Whitefly resistant Poinsettia to reduce insecticide use
Whiteflies cause direct and indirect damage to Poinsettia plants by depleting them from photo-assimilates, by producing honeydew, and by vectoring viruses that can destroy a plant in a matter of weeks. The most important damage however is the presence of the insects or their eggs themselves, for which there is a zero tolerance in the market (trade).
Biological control and integrated pest management are widely used, with neonicotinoids being most important in management. However, whiteflies develop resistance to these and other insecticides. Also from an environmental point of view alternatives are needed.
Host plant resistance is a natural way of combatting insect problems. It enables the plant to resist insect invasions. Currently there is little knowledge about genetic variation for whitefly resistance in Poinsettia. Some differences in susceptibility among varieties have been observed, but there is no strong resistance identified yet. Strong resistance against insects is often found in wild relatives of the cultivated material. However, at present there is little knowledge about crossability of species related to E. pulcherrima. Also there is no knowledge on the mechanism(s) and genetics of the differences in susceptibility/resistance. This project aims to provide this information.
The main goals of the project are:
1) to identify novel sources of resistance against whiteflies that are crossable with E. pulcherrima
2) to study the genetics of resistance
3) to characterize the resistance mechanism(s)
The results will support the production of varieties that can be cultivated in a sustainable way, without or with far less insecticides than currently used. As such these varieties will contribute to the demand from society to reduce pesticide use. From a scientific point of view the project will increase our knowledge on the poinsettia-whitefly interaction and the possible role related species in poinsettia breeding.
The poinsettia, Euphorbia pulcherrima, also known as the Christmas flower is the most important pot plant worldwide. It has one big problem; it is susceptible to whiteflies. Growers have to use insecticides to control the whitefly population, which is undesirable from an environmental point of view. Poinsettia growers want to contribute to the societal demand for increasing sustainability. As the number of insecticides is rapidly decreasing the need for an alternative is urgent. They have to comply with pesticide regulations that become more and more strict. To be able to do this they need alternative ways to deal with the insect problem and host plant resistance is a promising alternative. Host plant resistance enables the plant to withstand insect invasions by either being unattractive (antixenosis) or by interfering with the life cycle of the insect (antibiosis), affecting development, increasing mortality and/or decreasing number of offspring. Currently there is little knowledge about genetic variation for whitefly resistance in poinsettia, although differences in susceptibility are observed by breeders. The companies involved in this project want to change this. They want to develop solid knowledge on genetic variation for whitefly resistance, and when present they want to elucidate the genetics of resistance and as far as possible obtain information on the mechanism. To increase the chances to find strong resistance plant materials from related species will be included. However, there is only limited knowledge on crossability among the related species, even for an important pot plant like poinsettia.
The project's concrete deliverables are:
1. A method for determining whitefly resistance in poinsettia, which should preferably be a high throughput.
2. Knowledge on resistance levels in materials made available by the companies involved, including the identification of plants highly resistant and susceptible to the whiteflies. Resistance may be identified in different sources.
3. Knowledge on crossability of the wild materials with E. pulcherrima, and if possible the genetics of resistance, a population segregating for whitefly resistance, information on QTL(s) and markers flanking the QTL(s).
4. Basic knowledge on the resistance mechanism
5. A paper in a scientific journal