Abstract: To study the cold tolerance and growth performance ofO.mossambicus×O.niloticus hybrid lines,low-temperature stress test and growth comparison test were used to select the excellent pedigree of cold-tolerant Egyptian strainof Nile tilapia (female) and the America strains of Blue tilapia (male).Through the cold tolerance and growth performance evaluation and the low temperature breeding,breeding,parents Nile and Blue tilapia were obtained to crossbreeding.36 of F₁ generation O.mossambicus×O.niloticus hybrid families were mated through nested paired method (the proportion of male and female was 3∶1).The results showed that,the mean Semi-lethal temperature of 31 families of O.mossambicus×O.niloticus hybrid F₁ generation was 7.45 °C,and 8.81% lower thanin natural populations,the average relative survival rate and average growth speed increased by 17.6% and 13.2%,respectively.2 excellent F₁ generation of crossbreeding combination (F₁CT0401,F₁CT0203) were obtained,and the mean Semi-lethaltemperature were by 7.02 °C and 7.24 °C,low mortality rates were 40.5% and 49.5%,respectively,which decreased 17.4% and 11.35% than in natural populationsof O.mossambicus×O.niloticus hybrid,the relative mortality decreased by30% and 26.9%,yield increased by 12.9% and 38.7% respectively.The survival rate was(84.39±6.65)% of farming demonstrated F₁ generation cold tolerant O.mossambicus×O.niloticus hybrid,and the average produce was (1 220.20±94.77) (kg·667 m^-2),the average size was (723.0±101.2) g.Compared with the control group,the overwintering mortality decreased by 19.11% (P＜0.05)and the average yield increased by 36.59% (P＜0.05).Thecold tolerance and growth properties of F₁ O.mossambicus×O.niloticus hybrid had been greatly improved than the natural populations.

Key words: O.mossambicus×O.niloticus, crossbreeding system, cold tolerance, growth performance, selection and breeding