| Chlamys farreri ,which belongs to Mollusca, Bivalvia, Pterioidae Pectinidae, are widely distributed on the China from Donghai Sea to Bohai Sea, Korea and Japan. This species has been the main aquacultrue shellfish for many years in northChina. In recent years , however , they have suffered heavy decrease in the resource , and the wild stock and genetic diversity have been threatened to some extent due to overfishing and changes of ecological environment . Investigating genetic variation and studying the genetic difference are beneficial to the resource restoring , protection and genetic improvement . For this sale , Japanese scallops(JP) were introducted and hybridization program was carried out between the native population and the introducted population。Polyacrytamide gel electrophoresis(PAGE) was used to determine the genetic variation of two natural populations of Chlamys farreri(Jones & Preston) ,one was collected from Dalian ,China, the other was from Japan, at the same time , isozymes of the self-bred progeny and their reciprocal hybrids were studied.6 isozymes were analyzed in the two parental populations, including their locus number,structure,alleles etc, altogether 18 gene loci and 28 alleles were recorded . The statistical results show that the genetic diversity of Japan population(JP) is higher than China population(CP), with 45.45% of the proportion of polymorphic locus (P.99), 0.1531 of the mean observed heterozygosity(Ho), and 0.2331 of the mean respected heterozygosity(He). In CP, these values are 41.18%, 0.1295 and 0.1695 accordingly. 9 isozymes were studied, and 13 loci were detected in every F1 generation population. The results show that the genetic diversity of filial generations is higher than self-bred progeny's,the hybrid vigor has manifested at metabolization level 。The proportion of polymorphic loci (P.99) in F1 generations was 30.77-36.36%, the mean observed heterozygosity (Ho) of JMCF(Japanese male×Chinese female)was the highest with 0.1727, the rest populations were: JFCM(Japanese female×Chinese male) 0.1536,CP 0.1273 and JP 0.1055,the mean effective number of allels per locus in F1 generations :CP's was the highest with 1.7318 ,JP's was the lowest with 1.6718, the filial generations'values were in the midle of the CP's and JP's and between them there was no brightly difference, with 1.6955(JFP) and 1.6927(JMP). Heterozygote deficiency commonly existed in all four populations, with mean heterozygote deficiency index -0.1125(JMP),-0.1877(JFP),-0.3174(CP),-0.4093(JP). With respect to genetic similarity , genetic distance and cluster analysis among samples of F1 generation , it showed that the most genetic identity is between JFP and JMP, ( I = 0.9934 , Dnei = 0.0066 ) , the next was between JP and JMP (I = 0.9873 , Dnei = 0.0128 ) , the third was JP and JFP , with I = 0.9681 , Dnei = 0.0325 ; the fourth was JP and CP , with I = 0.9035 , Dnei = 0.1015 ; the fifth was CP and JMP , with I = 0.8862 , Dnei = 0.1208 , and the furthest was between CP and JFP, with I = 0.8648 , Dnei = 0.1452 . From the results , it was evident that the relations between filial generations and JP is closer than that between filial generations and CP. In general, the hybridizition technique between subspecies for improvement of quantitative and qualitative traits is practicable. |
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