden H. cumingii were evaluated in our lab. Due to the long culture time for pearl production, very little is known about the genetic parameters of commercially important pearl traits. In this study, the genetic parameters of donor-derived and host-derived pearl quality traits were estimated and the genetic contribution from donor and host interaction to pearl quality traits was analyzed. In addition, the correlation of pearl traits with growth traits, inner shell color and luster of donor and host mussels was examined. Microsatellite-based DNA parentage analyses were used to assign mussels to families and populations of origin. A total of 653 individual mussels could be clearly assigned to eight paternal half-sib and 39 full-sib families. Five pearl traits that constitute the major determinants of pearl value (color, luster, size, weight and roundness) were recorded at harvest. Pearl weight and size were significantly correlated with growth traits of the host mussel, while pearl color and luster were significantly correlated with the inner shell color and luster of the donor mussel. Our results indicated that the b⁎ value may be a representative parameter for the evaluation of pearl color in the golden strain in Hyriopsis cumingii. Donor-derived heritability estimates for pearl luster (h2 = 0.37) and color b⁎ values (h2 = 0.47) were high, while heritability estimates for pearl weight (h2 = 0.16), size (h2 = 0.18) and roundness (h2 = 0.07) were low to moderate. By contrast, host-derived heritability estimates for pearl luster and color were low to moderate, while heritability estimates for pearl weight (h2= 0.28), size (h2= 0.24) and roundness (h2 = 0.16) were moderate. The genetic contribution of the donor and host (D × H) interaction on pearl color and pearl luster were low, while the genetic contribution of the D × H interaction on pearl size, weight and roundness were moderate to high. This study revealed the possibility of promoting different selective breeding programs for improving host and donor mussels. Selecting mussels with excellent luster, golden color and higher growth traits as the donors and mussels with excellent growth traits as the hosts may cultivate bigger and brighter golden pearls.