Molecular insights into heterosis for Vibrio alginolyticus resistance in crosses between two geographically distinct wild populations of Ruditapes philippinarum

Intraspecific crossbreeding is one of the effective methods to improve the disease resistance of R. philippinarum , and excellent traits can usually be produced in the hybrid progeny. In this study, we conducted a challenge experiment with V. alginolyticus on the hybrid progeny (D♀ × W♂ (DW) and W♀ × D♂ (WD)) and inbred progeny (D♀ × D♂ (DD) and W♀ × W♂ (WW)) of R. philippinarum Dalian Jinshitan (Liaoning Province) and Weihai moyedao (Shandong Province) populations, and found that the hybrid progeny had heterosis in resistance to V. alginolyticus . To explore the molecular mechanism of this heterosis, we then performed transcriptome sequencing on the hybrid and inbred progeny challenged with V. alginolyticus for 48 h and those that were not stressed. The results showed that 548 and 260 differentially expressed genes were detected in the hybrid progeny DW and WD, respectively, and 399 and 520 differentially expressed genes were detected in the inbred progeny DD and WW, respectively. Among them, the mRNA expression levels of immune genes and inflammatory factors such as Hsp70 , TNFSF13 , TRAF6 , IFI44 , IL17 in hybrid progeny were higher than those in inbred progeny, which may be one of the reasons for heterosis. Heterosis-related module (darkturquoise) was identified and the genes of this module were significantly enriched in the phagosome pathway. These results may provide a molecular basis for the superior ability of intraspecific hybrid progeny of R. philippinarum to survive attack by V. alginolyticus than their parents, thereby deepening our understanding of heterosis in R. philippinarum . • The hybrid progeny of R. philippinarum showed heterosis in resistance to Vibrio alginolyticus . • The expression of immune related genes in hybrid progeny were higher than in inbred progeny. • Modules and hub genes related to V. alginolyticus resistance were identified by WGCNA. • Key pathways and target genes related to Vibrio resistance in Manila clam were identified.