In this project we are profiling the new scions and rootstocks for their tolerance to HLB by studying the metabolite content by GC-MS, and challenging new varieties with psyllids and HLB.Objective(s) pursued: 1. To understand the mechanism behind the tolerance of different varieties toward HLB. The comparison between the varietal responses will allow us to determine the mechanism of tolerance to CLas. 2. To understand the role of rootstocks in citrus tolerance to HLB. The comparison between rootstock metabolites will allow us to determine the best scion/rootstock combination for tolerating CLas. Progress on Objectives: This quarter we focused in three areas: 1) Marathon Mandarin analyses; 2) CUPS varieties; 3) Lucky biology and plant response.1) For the evaluation of the new mandarin hybrid Marathon, finally we have some cuttings that are growing in the greenhouse. In addition, the source plant is growing very well and we were able to sample many leaves for analysis of volatiles and polar metabolites. These samples have been run on the GCs and need integration.2) The samples from the new varieties we collected from the CUPS which were used for cuttings did not root well. It may be because we did this in the winter. They remain in the mist bed, except for UF 411 an UF 711 did root. The leaves collected for volatiles and metabolites are being prepared now for extraction (they must be diced into 0.1g aliquots). We estimate there will be approximately 150 samples for this phase. 3) For Lucky and its parents Sugar Belle and Nava x Osceola, we began the biology experiment (detailed in the previous report) on 11/30/20 and ended it Jan 30th, which was one month longer than planned because the weather during December was so cold, we did not have good colonization. We ended the experiment by collecting leaf samples from all plants to assess the plant response to ACP, sprayed any remaining insects, and returned them back to their outside cage to recover. The plants did not look well, so we trimmed, repotted and fertilized them. The leaf metabolites from the ACP-exposed plants will be compared to non-infested controls.In addition to these efforts, the seeds from the USDA (US-802, 812, 897, 942, 1283, 1284, 1516) for metabolite profiling and HLB screening were received, planted, and the germination rate was good. It will be some months however before we can do anything with them in terms of sample collection.