Host plant resistance of tomato plants to western flower thrips

Abstract

This thesis explores the resistance of tomato plants to WFT. At first an overview about tomato, WFT and their interactions is presented (this chapter). This is followed by 5 experimental chapters. The first experiment comprises a comparison of thrips resistance between major tomato cultivars and wild tomatoes. Wild species of crops are important sources of genes for resistance to biotic and abiotic stresses. In this study, we explored the natural variation in WFT resistance of the genus Lycopersicon by performing bioassays and comparing thrips damage on some wild species and cultivated lines to determine the chemical and mechanical resistance factors in these plants. All plants were subjected to NMR metabolomic analysis to correlate thrips resistance to plant secondary metabolites (Chapter 2). Invasion of pests may lead to rapid local adaptation and the development of biotypes specialized to different hosts. Therefore, host plant adaptation of thrips was studied by observing variation in genetics and performance of Dutch WFT populations (Chapter 3). In this chapter genetic differences between Dutch WFT populations collected on different hosts were analysed with AFLP and the existence of possible cryptic species was tested using mitochondrial barcoding. Feeding damage and reproduction of thrips were examined in different thrips bioassays. A negative effect of CGA in chrysanthemum on WFT has been reported earlier. To study the effects of CGA level in tomato on thrips resistance, transgenic tomatoes with increased amounts of CGA were subjected to thrips infestation and feeding damage was monitored (Chapter 4). Introgression lines (ILs), represent an excellent platform to explore the genetics of multiple biological and chemical traits of agronomical importance. The wild tomato, S. pennellii was highly resistance to WFT (Chapter 2). A set of 76 introgression lines between the S. pennellii and the cultivated tomato S. lycopersicum was used to detect QTLs associated with WFT resistance, secondary metabolites and their co-localization (Chapter 5). Sugars have acted as plant hormones that control gene expression and development processes in plants and sugar spraying of leaves has been used in pest management of different plants. Potentially, it can, therefore be used as a new and more environmentally friendly method of crop protection. We used sugar-sensing, applying sprays of sucrose, fructose and glucose to increase resistance to WFT in a susceptible tomato cultivar (Chapter 6). The summary and conclusions of this thesis are given in chapter 7.