Asymmetric protoplast fusion in Chrysanthemum

General introduction

When crossing plants, not only genes of interest are transmitted into the seedling but also undesired DNA. Using cell fusion, is it possible to achieve somatic hybrids that contain only a certain fraction of the genetic material of one of both contributing species? How should we fragment the genetic material of this 'donor' parent?  Can we fuse those fragments with the complete 'acceptor' parent? And how should we regenerate the fused cells into mature plants? The aim of this project is to evaluate and integrate the different steps in the development of these so-called 'asymmetric somatic hybrids'. Chrysanthemum, one of the economically most important ornamental crops worldwide, is used as a model crop.

Research approach

We first optimize protoplast (cells without cell wall) isolation. For fusion, we use a chemical approach (polyethylen glycol mediated) and an electrical approach (electroporation). Then we evaluate which approach is most efficient. Possible treatments to induce fragmentation are UV irradiation and microprotoplast isolation. Once again we determine which technique is best. We pay the most attention to the in vitro regeneration of complete plants from protoplasts, which we expect to be the biggest stumbling block in our research. Another aim is to create a protocol for the regeneration of the 'acceptor' parent, as we expect them to be closely genetically related to fusion products. To do so, we test several parameters such as genotype, explant type, protoplast density, phytohormones and fusion treatments.

 

Relevance/Valorisation

The ultimate goal of this research project is to develop new technology for asymmetric somatic fusion. This type of hybridization is innovative. Such an advance would greatly reduce the time required to create a new hybrid compared to traditional breeding programmes. Breeders currently need to rely on a number of backcrosses to reduce the number of undesired genes resulting from hybrid crossing products. In our technique, the fragmentation that precedes the cell fusion largely eliminates the donor genome. This project also expands the field of knowledge on fragmentation, fusion, regeneration and selection. That knowledge can be applied to diverse breeding programmes. As for Chrysanthemum itself, this technique has potential to be a significant innovation compared to traditional crosses or breeding through irradiation. It will enable breeders to exploit genes from 'wild' sources and diversify the commercial assortment.