Tospoviruses remain a major threat of crops with an extensive host range (> 1,000 plant species) and worldwide distribution. This virus family is notorious for the devastating effects on crops and ornamental plants with losses reaching more than 100 M€ per year (Rotenberg et al., 2015). Tospoviruses can exchange genomic segments through re-assortment during co-infections. Consequently, new viral species emerge constantly, which further extents the host- and geographical-range of this virus family (Tentchev et al., 2011). These viruses are transmitted by thrips—tiny polyphagous insects that are pests of many plant species including relevant crop and ornamental species. Chemical control of this vector insect with insecticides has poor efficacy due to their small size, behaviour, and ability to develop resistance at a population level to all major chemical classes. In the meantime, these persistent insecticides contaminate our soils and ground/surface waters, thereby exerting a strong negative impact on our ecosystems and biodiversity (including pollinators). Therefore, the use of many chemicals will be banned in the coming decade by EU policies, resulting in a high demand for genetic (breeding) solutions in crops to tackle this tripartite problem.
Disease management is best achieved by breeding for plant disease resistance. Thus far, two resistance genes against tospoviruses were successfully identified and introgressed in crops (Tsw in Pepper; Sw-5b in tomato), but these are now broken in different geographical regions (Turina et al., 2016; Zhu et al., 2017). To tackle this societal and economical challenge, we propose the continuation of an integrated research program on the virus, its plant host, and its vector. We will use our proven strong consortium to (i) further develop and mine the knowledge and data sets generated, to (ii) explore and apply alternative methods where these are not yet available and importantly, (iii) validate the identified susceptibility targets in planta through generating mutant material to study the underlying molecular mechanisms and validate the role of candidate S-gene targets in viral replication and vector performance.
Understanding the underlying mechanisms allows the industry partners to screen themselves for genetic variation and create novel crops that exhibit factors that modulate the virulence of plant viruses to compromise vectored viral transmission. Our ambition in this Phase 2 remains to provide leads to convert a host plant into a non-host. Our multi-layered pest management strategy aims to reduce viral spread in case that one of the introduced defence layers is overcome by a new viral strain. Hence, the strategy provides durable resistance in crops against tospoviruses. To reach our goal, we will study already obtained data in Phase 1 to identify and validate anti-viral proteins. We will study cross-kingdom interactions between host, viral vector and the virus and elucidate the molecular mechanisms of insect effector proteins and RNAs from thrips saliva, that we have identified, in the interaction with their in planta-targets to manipulate defence.

Validation and molecular elucidation of resistance traits and the development of key technologies for plant breeders to implement novel resistance mechanisms to combat pests-insects and the viruses they carry.

This project contributes to the objectives of the KIA “Agriculture, Water and Food” with its ambition to develop knowledge, innovation and application in public-private partnerships within the domain: agriculture, water and food (i.e. domain 4). This knowledge and innovation agenda focuses on healthy food supply fitting the long-term ambitions fitting to the proposal.

Deliverables: developing know-how and technology to support disease and pest resistance breeding