Ornamentals, tissue culture and gene technology

This group focuses on developing and implementing the latest plant breeding techniques. Emphasis is primarily but not exclusively on ornamental crops. Aspects of interspecific hybridisation, stress imposed by tissue culture conditions, control over recombination and genome editing by CRISPR/Cas9 are some of the main research targets.

The research is on developing protocols, and also in generating markers for marker assisted breeding in diploids and polyploids, to identify, isolate and edit genes by using genetic and genomic tools coding for traits of interest and to provide approaches in improving the quality of micopropagated plants. Development of plant half-material, amongst others, by interspecific crosses, is a major point of attention. The group is also involved in preparing science-based position papers for the government on the New Plant Breeding Techniques such as cisgenesis and targeted mutagenesis by CRISPR-technology.

Ornamentals

Ornamental breeding research is focussed on the development of tools for the efficient exploitation of genetic variation for the improvement of flower crops. Research projects have been directed towards biotic and abiotic stress tolerance, quality traits and assortment broadening by interspecific hybridisation and ploidy manipulation.

The genetics behind traits of interest for ornamental crops are studied by thorough monitoring of germplasm and phenotyping of mapping populations and association panels within newly developed trials. Emphasis is put on the assessment of determinants for complex traits. For complex traits or for traits that are costly or difficult to assess, linkage studies in progenies or association panels, either developed in house or by companies, are employed to identify molecular markers linked to specific traits or trait QTLs. This will allow indirect selection for these traits. The latest developments in Next Generation Sequence technology and High ThroughPut marker genotyping technologies are used for these mapping studies. Putative candidate genes for traits of interest are tested for co-localisation to earlier found QTLs. As most ornamental crops are characterized by their obligatory outcrossing nature and for a number of crops by higher ploidy levels, this requires the development of dedicated bioinformatics, marker scoring and mapping software, this in close interaction with other groups within Plant Breeding.

Interspecific crosses are made in order to introduce or generate new combinations of traits. Male and female fertility are monitored and pre- and post-fertilization barriers can be identified. Those barriers are studied and in many cases can be overcome technically, resulting in hybrids. Hybrid sterility can be overcome by ploidy manipulations but careful monitoring of interspecific hybrids for n or 2n gamete production is also performed. GISH is used to study levels of recombination in order to assess possibilities for introgression of desired traits into a recipient parent in backcrossing schemes.

Tissue culture

Plant tissue culture is an essential component of many present-day breeding techniques, such as anther culture, protoplast technology, embryo rescue and microsporogenesis.

Optimal conditions for such techniques are to be determined for each new species and we have a track-record in this area. Another major application of plant tissue culture is micropropagation: vegetative propagation in vitro. Micropropagation may produce very fast large numbers of vigorous plants with high quality and without endogenous pathogens. Micropropagation can be achieved by inducing outgrowth of axillary buds and suppressing apical dominance, by de novo synthesis of adventitous shoots or by somatic embryogenesis. Understanding the underlying mechanisms of some of the crucial steps in the processes mentioned above are studied aimed not only at improving the efficiencies, but also the quality of the plants produced. Because stress is a major cause of poor quality, quality improvement is tackled in a research project on stress related to tissue culture at the physiological, biochemical and molecular level. This should lead to practical solutions reducing the detrimental effects of stress imposed by the harsh environmental conditions in in vitro micropropagation. Another determining factor of growth and quality in tissue-cultured plants is nutrition. We are studying nutrient flows and parameters influencing it in tissue culture. The study of physiological factors as transpiration and photosynthesis is combined with a molecular genetic approach investigating the role of genes involved in carbohydrate partitioning.

Gene technology

Protocols for genetic modification of numerous crops have been developed based on the knowledge of processes involved such as regeneration, gene transfer, and DNA integration.

Research is aimed at constantly updating that knowledge and improving the efficiency with which genetically modified plants can be generated. As the potential for GM crops to be commercialized is limited within the EU, the technique of genetic modification is primarily used for gene function analysis or for testing functionality. However, we also explore the application of several "New Plant Breeding techniques' (NPBTs), in particular cisgenesis and genome editing in a number of crops. These NPBTs reduce the time and effort needed to create new crop varieties. CRISPR/Cas9 or CRISPR/Cpf1 are preferred intruments for genome editing aimed at inducing targeted mutations. Possibilities for using the same techniques for true genome editing by allele replacement are being explored. Developing transient expression systems, e.g. involving protoplasts or using recombinant DNA-free delivery systems to plant cells, is aimed at producing improved plant varieties, that are not regarded as GMOs. Field trials with cisgenic plants, e.g. apples, are carried out to monitor performance in the field of this category of products of NPBTs.

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Team

Researchers

Research assistants

PhD candidates