Objective 1. Identify key metabolites that are associated with rootstock traits. Accomplishments: Metabolite profiles of rootstock seedlings of ten rootstock cultivars in two separate experiments were assessed for primary metabolites in collaboration with West Coast Metabolomics Center (WCMC), UC-Davis. Results from the original study were published (Albrecht, Fiehn, Bowman. Plant Physiology and Biochemistry 107:33-44). The data obtained are large and complex and are being used for additional detailed analysis. An additional manuscript was submitted to Plant Physiology and Biochemistry in this quarter. An excerpt from this analysis is shown below. Objective 2. Investigate the effect of grafting on metabolite profiles. Accomplishments: Eleven rootstocks were analyzed as greenhouse and field-grown grafted trees in combination with Valencia and other scions. Samples were submitted to WCMC for analysis, and metabolic profiles of leaves and roots of the grafted trees are being compared. These studies will aid in identifying rootstock-scion interactions. The data sets are large and complex, but a publication is expected to be submitted in the next few months. Objective 3. Establish metabolite profiles of trees on different rootstocks in response to HLB. Accomplishments: An experiment consisting of 300 trees of Valencia grafted on ten rootstocks and grown in greenhouses was completed. Trees were inoculated with Las. Leaf and root tissue of Las-infected and uninfected plants were collected at 30 weeks after inoculation. Samples from these experiments were sent to WCMS for GC-TOF-MS analysis of primary metabolites and secondary metabolites in 2017. Partial results have been received, with the remaining results expected soon. Results from these analyses are being used for detailed analysis of metabolite profiles associated with HLB. A publication of the results is being prepared. Additional information is available on request.