The project will focus on work to identify metabolite profiles associated with tolerance to HLB and other stresses in advanced rootstock selections, and validate the effectiveness of these metabolite profiles for selection by comparison of existing rootstock selections within the USDA program. As requested by CRDF, the project will place highest priority on work with new hybrid rootstocks already created, selected, and included in field trials. As requested by CRDF, other parts of the original proposal that involved integration with the breeding program, recurring selection, and discovery of biomarkers and antimicrobial compounds were eliminated, with a consequent simpler focus and smaller budget. In this quarter, data from a preliminary metabolomic study was organized and prepared for publication. This study was conducted under a previous CRDF funded grant, and demonstrated striking metabolic differences between HLB sensitive and HLB tolerant genotypes, both with and without Las infection. This data will serve as a foundation for continuing work under this grant. The work under this grant will focus on collecting an extended set of metabolomic data that will be adequate to allow validation of the approach by the end of project year 3. Environment may have strong effects on metabolomic data, so field testing, greenhouse testing, and information on seasonal variation will be critical for success in validating the approach. To clarify environmental effects, greenhouse studies will be needed, and a greenhouse suitable for the work is being constructed. In this quarter, plans were drawn up, and contract issued. The new greenhouse is expected to be completed in February 2016. In this quarter, plans for were made for specific studies to identify key metabolic compounds and collect the first stage of information to be used in the validation process. For the first year of the project, three greenhouse studies with potted trees, and five field studies (with established trees of different ages) will be conducted, to collect information about expression in leaf and root tissue, as well as seasonal effects on expression. The work will focus on 12 rootstocks that are of commercial importance and where previous studies have identified relative differences in tolerance to Las infection. Established field plantings are available with these 12 rootstocks suitable for the testing needed. In this quarter, trees in the selected field trials were scored for HLB symptoms and sampled for PCR testing, so that disease and infection status can be included in the choice of trees for metabolic testing. In preparation for the greenhouse studies, trees were propagated in another greenhouse, so that they can be moved into the new house for immediate experimentation, as soon as the new house is completed.