Artificial interspecific backcrosses between the hybrid of female Crassostrea hongkongensis x male C-gigas and the two parental species

摘要

To explore the possibility of performance improvement in the hybrids of Crassostrea hongkongensis female x Crassostrea gigas male, backcross progeny and F-2 hybrids were produced and evaluated. Three sets of replicates were successfully generated; each consisted of single crosses (HH, GG and HG), two female backcrosses between female hybrids and two male pure species (Hg/H and Hg/G), two male backcrosses between male hybrids and two female parents (H/Hg and G/Hg) and F-2 hybrids (Hg/Hg). Fertilization, survival, growth and gonad development of these experimental groups were evaluated. All backcross groups exhibited high fertilization levels; however, the female backcrosses (Hg/H and Hg/G) and F-2 hybrids exhibited a low hatching rate. Survival and growth superiority of the backcross progeny was observed from the larval stage to the adult stage, although outbreeding depression of the F-2 hybrids occurred. Interestingly, all backcross progeny and F2 hybrids were fertile with functional gametes and normal sex ratios when fully matured. The genetic recombination of the backcross progeny and Mendel's genetic segregation of the F-2 hybrids were detected with the nuclear gene marker in the backcross. Our results revealed that artificial interspecific backcrosses are successful, and the backcross progeny are viable, fertile, and fast-growing, and therefore hold promise for potential utilization in aquaculture as a new oyster stock resource.