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

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.