Abstract
To create asymmetric somatic hybrids, the genome of the so-called donor protoplast is fragmented prior to protoplast fusion. As a result, only a limited amount of the donor genome is transferred to the fusion product. This technique can circumvent some commonly observed problems related to symmetric fusion and offers a practical breeding tool for asexual hybridization. Genomes are typically fragmented by irradiation, microprotoplast production or application of metabolic inhibitors such as iodoacetamide. Irradiation and microprotoplast production fragment the nuclear genome, whereas iodoacetamide inactivates the cytoplasmic genome. It can therefore be used to introduce cytoplasmic male sterility, an important practical application. For hybrid verification and genome characterization, molecular markers and cytogenetic techniques are applied. This review highlights and discusses progress made during the last decade in spermatophytes asymmetric protoplast fusion.
Highlights
Plant cells from which the cell wall has been enzymatically or mechanically removed are called protoplasts
When comparing somatic hybridization to transgenic approaches, somatic hybridization enables broadening of the germplasm base, allows the transfer of uncloned multiple genes and generates products that are not subjected to the same legal regulations as transgenic lines [3,4]
In Bupleurum scorzonerifolium, asymmetric hybrids were obtained after protoplast fusion of UV treated B. scorzonerifolium and wheat protoplasts
Summary
Plant cells from which the cell wall has been enzymatically or mechanically removed are called protoplasts. When comparing somatic hybridization to transgenic approaches, somatic hybridization enables broadening of the germplasm base, allows the transfer of uncloned multiple genes and generates products that are not subjected to the same legal regulations as transgenic lines [3,4]. A somatic breeding protocol can typically be subdivided into the following steps: isolation, fragmentation (in case of asymmetric hybridization), fusion, regeneration and selection [10,11] (Figure 1). In symmetric fusion the complete genomes of both parent protoplasts are fused. Genome fragmentation of the donor parent encourages the elimination of much of its redundant genetic material in the somatic hybrid. Does asymmetric fusion introduce fewer genes in a recipient genome after fragmenting the donor genome, but elimination of disadvantageous genes or chromosomes proceeds quicker. Besides the progress made in spermatophytes asymmetric protoplast fusion related research during the last decade is highlighted and discussed
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