The phenotypic predisposition of the parent in F1 hybrid is correlated with transcriptome preference of the positive general combining ability parent

Background: Sprague and Tatum (1942) introduced the concepts of general combining ability (GCA) and specific combining ability (SCA) to evaluate the breeding parents and F1 hybrid performance, respectively. Since then, the GCA was widely used in cross breeding for elite parent selection. However, the molecular basis of GCA remains to unknown. Results: We studied the transcriptomes of three varieties and three F1 hybrids using RNA-Sequencing. Transcriptome sequence analysis revealed that the transcriptome profiles of the F1s were similar to the positive GCA-effect parent. Moreover, the expression levels of most differentially expressed genes (DEGs) were equal to the parent with a positive GCA effect. Analysis of the gene expression patterns of gibberellic acid (GA) and flowering time pathways that determine plant height and flowering time in rice validated the preferential transcriptome expression of the parents with positive GCA effect. Furthermore, H3K36me3 modification bias in the Pseudo-Response Regulators (PRR) gene family was observed in the positive GCA effect parents and demonstrated that the phenotype and transcriptome bias in the positive GCA effect parents have been epigenetically regulated by either global modification or specific signaling pathways in rice. Conclusions: The results revealed that the transcriptome profiles and DEGs in the F1s were highly related to phenotype bias to the positive GCA-effect parent. The transcriptome bias toward high GCA parents in F1 hybrids attributed to H3K36me3 modification both on global modification level and specific signaling pathways. Our results indicated the transcriptome profile and epigenetic modification level bias to high GCA parents could be the molecular basis of GCA.