Main research question/goal
F1-hybrids have been bred from inbreeding lines. They have an estimated potential to increase inulin production in industrial cichory roots by 20%. (This is important because food companies use inulin, a chain of fructose molecules, as a prebiotic dietary fiber in dairy and bakery products, among others. Inulin stimulates the growth of beneficial intestinal bacteria. And the product is also used as fat replacer or even as an ingredient in the cosmetic sector.) This research project is directed towards two indispensable conditions for F1 hybrid creation: the quick production of homozygous parent plants and the stability of cytoplasmic male sterility (CMS). How can we induce homozygous parent plants? What techniques are most suitable and can we influence their efficiency? And what about CMS stability in cichory? Can this sterility be suspended - either temporarily or not - by environmental factors, such as high temperature?Research approach
We test two techniques to induce homozygous plants. First, we culture microspores. We try to regenerate these cells in vitro so that they contain only half of the chromosome number of regular cells (hence their name, 'haploid cells'). We evaluate the following parameters: developmental stage of the microspore, medium composition, and parental genotype. Our second technique is to perform interspecific hybridisations with related Asteraceae species, followed by in vitro embryo rescue of the immature embryo and subsequent regeneration. Again, medium composition and parental genotypes are important parameters. We evaluate CMS stability by controlled exposure to high temperatures and quantify the effect on fertility. Through RNA analyses and microscopic slides the development of flower buds in CMS and wild-type plants were compared.Relevance/Valorisation
At the end of the project the researchers can clearly state what worked and what didn't: Haploid chicory plants were succesfully induced upon pollination with a related Asteraceae species, and afterwards succesfully diploidized. Other classical in vitro techniques (ovule, anther or microspore culture) were not succesful. In terms of male sterility, 14 days after a heat shock, various CMS lines produced fertile pollen. The expression of most genes is similar in CMS and WT flower buds, but some differences were found. This was linked to the clearly aberrant flower bud formation that was visualised in the CMS microscopic slides.
The relevance of these results is clear. Belgium produces and processes more cichory than any other country in the world. The abovementioned techniques offer the potential to significantly improve the crop, particularly its inulin production.