Create new candidate hybrids. Seedlings from 2019 crosses continued to be grown-out in the greenhouse in preparation for propagation, testing, and establishment of seed trees. Selections were made from 2018 cross seedlings and prepared for making cuttings to enter into Stage 1 trials. Emphasis of hybridization in the USDA rootstock program is among parents with superior tolerance to HLB, CTV, and Phytophthora. Some of the best performing of the newest hybrids in Stage 1 field trials are hybrids of US-942.Propagate and plant new field trials. Budwood increase trees of selected scions were grown, in preparation for budding trees for new rootstock trials. Four new replicated field trials were planted in St. Lucie County this quarter, at Stage 1 trial with Valencia orange, and Stage 2 trials with Bearss lemon, Eureka lemon, and Washington Navel orange. Other planned plantings were delayed because of institutional Coronavirus shutdown. Nursery trees for Stage 2 rootstock trials with Valencia orange, Hamlin orange, and Star Ruby grapefruit are being prepared in the greenhouse for field planting in 2021.Collect data from field trials. Information on tree performance is collected from established field trials, and includes measurement of tree size, fruit crop, fruit quality, and pathogen titer, HLB symptoms, and assessments of tree health. Cropping data is collected during the time of scion harvest, and this quarter was not the time for cropping data with any of the trials. Assessments of tree health and measurements of tree size were completed on 3 trials during this quarter, which was reduced from the normal because of the institutional Coronavirus shutdown. Assessments of brix, acid, and color for the fruit quality analysis of last season data from Stage 1 and Stage 2 trials resumed this quarter after being on hold during the institutional Coronavirus shutdown the past 6 months. The pace of working through his backlog of fruit quality assessments will be slow because of continuing institutional Coronavirus restrictions, and the influx of new fruit quality assessments on the new season crop that begins in the coming weeks.Evaluate effectiveness for seed propagation of new rootstocks and develop seed sources. Some of the newest hybrid rootstocks can be uniformly propagated by seed, but others cannot. As the best rootstocks are identified through testing, seed sources are established and used to determine trueness-to-type from seed. Studies were continued this quarter to evaluate seed propagation for 25 of the most promising SuperSour hybrid rootstocks. SSR analysis of progeny is progressing more slowly than planned because of institutional Coronavirus shutdown and restrictions.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. During this quarter, updated summaries for five trials were prepared for uploading to the website https://www.citrusrootstocks.org/. Release of superior new rootstocks for commercial use. Several of the 350 advanced Supersour rootstock hybrids in field trials are exhibiting good performance in comparison with the commercial standard rootstocks. Performance data continues to be collected, but it is anticipated that 2-3 of the most outstanding of these will be officially released in 2021-22. Release of new rootstocks is based on the summation of performance in field trials over multiple years, including information on tree survival and health, canopy size, fruit yield and fruit quality, and observations on tolerance of disease and other biotic and abiotic threats.