| Hyriopsis cumingii is a characteristic freshwater pearl mussel in China and a freshwater shellfish with the best pearl culture quality. When freshwater pearl yield increased, freshwater pearl quality did not improve at the same time. Selectively bred with excellent performance of the pearl production of H. cumingii is an important measure for realizing the freshwater pearl mussel breeding of sustainable development.In this paper, two different shell nacre color of H. cumingii were used for diallel cross, and then a comparative analysis was made to the shell nacre color of the hybrid offspring, and the correlative analysis was made between the pearl color and shell nacre color of H. cumingii, in order to provide references and theoretical basis for the selective breeding with pearl color as the goal character. Mainly included the following contents:This present study was carried out on the relationships between morphological traits and pearl production of two different shell nacre colors of H. cumingii. The results indicated that morphological traits and pearl production differed significantly between mussels with white and purple shell nacre,in which shell length, body weight, pearl diameter difference percent and round pearl percent were significantly different (P <0.01), shell height, shell width, pearl yield and pearl diameter were significantly different (P <0.05). The mean value of morphological traits and pearl production of mussels with purple shell nacre were higher than mussels with white shell nacre. The correlation coefficient between pearl yield and growth traits was as follows: shell width>body weight>shell length>shell height; The correlation coefficient between pearl diameter difference and growth traits was as follows: body weight>shell width>shell height; The correlation coefficient between pearl diameter percent and growth traits was as follows: shell width>body weight; The correlation coefficient between round pearl percent and growth traits was as follows: shell width> shell weight> weight. The proportions of white pearls produced by mussels with white shell nacre were higher than mussels with purple shell nacre, the proportions of red and purple pearls produced by mussels with purple shell nacre were higher than mussels with white shell nacre, it indicated that pearl color was affected by the shell nacre color. This present study showed that, besides the body weight and shell width, the shell nacre color could be a important breeding index in the genetic improvement of H. cumingii.Mussels with white and purple shell nacre were selected for diallel cross, and then made a comparative analysis to the shell nacre color of the hybrid offspring. The results indicated that, the shell nacre color of♂W×♀W and♂P×♀P offspring were identical to their parents, and a certain number of the shell nacre color of♂P×♀W and♂W×♀P offspring were the transition color between white and purple. The present study showed that the shell nacre color of H. cumingii could stably inherit.In this present study, the effect of shell nacre color on the color of pearls produced was examined. Saibos from donor mussels with white or purple nacre shells were grafted into the mantles of hosts that had either white or purple nacre shell color. After 12 months of culture, the colors of the pearls produced were measured visually and with the use of a surface colorimeter. White host mussels grafted with white saibos produced 61.23% and 0.91% white and purple pearls, respectively. White host mussels grafted with purple saibos produced 10.66% and 37.92% white and purple pearls, respectively. The proportions of white or purple pearls produced by the white host mussels differed significantly between mussels grafted with white or purple saibos (P<0.01). The proportions of white or purple pearls produced by the purple host mussels also differed significantly between mussels grafted with white or purple saibos (P<0.01). When white saibos were grafted into either white or purple host mussels, the proportion of white pearls produced was significantly different (P<0.05). A similar finding was shown when purple saibos were grafted into either white or purple hosts (P<0.05). Two-way analysis of variance indicated that the shell nacre color of donor mussels significantly influenced the color of the pearls produced (P<0.01). Moreover, the shell nacre color of host mussel also significantly influenced pearl color (P<0.05). The present study shows for the first time that the color of pearls produced by H. cumingii is not only affected by the shell nacre color of donor mussel but is also affected by the shell nacre color of the host mussel. |
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