Traditionally, sexual hybridization has been used to obtain hybrid plants, but the technique has limitations, such as the ability to fuse only closely related species and the presence of disaffinity barriers. These limitations can be overcome by somatic cell hybridization. Plant somatic cell hybridization by protoplast fusion is a plant breeding technique. If the complete genomes of two different species are quasi-combined, a twofold somatic cell hybrid is produced. This is most common in somatic cell hybridization experiments. Somatic cell hybridization offers the possibility of obtaining sexually incompatible germplasm resources between crop species and distant relatives, merging the genomes of sexually dysfunctional cultivars or breeding lines, and replacing one cytoplasm with another with little effect on the nuclear genome. Using more than 20 species of Solanum, hundreds of inter/intraspecific somatic hybrids have been developed by protoplast fusion with a wide range of traits such as agronomic and biotic/abiotic stresses. With the increasingly successful recovery of fusion products, somatic hybrids have been used in crop genetics and breeding and, more recently, in genomics studies.

Fig. 1. Generation of somatic hybridization introgression lines. (Liu et al., 2015)

Our solution for pre-breeding genomics in somatic hybridization

Somatic hybridization relies on tetraploid embryogenesis following the fusion of protoplasts isolated from embryogenic healing tissue lines with chloroplast protoplasts from complementary parents, followed by a validation process. CD Genomics offers several types of polymerase chain reaction (PCR)-based molecular markers to validate crop somatic hybridization and/or their ploidy levels, such as random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), cleavage amplified polymorphic sequences (CAPS), and simple sequence repeats (SSR).

We typically use expressed sequence tags (EST)-SSR to help you determine ploidy levels and confirm somatic hybridization. We extend this application directly to the rapid validation of somatic hybrids generated by simply adding two genomes. Co-dominant EST-SSR markers in diploid individuals have either two identical pure alleles or two different heterozygous alleles, depending on the number of alleles and amplified DNA fragments.

The process of somatic hybridization induces a wide range of genetic and epigenetic changes, including sequence deletions, alterations in the regulation of gene expression, changes in cytosine methylation patterns, and activation of quiescent retrotransposons. Our NGS and long-read sequencing technologies can characterize these changes. We also provide sequencing of the progeny of some hybrid combinations to analyze intergenomic translocations.

Our genotyping by sequencing (GBS) service allows for extensive characterization of both nuclear and cytoplasmic genomes, analyzing local chromosomal instability in all nuclear somatic hybridization as well as whole chromosome elimination in two hybrids.

Applications of somatic hybridization

• Disease-resistance: with the help of somatic hybridization, disease-resistance genes from one plant have been transferred to many other plants.
• Environmental tolerance: plants have been hybridized to tolerate extreme environments such as cold, heat, and salt.
• Quality traits: many plants have desirable traits such as high protein content.
• Cytoplasmic male sterility: many traits in cells are controlled by the cytoplasm. The advantages of somatic hybridization is the introduction of such traits in hybrids, e.g. resistance to antibiotics, herbicides, and male sterility.

Advantages of somatic hybridization

• Somatic hybridization can be carried out in young plants.
• Study cytoplasmic genes and their functions becomes easy.
• Protoplast fusion provides unique nuclear-cytoplasmic combination in hybridized cells.
• It produces innovative plants with desirable characteristics.
• SSR markers can be used to confirm somatic hybridization as long as polymorphisms exist between the two donor parents.

CD Genomics offers comprehensive solutions for pre-breeding genomics of somatic hybridization. We use gene sequence technology for genotyping EST-SSR markers to help in the definitive identification and confirmation of tetraploid somatic hybridization. Ploidy level and allelic complementarity were simultaneously determined by appropriate selection of EST-SSR marker loci in parental lines. If you are interested, please feel free to contact us.

Reference

1. Liu, Shuwei, et al. "Genetic and epigenetic changes in somatic hybrid introgression lines between wheat and tall wheatgrass." Genetics. 199.4 (2015): 1035-1045.

Related Services
Animal and Plant Custom PCR Services
Microsatellite (SSR) Analysis Services
Animal and Plant Whole Genome Sequencing
Agricultural NGS Services
Long-read Sequencing
Genotyping By Sequencing (GBS)