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Thesis

English

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http://hdl.handle.net/10251/150069

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Introgression of Ty resistance genes from wild relative species S. chilenseinto tomato: genomic and metabolic effects

Abstract

[EN] In previous studies, the FGB lab have shown that when a fragment from Chromosome 6 of Solanum chilense (which contains Ty1-3 resistance genes) is introgressed into tomato (Solanum lycopersicum), the fruit volatile profile is affected. Our working hypothesis is that a S. chilense FAD gene located next to the Ty gene is also introgressed -causing a higher expression of FAD, which is translated into a higher synthesis in fruit of volatiles produced from double-bond Fatty Acids through the Lipoxygenase Pathway. The objective of this thesis is to analyse further the effect of this S. chilense introgression by 1) determining if the change in volatiles production is restricted to tomato fruit or affects also leaves, 2) defining the differences at the genomic level between the FAD gene from tomato and S. chilense, and 3) performing a literature review to check on the extent linkage drag has on tomato breeding. We first analysed the VOCs present leaves of Solanum lycopersicum cv. Muchamiel and De la Pera traditional varieties, that either contain or not the Ty resistance gene introgression from S. chilense. We performed a SPME-HeadSpace Gas Chromatography-Mass Spectrometry analysis in order to capture, separate and quantify the volatiles present in our samples. We conducted a Targeted Metabolic Analysis to analyse possible differences in 15 specific compounds and an Untargeted Analysis to analyse all chromatograms¿ data. Results indicate no changes in the Fatty Acids-derived volatiles in leaves, indicating that the effect of the introgression could be restricted to fruit. Moreover, we performed a molecular analysis of the FAD gene sequence in both tomato and S. chilense, concluding that there is a 700bp-long repetitive element present in the promoter of the FAD gene in tomato which is absent in S. chilense species. In order to assess which alterations in the promotor sequence cause the FAD gene to present a higher expression in S. chilense than in tomato, we performed a bioinformatic analysis using the PLACE database and the informatic programs Nsite-PL and NsiteM-PL from the RegSite Database. While this repetitive element disrupts a couple of regulatory domains of the promoter, additional reasons for downregulation could be the hypermethylation of the promoter region in tomato. As this FAD gene is also required for the synthesis of Jasmonate phytohormones, aliquots of our samples are ready for future hormone analysis, since these are important for induction of defense systems in the plant. In order to assess this aspect, our samples were punctured with the zoophytophagous mirid bug Nesidiocoris tenuis and will then be compared with the control samples. Literature review identified a number of cases in tomato breeding where introgression of disease resistance genes has an effect on other traits of the plant due to linkage drag. A review of the most cultivated tomato F1 hybrids indicated that most of them carry more than three introgressions from wild relative species and are, therefore, likely to be affected regarding other traits, either beneficially or not, which ultimately affects consumer liking. Sendra Ortiz, A. (2020). Introgression of Ty resistance genes from wild relative species S. chilenseinto tomato: genomic and metabolic effects. http://hdl.handle.net/10251/150069 TFGM

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