Supplement to HortScience Volume 55(9) September 2020 This supplement contains the abstracts of presentations from the following National Conference and Regional Meetings of the American Society for Horticultural Science ASHS Annual Conference August 10-August 13, 2020………………………………………………S1 Southern Region-ASHS Annual Meeting January 31–February 2, 2020, Louisville, KY………………….S376 Northeast Region-ASHS Annual Meeting January 6-January 9, 2020, Philadelphia, PA…………………………….S436 Please note that abstracts from the 2020 Northeast Region-ASHS Annual Meeting are reprinted with permission from the “PROCEEDINGS – VOLUME 5, THE NORTHEASTERN PLANT, PEST, AND SOILS CONFERENCE, 2020.” And can be accessed online at https://neppsc.org/wp-content/uploads/2020-NEPPSC-Proceedings-FINAL.pdf For best viewing, the supplement should be downloaded in its entirety to your computer. It is best viewed using Adobe Acrobat Reader American Society for Horticultural Science 1018 Duke Street Alexandria, VA 22314 phone: 703-836-4606 fax: 703-836-2024 ashs.org [email protected] Abstracts of Presentations from the Annual Conference of the American Society for Horticultural Science 10 August–13 August, 2020 Supplement to HortScience Volume 55(9), September 2020 Day 1: Monday, August 10, 2020................................................S2 Day 2: Tuesday, August 11, 2020...............................................S52 Day 3: Wednesday, August 12, 2020.........................................S179 Day 4: Thursday, August 13, 2020..............................................S285 For citation purposes, abstracts should be cited as shown in the following example: Bachman, G.R., Coker, C.E.H., and Knight, P.R. 2020. Horticulture CSI: The Latest Clues in the Search for the Long Beach Red Radish. HortScience 55(9) S8. (Abstr.) American Society for Horticultural Science 1018 Duke Street Alexandria, VA 22314 phone: 703-836-4606 fax: 703-836-2024 ashs.org [email protected] —Workshops— Part 1: Workshops/Special Sessions Day 1: Monday, August 10, 2020 8:00 AM – 10:00 AM tion, chlorophyll content, and other components of growth were measured. Cuttings began to grow at Citrus Crops 1 two weeks when supplemental light was provided to increase day length, at three weeks in the night Moderator: Sameer Pokhrel, University of Florida interruption treatment and at five weeks when no supplemental light was provided. The responses to 8:00 AM Propagation of New Citrus Root- supplemental light differed among the rootstock cul- stocks by Stem Cuttings during the Winter tivars. Our results indicated that use of supplemen- with LED Supplemental Lighting tal LED lights to irradiate citrus cuttings significantly Rayane Barcelos Bisi*, Southwest Florida Research reduced the time required for both root formation and Education Center, University of Florida/IFAS and and subsequent plant growth. The presented infor- USDA-ARS; Ute Albrecht, Southwest Florida Research mation will be of significant value for researchers and Education Center, University of Florida/IFAS and and commercial nurseries involved in the propaga- Kim Bowman, USDA-ARS tion of rootstock cultivars. Abstract: The rootstock is an important component Specified Source(s) of Funding: Citrus Research and of the modern citrus tree, influencing the fruit yield, Development Foundation fruit quality, tree size, and tolerance of a wide range of adverse environmental conditions and disease threats. Because of the spread of huanglongbing 8:15 AM Comparison of Field Performance disease (HLB) and consequent decline of the Florida of Citrus Trees on Rootstocks Propagated citrus industry, new hybrid rootstocks with improved By Seedling, Cuttings, and Tissue Culture tolerance to HLB were released by the USDA citrus Sameer Pokhrel*1; Adam Hoeffner1; Kim Bowman2 breeding program, including ‘US-1281’, ‘US-1282’, ‘US and Ute Albrecht3, (1)Southwest Florida Research and SuperSour 1’, ‘US SuperSour 2’, and ‘US SuperSour 3’. Education Center, University of Florida/IFAS, (2)US- Due to the urgency for solutions to the HLB threat, DA-ARS, (3)University of Florida/IFAS these rootstocks were propagated by stem cuttings Abstract: The bacterial disease Huanglongbing (HLB) for testing, and seed propagation was not evaluat- is causing devastation in most citrus groves through- ed in advance of release. Subsequently, SSR markers out the world. Since no cure for the disease has been were used to evaluate seedlings, and no true-to-type discovered yet, growers are relying on different man- seedlings were recovered for three of these root- agement strategies to mitigate the impacts of HLB in stocks, indicating that economical seed propagation citrus production. One of such strategies is the use is impossible for these clones, and that commercial of tolerant