Generation and Characterization of Tomato Lines with Modified Acylsugar and Fatty Acid Profiles John Reid Smeda PhD
Cornell University, 2017 Acylsugars are accumulated by several wild relatives of tomato and are implicated in mediating a variety of defensive plant-insect interactions. Acylsugars are produced at high levels by glandular trichomes of Solanum pennellii and the ability to produce acylsucrose acylsugars at elevated levels was previously bred into tomato using S. pennellii (Correll) D’Arcy accession LA716, leading to the creation of the benchmark line CU071026, which exhibits an acylsugar chemotype profile distinct from that of S. pennellii LA716. Four QTL previously associated with changes in fatty acid profile (FA2, FA5, FA7, and FA8), were individually combined with the five introgressions of CU071026. Characterization of the resulting lines indicated alterations to acylsugar level and acylsugar chemotype by modulating the length, orientation and/or relative proportion of fatty acid acyl groups, leading to changes in overall acylsugar composition. The combinatory effect of three of the QTL (FA2, FA7, and FA8) on acylsugar level and chemotype was evaluated by combining these QTL. Characterization of the resulting lines demonstrated that the fatty acid QTL interacted additively and epistatically to alter acylsugar level and chemistry, increasing the diversity of acylsugars accumulated. The acylsugar level and chemotype traits of the lines generally displayed high heritability and minimal environmental interaction.
Three acylglucose QTL (AG3, AG4, AG11), previously associated with control of acylsugar moiety, were utilized to generate lines with acylglucose accumulation. Two approaches were taken to generate these lines and characterization demonstrated that epistatic interactions among the three acylglucose QTL controlled acylsugar level and acylglucose accumulation and that the three QTL can result in moderate levels of acylglucoses, but that an additional QTL might be needed for high acylglucose accumulation. Additionally, characterization of the acylsugar chemistry revealed impact of the acylglucose QTL on the composition of accumulated acylsucroses, and potential impact on the fatty acid composition. The knowledge and the germplasm from this dissertation will support the generation of high acylsugar-accumulating tomato lines and hybrids with increased acylsugar profile diversity. This germplasm can also contribute to elucidation of the mechanism of insect resistance mediated by acylsugars, and assist with identification of yet-unknown acylsugar synthesis genes.