新吉富罗非鱼选育过程中遗传变异的AFLP分析

AFLP analysis of genetic diversity of GIFT strain Oreochromis niloticusduring selection processing by AFLP

为了查明罗非鱼选育过程中发生的遗传变异,采用扩增片段长度多态（AFLP）方法,对吉富品系尼罗罗非鱼选育系基础群体F0、选育群体F6-9进行遗传差异分析.8对EcoR I/Mse I引物组合共产生308条清晰的DNA带.多态位点比例在群体间呈现出差异性,F0代为51.3%,F6代为48.7%,F7代为47.1%,F8代为46.1%,F9代为43.8%.平均基因多样性指数F0代为0.1834,F6代为0.176 5,F7代为0.1754,F8代为0.1620,F9代为0.1560.Shannon多样性指数F0代为0.2684,F6代为0.2626,F7代为0.2614,F8代为0.2415,F9代为0.2319.各项遗传多态性指标一致表明,F0代群体遗传多态性水平最高,随选育世代数的累进,选育群体的遗传多态性水平呈现出下降的趋势.吉富品系罗非鱼选育群体间遗传相似性水平（Nei,1972）较高,为0.9675~0.9875,群体间遗传距离较小,大小范围为0.0126~0.0331.经过偏差校正,Nei（1978）计算得到选育群体间遗传相似性大小为0.9726~0.9926,群体间遗传距离为0.0074~0.0278.随选育世代数的累进,选育群体与基础群体间的Nei（1972,1978）遗传相似性呈减弱趋势,而Nei（1972,1978）遗传距离逐渐呈现出增大趋势.引物组合E-AAG/M-CTA产生一条大小为502 bp的特异性DNA条带,该条带在不同选育世代间随世代数的累进呈现出频率增高的趋势.

Amplified fragment length polymorphism（AFLP） was used to detect the genetic variation of the base population F0,and selected generations,F6-F9 of GIFT strain Nile tilapia.Eight Eco R I and Mse I primer combinations produced 308 bands totally.The ratio of polymorphic bands varied between these five populations,F0：51.3%,F6：48.7%,F7：47.1%,F8：46.1%,F9：43.8%,respectively.The average gene diversity index was 0.183 4,0.176 5,0.175 4,0.162 0,0.156 0,respectively.Shannon genetic diversity index was 0.268 4,0.262 6,0.261 4,0.241 5,0.231 9,respectively.These results showed that F0 was with the greatest genetic diversity,and it decreased following selection processing.Nei＇s（1972） genetic identity between populations was 0.967 5~0.987 5,which was relatively high,and genetic distance was in the range of 0.012 6~0.033 1,which was relatively small.Nei＇s（1978） genetic identity between populations was 0.972 6~0.992 6,and genetic distance was 0.007 4~0.027 8.Following selection processing,the genetic identity（Nei,1972,1978） between F0 and selected populations decreased,but the genetic distance between F0 and selected populations increased generation by generation.The E-AAG/M-CTA primer combination amplified one DNA band of 502 bp,which was presented more and more frequent in the selected generations F6-F9.