rootstock cultivars. Several studies have use will require propagation by stem cuttings or mi- found that superior rootstock cultivars can signifi- cropropagation. The other two of these new root- cantly enhance the performance of the grafted scion stocks have not yet produced seed, and consequent- in an HLB endemic environment. Traits associated ly the potential for seed propagation is unknown. with the root architecture and the regeneration ca- With a goal to improve the successful rooting of pacity of roots are probable factors associated with stem cuttings for these and other similar rootstocks, HLB tolerance. Traditionally, citrus rootstocks are we initiated a study to evaluate the effect of supple- propagated by seed because it is cheap and because mental LED light on stem cutting propagation during of the phenomenon of nucellar embryony, which al- winter short days in the greenhouse. Two other lows the production of genetically uniform plants. As rootstocks (‘Swingle’ and ‘US-942’) were included in the demand for HLB tolerant rootstocks is increas- the study as a commercial standard and because of ing, seed supplies are inadequate, and growers are high commercial demand combined with a shortage often unable to obtain enough trees on the most de- of seed for propagation, respectively. Treatments sired rootstock cultivars. In addition, since no seed compared were 1) no supplemental light, 2) low in- source trees are yet available for some of the new- tensity LED light to increase day length to 16 hours, er rootstocks, vegetative propagation is required to 3) high intensity LED light to increase day length to meet the demand. This study explores the potential 16 hours, and 4) night interruption with low intensi- of rootstocks propagated by tissue culture and cut- ty LED light. Vegetative shoot growth, root produc- tings for use in commercial citrus production. Two I lksjdflkjasldfkj An asterisk (*) after a name indicates the presenting author. S2 HortScience 55(9) Supplement – 2020 ASHS Annual Conference trials were established in 2018, one each in Hendry a poorly drained flatwoods-type site in Highlands and Polk County, Florida. Each trial includes 3 (Polk County and included 32 different rootstocks. Trial 2 County) or 4 (Hendry County) commercially import- was established on a well-drained sandy site in Polk ant rootstock cultivars propagated by seed, cuttings County and included 30 different rootstocks. The and two different methods of tissue culture. The ex- rootstock cultivars included in this study have a wide periment was designed as a randomized split-plot, range of genetic backgrounds. Whilst some of them with rootstock cultivar as the main plot factor, and are already commercially available in Florida, Califor- method of propagation as the sub-plot factor. All nia, and Spain, others are not yet released. The ex- rootstocks were grafted with ‘Valencia’ (Citrus sinen- perimental design was completely randomized with sis) scion. The objective was to investigate the effects 6 replicated plots of each rootstock and 8 trees in of rootstock propagation method, rootstock cultivar, each replicated plot. Horticultural traits such as tree and their interaction on tree performance during height, canopy spread, rootstock and scion trunk di- the first two years of growth in a commercial envi- ameters, canopy health, leaf nutrient content, yield ronment. Another objective was to decipher poten- efficiency, and fruit quality were assessed during the tial differences of root growth and root architecture production year 2018-19. Rootstock effect was found associated with propagation method and rootstock to be significant for most of the measured traits, cultivar. Multiple root and shoot growth parameters particularly tree vigor and productivity, in both loca- and the tree response to HLB were evaluated every tions. Differences were also found between the two six months after planting. Root growth was assessed locations, which may be due to different soil or en- bimonthly using minirhizotrons and a CI-600 in-si- vironmental conditions. The results from this study tu root imaging system. Results show that the tree suggest that the selection and use of superior root- performance was influenced more by the rootstock stocks may be key to enhancing citrus production in cultivars than by the method by which they were an HLB-endemic environment. propagated. The results from this study support the Specified Source(s) of Funding: CRDF potential for using rootstocks propagated by vege- tative methods in commercial citrus production sys- tems. 8:45 AM Micronutrient Uptake and Root Specified Source(s) of Funding: CRDF Growth and Development in HLB-Affected Grapefruit on Florida Flatwoods Soils Lukas Hallman*1; Rhuanito S. Ferrarezi1;