Create new candidate hybrids. Sexual hybridization is completed between selected elite parents during spring flowering and seed collected in the fall. Selected hybrids are then grown-out for propagation, testing, and establishment of seed trees. Emphasis of current hybridization in the USDA rootstock program is among parents with superior tolerance to HLB, CTV, and Phytophthora, along with showing favorable effects on grafted tree yield, fruit quality, and tree size. US-942 and US-897 are two of the parents used in the most recent set of crosses with seed harvested in Oct 2019.Propagate and plant new field trials. Replicated multi-year field trials with commercial scions are essential to evaluate performance of rootstocks, both to determine whether each new rootstock should be released for commercial use, and to develop comparative performance information among new and existing rootstocks for a diversity of scions, soils, and management conditions. Because of the complexity of the new rootstock field trials, most USDA rootstock trials are propagated in the USDA citrus nursery in Ft. Pierce. Most of the rootstock field trials are planted with a single scion representing a common commercial type on each of 40-60 different rootstocks. Adequate replication is considered a critical factor in the USDA rootstock trials, with 6-7 replications the minimum and 12 replications the optimum to provide an acceptable level of reliability for results. Three new rootstock trials with promising rootstocks are being planted this fall. Nursery trees for four additional rootstock trials are being prepared in the greenhouse for planting in spring 2020.Collect data from field trials. Information collected from established field trials is collected by tree or by replication, and includes measurement of tree size, fruit crop, fruit quality, and pathogen titer, and assessments of tree health. Measurements related to cropping are on an annual cycle based on the scion, while measurements of health and tree size are on a schedule determined by the specific conditions and goals of the trial. There are currently 30 active USDA rootstock trials and containing about 300 new hybrid rootstocks being evaluated for potential release. Dr. Bowman is also a collaborator in many additional field trials for which data collection is managed by University of Florida researchers, and primarily funded by HLB-MAC Grants. Cropping data is being collected from 6 trials with early-maturing scions during Oct-Dec 2019.Posting field trial results for grower access. The USDA rootstock trials produce large amounts of information that is useful to identify the most promising of the new hybrids, as well as comparative information on the relative performance of many commercially available rootstocks. I recognize that this information is of great value to citrus growers and nurseries, and am working through several issues to post results from USDA rootstock field trials onto a website for easy access by Florida growers. It is anticipated that the first stage of that information will be posted to http://citrusrootstocks.org soon.