## 1 Introduction  
The phloem-limited bacterium '_Candidatus_ Liberibacter solanacearum' (Lso) is vectored by the tomato-potato psyllid (TPP, _Bactericera cockerelli_), causing severe symptoms on Solanaceae crops, including Zebra Chip disease in potato (_Solanum tuberosum_) and vein greening in tomato (_Solanum lycopersicum_) [1, 2, 3]. Some wild tomato relatives as germplasm resources have been screened for polygenic resistance traits against the TPP [4]. Particularly, several major quantitative trait loci (QTLs) related to adult TPP mortality and fecundity were confirmed in _Solanum habrochaites_ using recombinant inbred lines (RILs) [5]. Major resistance QTLs found in the RIL LA3952 carrying the S. hhrochaites insertion on chromosome 8 revealed that the presence of Lso is associated with increased adult TPP mortality, while the reduced TPP oviposition trait in LA3952 is independent of Lso [5].  
Thus far, substantial genomic analysis has underscored the influence of the TPP-Lso complex in potato and tomato genotypes [6; 7; 8; 9], and constitutive and elicited phytohormones, such as jasmonic acid and salicylic acid have been reported to play crucial roles in the host plants by deploying defensive signaling pathways involved in the host resistance against insect herbivores and pathogens [6; 7; 8; 9]. For instance, volatile metabolites, such as monoterenes play a role in response to insect herbivory by attracting carnivorous predators as an indirect plant defensive mechanism [10; 11; 12]. Conversely, the phenolic p-coumaric acid inhibits the type III secretion system (T3 SS) virulence genes of the gram-negative plant pathogen _Dickeya adandtii_[13]. For phytohormones, their regulation varies, and may be specific to host and pathogenic strains [14]. To fully understand this may require that the response to stress by the vast majority of metabolites and phytochemicals be delineated and if possible, be predictable enough to enable the long-term application in resistance breeding programs. Little information is known about responses of susceptible and resistant tomato genotypes to the TPP carrying Lso pathogen [9; 15; 16]. Metabolomics approaches using liquid chromatography (LC) and gas chromatography (GC) coupled with mass spectrometry (MS) are some of the effective present-day tools for identifying and quantifying plant metabolites, including phenolics, phytohormones, volatile organic compounds (VOCs), in the induced response to pathogens and screening potential biomarkers [17; 18; 19].  
Herbivore-induced changes of metabolite profiles could be influenced by several factors, including developmental the presence of the pathogen, stages of plants, insect species, infestation pressure, and different periods after inoculation [20; 21; 22; 23]. The added intervention of the pathogen has created a complex interaction between host, insect, and pathogen [24], which is worth multifaceted studies in order to improve our understanding of the plant's innate immune responses to vector colonization and pathogen infection [9; 16; 19]. In the present study, we report a comparative tomato metabolic profile in response to TPP carrying the Lso pathogen or not in resistant and susceptible tomato genotypes in order to identify putative metabolites involved in defensive signaling in the TPP-Lso-tomato complex interaction.