Keywords: 
• Litopenaeus vannamei /
• line /
• growth /
• resistance /
• resistance to WSSV /
• genetic characters

Abstract: White-leg shrimps（ Litopenaeus vannamei） bred by selection for eight years were cultured without discharge of sewage,change of water,air ventilation and cleaning of dead shrimps in outdoor cement pools A and B. The remaining shrimps cultured in the pools A and B for a year were used as parents,and forty- four lines of F₁ generation were bred from the pools A and B. Thirteen lines of the shrimps were selected to compare their growth,stress tolerance and resistance to WSSV to study the genetic characters of the stress-tolerant lines of L.vannamei. Each F₁ generation of the shrimps was found to have a significant difference in the growth（ P ＜ 0. 05）.The line F₁-08 in the pool A（ A F₁-08） had an average body weight of 28. 63 g,the highest in the pool A. At the salinity from 28‰ to 5‰ the line F₁-12 in the pool B（ B F₁-12） had a mortality or death rate of 23. 33%,the lowest in the pool B. The F₁ generation was significantly higher in mortality in the pool A than that in the pool B and the F₁ generation of crosses between the shrimps in the pools A and B（ P ＜0. 05）. The F₁ generation in the pool B and that of crosses between the A and B pools（ AB F₁） had a lower mortality than the control groups Gjk and Klw and a significant higher mortality than the control Sis（ P ＜0. 05）. At the concentration of ammonia nitrogen of 31. 67 mg·L^-1 each F₁ generation of the shrimps was significantly different in the mortality（ P ＜0. 05） and was significantly lower than the control group Sis（ P ＜0. 05）. The A F₁-09,A F₁-13,A F₁-19,A F₁-20,A F₁-13 and A F₁-08 had a mortality of 0%,the lowest. At the concentration of nitrite of 50. 51mg·L^-1 each F₁ generation of the shrimps was significantly different in mortality（ P ＜0. 05）,and lower than the control groups Gjk,Klw and Sis（ P ＜0. 05）. The A F₁-08,A F₁-10,A F₁-18,A F₁-19 and A F₁-20 were the lowest in mortality（ 0）. After infected with WSSV,the B F₁-13 had a mortality of 53. 30%,which was the lowest and significantly lower than the control group F₂（ P ＜0. 05）. The A F₁-08 had remarkably higher growth,the B F₁ and AB F₁ had a stronger ability for adaptation to the sudden change of salinity. All the F₁ generations had a higher adaptation to the sudden change of ammonia nitrogen concentration than the control Sis and to the sudden change of nitrite concentration than the controls Gjk,Klw and Sis. The BF₁-13 had a higher resistance to WSSV. The findings provide evidence for selective breeding of new tolerant lines of L. vannamei.