| Megalobrama amblycephala and Parabramis pekinensis are the favorite fish because of their characteristics of delicious meat and fast growth in China.Not only,M.amblycephala and P.pekinensis have no obstacle to cross between them,but also,the hybrids of reciprocal cross have some advantages in growth and stress resistance and they are belongs to Megalobrama and Parabramis respectively.Therefore,we conducted reciprocal cross tests(M.amblycephala ♂ × P.pekinensis♂ for orthogonal,P.pekinensis♀×M.amblycephala♂ for anti-crossover)and compared the embryonic development,hybrid growth of the reciprocal cross.Molecular maker of the hybrids were developed also.The main research results were as follows:1.A comparative study of reciprocal cross F1 embryonic development between M.amblycephala and P.pekinensis.Artificial propagation tests on reciprocal cross F1 between M.amblycephala and P.pekinensis.We observed the embryonic development of reciprocal cross at a water temperature of 21±1℃.The results suggest the M.amblycephala mature eggs were found to be about glutinous,light green in color,and(1.19±0.09)mm in diameter,(1.38±0.11)mm after fertilization and inflation.The P.pekinensis mature eggs were observed drifting,light cyan,and(1.30±0.08)mm in diameter,(4.05±0.20)mm after fertilization and inflation.When the water temperature was 21℃,the hatching time was 33.42h and 26.17h of the reciprocal cross,development accumulated temperature was 705.93(℃·h)and 554.30(℃·h),respectively.According to the characteristics of embryonic development,the reciprocal cross F1 development had divided into 30 periods of 7 stages.2.A comparative study of the growth of the F1 generation of reciprocal cross between M.amblycephala and P.pekinensis.The body weight and length data of the reciprocal cross F1 offspring had collected every 30 days in the 180 days growth test.The weight and body length of the anti-cross offspring are higher than those of the orthogonal offspring 21.10%and 9.26%,respectively.Anti-cross offspring grow faster than orthogonal offspring.Orthogonal offspring is y=0.0142X3.1204(R2=0.9854)and anti-cross offspring is y=0.0139X3.1324(R2=0.9903)by fitting the growth curve of both body lengths and body weights.The curve fits well,and they all show positive allometric growth.There are significant differences in categorical weight gain rate,absolute growth rate,accumulation volume,and coefficient of fatness for reciprocal cross offspring.The maximum absolute weight gain rate was 0.1121 and 0.1514 of reciprocal cross offspring at 150d,respectively.The maximum absolute growth rates are 0.1069 and 0.1040 of reciprocal cross offspring at 150d,respectively.The maximum accumulation volume of orthogonal offspring is 0.0037 at 60d,and the anti-cross offspring is 0.0067 at 150d.The Coefficient of the fatness of orthogonal offspring is 1.9585 at 180d,and the anti-cross offspring is 1.8435 at 120d.In summary,anti-cross offspring grow faster than orthogonal offspring.3.Molecular marker study of F1 mtDNA of reciprocal cross between M.amblycephala and P.pekinensis.The shape is extremely similar and difficult to distinguish for reciprocal cross F1 between M amblycephala and P.pekinensis.The 85.16%similarity of mtDNA sequences between M amblycephala and P.pekinensis.MtDNA follows the characteristics of maternal inheritance,using the mtDNA sequences of M.amblycephala and P.pekinensis for primer design and sequencing comparison of PCR products.The results showed that the mtDNA of the reciprocal cross offspring had more SNP loci and a higher density on the genome.One of the SNP sites accounted for 93.33%of the conversion and 6.67%of the inverted SNP sites.After verification,the verification rate of these SNP sites reaches more than 90%,which can effectively distinguish for reciprocal cross F1 Offspring. |
