Abstract
The Peruvian scallop (Argopecten purpuratus) has been introduced to China and has successfully been hybridized with the bay scallop (A. irradians irradians). The F1 hybrids of these two scallops exhibited a large increase in production traits and some other interesting new characteristics. To understand the genetic basis of this heterosis, nuclear gene and partial mtDNA sequences, and genomic in situ hybridization (GISH) were employed to analyze the genomic organization of the hybrids. Amplification of the ribosomal DNA internal transcribed spacer (ITS) showed that the parental ITS sequences were present in all the hybrid individuals, illustrating that the hybrid offspring inherited nuclear DNA from both parents. Sequence analyses of the ITS region further confirmed that the hybrids harbored alleles from their parents; some recombinant variants were also detected, which revealed some alterations in the nuclear genetic material of the hybrids. The analysis of mitochondrial 16S rDNA showed that the hybrids possessed sequences that were identical to the 16S rDNA of the female parents, proving a matrilineal inheritance of mitochondrial genes in scallops. In addition, GISH clearly discriminated between the parental chromosomes and indicated a combination of haploid genomes of duplex parents in the hybrids. The genetic analyses in our study illustrated that the F1 hybrids inherited nuclear material from both parents and cytoplasmic genetic material maternally, and some variations occurred in the genome, which might contribute to a further understanding of crossbreeding and heterosis in scallop species.
Highlights
Distant hybridization is a useful way of producing heterosis and an effective method of expanding the source of species variation and breeding new varieties
Yang et al [13] reported that adult hybrids were obtained from interspecific crosses of C. farreri 6 P. yessoensis, the investigation of the genetic composition of the adult hybrids indicated that no true hybrid could be confirmed [9]
The feasibility of crossbreeding has been tested among many commercial scallop species, such as C. farreri, A. i. irradians, P. yessoensis and M. nobilis, and the genomic organization and variation of the hybrids have been described [7,8,9,10,11,12]
Summary
Distant hybridization is a useful way of producing heterosis and an effective method of expanding the source of species variation and breeding new varieties. Interspecific crosses between divergent species have been widely performed in aquaculture to induce hybrid vigor [1,2], and some studies have shown that distant hybrids can present a wide range of genetic variation, including the hybrids of Clarias macrocephalus 6 Pangasius sutchi [3], Ctenopharyngodon idella 6 Cyprinus carpio [4,5] and Paralichthys olivaceus 6 P. dentatus [6]. Such variation has provided the conditions for genetic improvement in the aquaculture industry. Yang et al [13] reported that adult hybrids were obtained from interspecific crosses of C. farreri 6 P. yessoensis, the investigation of the genetic composition of the adult hybrids indicated that no true hybrid could be confirmed [9]
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