Objective 1. Collect field performance data from Stage 1 and 2 replicated rootstock field trials and release new rootstock cultivars as justified by superior performance in multiyear field trials. Collect field performance data. Three of the 31 established replicated trials listed (Appendix ix. Table 1) on the original proposal were determined to be complete, and were removed (WFF 2011, WFF 2012, WFF 2014 HB). During this quarter, canopy health data was collected from all trees in the other 28 active rootstock trials. Collection of brix and acid fruit quality data was completed during this quarter for the 2022 season on the active Valencia trials by using frozen juice samples. Supplemental testing of promising selections. When rootstock selections appear promising in field trials and are being considered for commercial release, additional information about stress tolerance is highly desired. This will help inform appropriate sites and management for commercial use. During this quarter, rootstock plants were propagated in preparation for a study to evaluate salinity tolerance among selected promising new rootstocks. During this quarter, rootstock plants were also propagated in preparation for a study to evaluate sting nematode tolerance among selected promising new rootstocks (primarily funded by a different CRDF grant). Preparation for release. Uniform seed propagation is not a requirement for new rootstocks, but is a highly desired trait for convenience of propagation. During this quarter, work continued to evaluate uniformity from seed for the most promising SuperSour hybrids, some of that in collaboration with Dr. Albrecht and a graduate student. In the past, the FDACS budwood program has cleaned up and maintained a large number of USDA rootstock selections during the field testing process and in preparation for commercial release. That FDACS program has announced changes that would mostly remove USDA rootstock holdings that are not already commercially used, which will require some significant adjustments to the USDA preparations for rootstock release. How that will be managed is still being sorted out.Release of new rootstocks. New rootstocks will be officially released by USDA for commercial use when justified by multi-year performance in the early-stage replicated field trials. Based on outstanding performance in field trials, the proposed release documentation is being prepared for three new USDA rootstocks. New USDA clones are assigned official names at release, and these new names have not yet been approved. Objective 2. Create hybrid rootstocks that combine germplasm from parental material with good rootstock traits and HLB tolerance, propagate the most promising of these hybrids, and establish replicated field trials with commercial scions. Create hybrids. Current focus of USDA rootstock work is on testing of hybrids previously created, and with funding uncertainty, no new hybrids were created in spring 2022. New crosses are planned for spring 2023, with parental combinations based on new information and breeding values of particular clones assembled over the past year. Propagate hybrids. New hybrids to be used in trials will be propagated by uniform nucellar seed or stem cuttings. Plant material was prepared in the nursery for three new Stage 2 trials, including commercially available rootstocks and the most promising of the new SuperSour hybrids. It is anticipated that these trees will be ready for field planting in spring 2023. Establish replicated field trials. Two new replicated field trials were planted this quarter, one is a Stage 2 trial with Hamlin scion at the Whitmore Farm in Lake County, and the second is a Stage 1 trial with Valencia scion at a collaborator site in Desoto County. These will be added to the list for field performance data collection.