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Late blight is an important disease in potato that is caused by the oomycete Phytophthora infestans. In the past, Solanum demissum late blight resistance (R) genes were introgressed into cultivated potato (Solanum tuberosum). Eleven of these resistant plants were selected to characterize the virulence spectrum of individual P. infestans isolates and to monitor the dynamics of virulence in P. infestans populations. These plants are referred to as the Mastenbroek and Black differential sets. It has long been assumed that each differential plant contained one single R gene. In the current study and previous studies, however, most Mastenbroek differential plants were shown to harbor multiple R gene(s), which blurs virulence typing of late blight isolates. In order to acquire more accurate virulence profiles, we extended the Mastenbroek differential set with Solanum spp. plants harboring reduced R gene complexity and with plants containing recently identified R genes from related but different Solanum species. In addition, a differential set of ten Genetically Modified (GM) plants harboring single late blight R genes in the same genetic background (Desiree). By analyzing the virulence spectra of recently collected isolates using both newly described differential sets, we found that the GM Desiree differential set was more accurate for isolate virulence typing than the conventional (extended) differential set. Besides, the GM Desiree differential set was shown to be useful as trap plants to isolate novel P. infestans strains and to monitor virulence towards particular R genes in P. infestans populations `on site´. Legislative restrictions are, however, limiting the use of the GM Desiree differential set.

Background Piercing-sucking insects cause severe damage in crops. Breeding for host-plant resistance can significantly reduce the yield losses caused by these insects, but host-plant resistance is a complex trait that is difficult to phenotype quickly and reliably. Current phenotyping methods mainly focus on labor-intensive and time-consuming end-point measurements of plant fitness. Characterizing insect behavior as a proxy for host-plant resistance could be a promising time-saving alternative to end-point measurements. Results We present a phenotyping platform that allows screening for host-plant resistance against Western flower thrips (WFT, Frankliniella occidentalis (Pergande)) in a parallel two-choice setup using automated video tracking of thrips behavior. The platform was used to establish host-plant preference of WFT with a large plant population of 345 wild Arabidopsis accessions and the method was optimized with two extreme accessions from this population that differed in resistance towards WFT. To this end, the behavior of 88 WFT individuals was simultaneously tracked in 88 parallel two-choice arenas during 8 h. Host-plant preference of WFT was established both by the time thrips spent on either accession and various behavioral parameters related to movement (searching) and non-movement (feeding) events. Conclusion In comparison to 6-day end-point choice assays with whole plants or detached leaves, the automated video-tracking choice assay developed here delivered similar results, but with higher time- and resource efficiency. This method can therefore be a reliable and effective high throughput phenotyping tool to assess host-plant resistance to thrips in large plant populations. Electronic supplementary material The online version of this article (doi:10.1186/s13007-016-0102-1) contains supplementary material, which is available to authorized users.