Chrysanthemum is an important ornamental plant, but its cultivation suffers heavily from thrips infestations. To reduce pesticide use, resistant varieties are needed. In this project, we study previously identified (wild) Chrysanthemum accessions that are resistant to multiple thrips species. We will elucidate the genetics of resistance and identify resistance-causing metabolites. Doing so, we will generate knowledge and breeding tools to effectively breed for thrips-resistant varieties.

The project will result in several tools that will benefit breeders and growers of Chrysanthemum: 1) Identified sources of broad-spectrum resistance to thrips and other pest insects, 2) Genetic markers to introgress this resistance in varieties, 3) Information on metabolites that lead to resistance in Chrysanthemum. This will ultimately contribute to more sustainable production of chrysanthemum with less (if any) input of pesticides.

This project contributes to ST2, Biotechnology and breeding, as it aims to generate the knowledge and tools necessary to develop chrysanthemum varieties with resistance against thrips. To achieve this goal, we will generate knowledge on resistance mechanisms and loci in cultivated and wild Chrysanthemum. We will identify molecular markers, that can be used by participating breeding companies to introgress these resistances into cultivated varieties. Information on metabolites leading to resistance may be used to further identify resistant varieties. Knowledge generated in the project will thereby form the scientific basis for the production of novel varieties that have natural resistance to insects. Moreover, we include multiple thrips populations and species in our research, and assess resistance to other insect pests as well, to achieve a broad-spectrum and durable resistance. In this way, it contributes to MMIP A2, of which the objective is more resilient varieties, especially with resistances against multiple species. The ultimate aim is sustainable production of chrysanthemum with less (if any) input of pesticides.

The deliverables of this project include:
1. Information on the genetics of resistance in a Chrysanthemum morifolium cultivar, including identified QTLs, QTLs effects and flanking markers to introduce the resistance in breeding programs (expected in 2025)
2. Knowledge on broad-spectrum resistance to different pest insects in wild Chrysanthemums (2025),
3. An artificial diet method that can be used to validate metabolites involved in resistance against thrips (2025).
4. Information on the resistance mechanisms in (wild) Chrysanthemum to thrips. (2026),
5. Identified metabolites that reduce thrips survival and lead to resistance in thrips.
6. Information on metabolites leading to resistance may be used to further identify resistant varieties (2026-2027),
7. Knowledge of possible interference of resistance with currently used biocontrol agents (2026-2027).
8. Identified resistance QTLs from wild relatives of Chrysanthemum, QTLs effects and flanking markers (2027) and
9. Plant material with improved resistance characteristics (2028).
Results of the project will be presented at consortium meetings and conferences and will be included in papers in scientific journals.