吉富品系尼罗罗非鱼选育系F6～F9遗传变异的RAPD分析

利用随机扩增多态DNA（RAPD）技术对连续选育的吉富品系尼罗罗非鱼F6,F7、F8、F9R4个世代群体的遗传变异进行了分析。结果表明：（1）17条引物在4个世代的88尾个体间共检测到172个位点。（2）F6, F7,F8、F94世代的多态座位比例分别为：23．4％、21．1％、19．4％、18．3％，呈递减状态，U检验差别不显著（P〉0．05）；4世代的Nei遗传相似系数分别为：O．8961、0．9084,0．9186、0．9254，呈递增状态，t检验差别不显著（P〉0．05）；Shannon多样性指数分别为：0．1485、0．1314,0．1178、0．1083，呈递减状态，t检验差别不显著（P〉0．05）。（3）4世代间的遗传变异占群体总变异的比例是23．9％（Shannon多样性指数分析）和12．5％（AMOVA分析）。以上结果表明，4代选育虽未导致选育群体遗传多样性产生显著的差异，但却清楚地显示了逐代选育使选育系群体趋于纯化．选育系F8、F9世代已表现出较好的遗传稳定性。

RAPD analysis of genetic variation of GIFT strain Oreochromis niloticus from 6th to 9th generation

Random Amplified Polymorphic DNA (RAPD) was used to detect the variation of four successively selected generations( F_6,F_7,F_8,F_9 ) of GIFT strain of Nile tilapia(Oreochromis niloticus).The results showed that: (1)172 loci (300-2800 bp ) were examined by 17 random primers from 88 individuals of four generations. (2)The proportions of polymorphic loci of F_6,F_7,F_8,F_9 were 23.4%,21.1%,19.4%and 18.3% respectively,decreased generation by generation,but no significant differences among generations (U test, P>0.05);the Nei genetic identities of F_6,F_7,F_8,F_9 were 0.896 1,0.908 4,0.918 6,0.925 4 respectively ,increased generation by generation,but no significant differences among generations(t- test, P>0.05);Shannon genetic diversity indices of F_6,F_7,F_8,F_9 were 0.148 5,0.131 4,0.117 8,0.108 3, decreased generation by generation, but no significant differences among generations(t -test, P>0.05).(3)The contribution of the variation among four generations to the total variations of four generation was 23.1% in Shannon genetic diversity index and 12.5% in AMOVA analysis. The above results showed that, although a selection of four generations did not cause a significant difference of genetic diversities, it caused a clear trend in genetical purification, and the F_8 and F_9 generations have reached a rather high genetic stability as a genetic improved variety.