Heritability estimation of high salt tolerance in razor clam (Sinonovacula constricta)

As an important marine mollusk, the growth and development of razor clams (Sinonovacula constricta) are affected by salinity. Genetic selection for salt tolerance is an imperative and effective approach to the improvement of growth and production. To examine whether the tolerance to high salt can be included in razor clam breeding programs, we conducted a genetic analysis of high salt tolerance using three phenotypes and four statistical models. The correlation between tolerance and growth traits was evaluated simultaneously. In this study, we used 9-day experimental stress data of 1005 individuals from 17 full-sib families (the offspring of 17 sires and 17 dams). The survival rate of the families ranged from 0% to 100%, suggesting that the viability of razor clams was different under diverse high salt stress. A positive Pearson and Spearman correlation existed between high salt tolerance and growth traits. A very high genetic correlation (0.886-0.999) was also observed between them, indicating indirect breeding was feasible. Heritabilities of tolerance to high salt were from low to high, with values of 0.55-0.64, 0.11, and 0.047-0.487 for trait TS (test survival), trait DD (day of death), and trait TDS (test-day survival), respectively. The Pearson correlation coefficients of families estimated breeding values between different models ranged from 0.921 to 0.998 which indicated a near-identical ranking of families. This study demonstrated that the salt tolerance of razor clams could be improved genetically through selective breeding. Overall, cross-sectional threshold and linear repeatability models were the most appropriate in estimating heritability for salt tolerance with trait TS and trait TDS in this species. Our study provides important information to guide the effective selection for salt tolerance in S. constricta.