Shell color is a heritable phenotypic marker that has been increasingly used in bivalve breeding. However, its breeding potential in Ruditapes variegatus remains unclear. In this study, we established a 3 × 3 diallel cross based on inner shell color using three inner shell color phenotypes, including red (R), white (W), and orange (O). Heterosis, thermal tolerance, and genetic parameters were evaluated. Among all combinations, RW (R♀ × W♂) showed the best overall performance. RW exhibited positive heterosis for survival from day 4 onward and maintained strong heterosis for growth before overwintering. Mid-parent heterosis (MPH) ranged from 3.56% to 32.42%, while high-parent heterosis (HPH) ranged from 0.72% to 32.42%. Under heat stress, RW showed the highest survival rate (64.86%). Hazard ratio analysis identified 12 heat-tolerant families (HR 1), most of which belonged to the RW combination. Cluster analysis further showed that family R2W1 had the best comprehensive performance. Heritability of heat tolerance was low (0.11–0.17), suggesting that family selection is more suitable for this trait. Before day 30, heritability of growth traits ranged from 0.06 to 0.34. At day 60, heritability increased to 0.56–0.69. Based on these results, family selection is recommended at early stages, followed by individual selection after day 60. This study demonstrates that inner shell color can serve as an effective marker for crossbreeding in R. variegatus and provides a practical strategy for developing fast-growing and heat-tolerant strains.
Li et al. (Thu,) studied this question.