缢蛏选育系F_5的生长优势比较及育种效应分析

Growth comparison and selective breeding of a fifth-generation selected line of Sinonovacula constricta

以6个缢蛏(Sinonovacula constricta)自然群体(浙江象山群体、浙江乐清群体、福建霞浦群体、福建长乐群体、江苏射阳群体和上海崇明群体)为材料,构建基础群体F_0,采用群体选育方法进行多代连续选育(选择强度2.063),比较了选育系F_5与对照群体的生长差异,并估计F_5的选择反应、现实遗传力和遗传获得。结果表明,F_5的卵径及受精率与对照组无显著差异(P>0.05),但F_5的变态率、存活率及后期壳长生长明显优于对照组(P<0.05);7~360日龄F_5壳长的选择反应、现实遗传力与遗传获得的变化范围分别为0.30~0.78,0.14~0.37和4.83%~42.18%,平均为(0.49±0.06),(0.23±0.08)和(26.49±11.73)%。研究结果表明,对缢蛏的连续多代选育是有效的,可以明显提高其存活能力和主要经济性状。

The razor clam Sinonovacula constricta is wildly distributed in China, Japan, and Korea. The razor clam has high nutritive and economic value and is one of four marine bivalves produced in China. Artificial breeding and frequent inbreeding have decreased the genetic diversity of razor clams, and the germplasm resources are degraded. As a result, massive razor clam mortalities occur occasionally. Cultured clams are generally small and have poor disease resistance, and no superior commercial razor clam varieties have been bred for the commercial market. Therefore, improving genetic traits and breeding outstanding varieties of razor clams via artificial selection are primary goals of razor clam culture. In this study, six natural populations of S. constricta （Zhejiang Xiangshang and Leqing populations, Fujian Xiapu and Changle populations, Jiangsu Sheyang and Shanghai Chongming populations） were selected as the F0 material structure foundation populations, and continuous multiple-generational breeding （selection intensity：2.063） was carried out using the mass selection method. The growth difference between the F5 breeding strain and a control population was compared. The selection response, realized heritability, and F5 heredity acquisition were evaluated. The results showed no differences in egg diameter or fertilization rate between the F5 generation （P〉0.05） and the control group. However, the metamorphosis rate, survival rate, and late growth in shell length of the F5 generation were significantly superior to those of the control group （P〈0.05）. Variations in the selection response of shell length, realized heritability, and heredity acquisition of F5 during days 7-360 were 0.30-0.78, 0.14-0.37, and 4.83%-42.18%, respectively, and the means were （0.49±0.06）, （0.23±0.08）, and （26.49±11.73）%, respectively. These results suggest that continuous multiple-generational breeding of razor clams was effective, as it significantly improved survivability and the major economically important traits. Continuous selection of five generations of razor clams was effective, making further breeding to identify new razor clam varieties with desirable traits possible. The genetic gain in shell length was generally low, probably because of genetics and environmental factors. Razor clams are a mudflat bivalve that hide in silt, and their long body reduces adaptability to the environment. Hence, breeding should focus on weight selection to obtain more practical results.