EFFECT OF PRODUCTION SYSTEM ON TOMATO FRUIT QUALITY AND LEAF METABOLITE PROFILE CHANGES IN RESPONSE TO BACTERICERA COCKERELLI-CANDIDATUS LIBERIBACTER SOLANACEARUM INSECT-PATHOGEN COMPLEX
Date
2019-12-03
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Abstract
Tomato (Solanum lycopersicum) is one of the most widely consumed horticultural crops in the world, and an important source of multiple health-promoting compounds. Fresh and processed tomatoes have huge demand globally, and the fruit qualities will influence consumers’ preferences and market value. Consequently, to improve the yield, quality and health-promoting compounds, controlled production systems such as hightunnel (HT) and disease resistant genotypes have been studied. This dissertation mainly focuses on two main objectives: the first is to evaluate the effect of production systems on tomato qualities associated with health-promoting compounds. The second is to elucidate the distinct profiles of susceptible and resistant tomato genotypes against Bactericera cockerelli, tomato potato psyllid (TPP), vectoring or not the phloem-limited bacterial pathogen Candidatus Liberibacter solanacearum (Lso). The first two studies, determined the effect of production systems (net-house (NH) and open-field (OF)) on volatile profiles using optimized headspace solid phase microextraction (HS-SPME) conditions (2g fresh weight (FW), a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber at 60 °C for 45 min) for extraction. About 40 volatile metabolites were identified using gas chromatography coupled with a mass spectrometer (GC-MS) and relatively quantified in four tomato varieties grown in north Texas (Amarillo) and eight tomato varieties grown in south Texas (Weslaco). The levels of flavor-associated β-damascenone, geranylacetone, and d-limonene were significantly affected by production systems.
In the third, fourth, and fifth studies, the eight different varieties of tomatoes, including three Texas A&M University (TAMU) and five commercial varieties were grown in Weslaco to examine the in vitro bile acids binding capacities and the levels of health-promoting compounds, including ascorbic acid, carotenoids, phenolics, indole amines, as well as quality-associated enzymes polyphenol oxidase (PPO) and peroxidase (POD). Effect of production systems was evaluated by ultrahigh performance liquid chromatography (UPLC) coupled to quadrupole time-of-flight high-resolution mass spectrometry (QTOF-HRMS) combined chemometric analysis to understand the differential effect based on genetics. Lastly, the changes of metabolic profiles of insect-susceptible (cv CastleMart) and -resistant (RIL LA3952) genotypes were evaluated by HS-SPME/GC-MS and UHPLC/APCI‐QTOF-HRMS. Furthermore, multivariate analysis using partial least squares-discriminant analysis (PLS-DA) distinguished the resistant tomato genotype response to TPP carrying or not the pathogen by confirming response volatile compounds.
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Keywords
Tomato, Production system, High-tunnel, Open-field, Ascorbic acid, Carotenoids, Phenolics, Indoleamines, Volatiles, Tomato-potato psyllid, Candidatus Liberibacter solanacearum.