Growth traits and genetic parameters of hybrid families in Pinctada martensii

【Objective】To explore the growth and survival of two-way crossing hybrid of Pinctada martensii under different crossbreeding strategies，and to offer reference for the construction of cross breeding mating lines and selective breeding of P. martensii in Guangxi.【Method】36 hybrid families were esta blished in a complete diallel hybridization design which parents came from a F₄ generation Haixuan No.1 stock（H）and a F₁ local wild stock（Y）from Beihai. Control groups（PH and PY）were constructed from the F₁ generation of the H and Y parents. After 14 month’s mariculture， growth characters were compared among hybrid families（HY，YH）and purebred populations（PH，PY），genetic parameters of growth traits such as shell length（SL），shell height （SH），shell width（SW），and body weight（BW）were estimated by a mixed linear model（animal model）.【Result】Heritabilities（h²）of SL，SH，SW and BW of HY group were 0.241，0.149，0.220 and 0.062，respectively，while the range of genetic correlation（γ_g）and phenotypic correlation（γ_p） coefficient were 0.894-0.964 and 0.558-0.865. Heritabilities of SL，SH，SW and BW of YH group were 0.110，0.156， 0.121 and 0.067，respectively，while the range of genetic correlation and phenotypic correlation coefficient were 0.981- 0.989 and 0.603-0.881. The outcomes indicated that both two hybrid groups had medium-low heritabilities，and genetic correlation coefficients were higher than phenotypic correlation coefficients. The general combining ability（GCA）of Y （♀）and Y（♂）populations was high，indicating that Y（♀）and Y（♂）were more suitable for cross matching. The special combining ability（SCA）of SL，SH and SW of H（♂）×Y（♀）hybrids were high and had low-medium heritabilities. The growth heterosis（%）of four growth traits in the twohybrids ranged from -0.02% to 2.82% and -0.03% to 0.27%，respectively. SL had the highest heterosis，while SW had the lowest heterosis among all the groups. The proportion of families with heterosis in SL，SH and BW of H（♂）×Y（♀）hybrids ranged from 50.00% to 72.22%，and the selection rate of superior families was ≥50.00%. The proportion of over parent heterosis families in survival traits was 19.44%，while the proportion of heterosis families was 61.11%. Both the two hybrid groups and PY population showed advantageous survival rates. 【Conclusion】H（♂）×Y（♀）hybrids have advantage in growth，while Y（♂）×H（♀）hybrids have advantage in survival rate， and the two hybrid combinations all showcomprehensive heterosis，which can be used in general cross breeding. The offspring of Beihai wild population which with relative high GCA，heritabilities of SL and SH and high genetic correlation with BW，can be considered as specialized parental sources in the cross breeding of Guangxi P. martensii population. SL and SH should be given priority in the trait selection of 2-year-old parent individuals.