Open to all ASHS graduate student members - the AHIS group is sponsoring a Lightning Talk Competition. In 5 minutes, use one PowerPoint slide to explain your research and one additional slide about how AHIS helps you and in return how you can be involved with AHIS. First place will receive $250! Second and third place will receive $150 and $100, respectively.
FFAR Fellows: Opportunities for Horticulture PhD Students - John Dole Nurturing Knowledge: The Impact of Assuming Professional Role in Achieving Learning Objectives in Upper-Level Horticulture Courses - Shivani Kathi Mid-semester Teaching Evaluations to Enhance Course Communication - Rebekah Maynard Evaluation of Packback - an AI-Assisted Writing Program for Student Assignments in Horticulture Courses - Navreet K Mahal Evolution Of An Undergraduate Tropical Crop Production Systems Course - Kent Kobayashi Service-learning Horticulture Students Growing Food for Themselves and Others - Carl Motsenbocker Assessing "Teaching Effort" to Ensure Fairness and Equity Across Diverse Course Types - Linda Prokopy
The Foundation for Food and Agriculture (FFAR) Fellows Program was launched in 2018 and has become the premier professional development program for food and agriculture doctoral students. The FFAR Fellows offers leadership and professional development training for PhD students studying food and agriculture-related sciences in the U.S. and Canada. North Carolina State University leads the initiative, which provides Fellows with training, networking opportunities, and peer support. The objectives of the program are to 1) develop leadership competencies that enhance current and future individual productivity and well-being, and enhance Fellows capacity to contribute to the public good, 2) connect young scientists across research domains and geographic areas to promote multi-disciplinary understanding and problem-solving, and 3) broaden students understanding of their career options and create links to sectors beyond academia (industry, government, NGO). Over a 3-year period members of each cohort (25-30 Fellows) attend four in-person meetings plus monthly virtual sessions, create and execute annual professional development plans, and network and establish mentor-mentee relationships with industry scientists and others outside of academia. Eligible students are those who have completed their MS degrees before the program starts or current PhD students with at least three years remaining in the program. FFAR provides 50% of the funds with the rest matched from industry, NGOs, commodity organizations, or other sources of non-federal funds. Deadlines are generally late February for the Stipend Professional Development Category (providing professional development $50,000/year in support) and mid April for the Professional Development Category (providing professional development). Application requirements will be discussed in the presentation. The research program of each Fellow must address one or more of the six FFAR challenge areas, five of which relate to horticulture: Soil Health, Sustainable Water Management, Next Generation Crops, Urban Food Systems, and Health-Agriculture Nexus. Approximately 7% of the 139 Fellows are from horticulture programs. There are opportunities for more horticulture PhD students to take advantage of this program.
Practical experience is invaluable to students majoring in plant-related fields including horticulture. Most times students with no prior practical experience acquire the required knowledge and skills to succeed in horticulture field through college education. However, there is limited literature on the impact of courses implementing experiential learning through students assuming horticulture-related professional roles on achieving learning objectives. Hence, the current study investigated the pedagogical approach of practical learning by incorporating students undertaking management role in achieving learning objectives of upper-level horticulture courses within a classroom setting. The methodology involves implementing this student-centered activity of assuming professional role as greenhouse manager and hydroponics operation manager in two different 3000-level courses (urban horticulture and hydroponics and soilless crop production, respectively) and assessing their impact on learning outcomes. Each student assumed the role of manager for a week and experienced real-world problem solving in greenhouse and hydroponics operation management settings. Quantitative and qualitative data collection methods, including surveys, and observational analysis, are utilized to evaluate the effectiveness of the approach in enhancing students' understanding and attainment of course objectives. Preliminary findings indicate that incorporating assumption of horticulture professional role activities fosters deeper engagement, critical thinking, and practical application of theoretical concepts. Students reported increased confidence in their abilities to apply learned principles in real-world scenarios, as well as a greater appreciation for the complexities of urban horticulture and hydroponics crop production. Overall, this research highlights the potential of experiential learning strategies, such as horticulture professional role simulations, to effectively support the achievement of learning objectives while providing students with valuable insights into professional practice. Finally, the findings contribute to the ongoing discourse on innovative pedagogical approaches and their impact on student learning outcomes in higher education settings.
Effective course communication is critical to foster a positive learning environment. One way communication can be improved is by scheduling a mid-semester teaching evaluation to capture student perspectives on what aspects of the course are going well and what could be improved. By providing students with a platform to express their opinions mid-semester, instructors have access to timely feedback to improve their teaching methods while the course is still ongoing. In this study, a mid-semester evaluation was conducted in an asynchronous, online Fruit Production course with 27 undergraduate students and one graduate student. The students were given a link to an online survey to respond to specific questions about the course structure and an open-ended question for actionable feedback. The evaluations were voluntary, anonymous, and confidential to solicit honest student responses. By having students respond individually, it was possible to capture unique student viewpoints and consensus statements among the class with a 96% response rate. Students responded positively to some aspects of the course such as the use of hands-on assignments; however, course modifications were made only in response to critiques. The most notable feedback was 14.8% of the students responding that the course material did not feel manageable with 44.4% of the class spending more than the expected time on lecture assignments. Additionally, students requested more clarity on the assigned projects. The survey responses were summarized for the students along with specific ways the course would be adjusted to better meet the student's needs and enhance their learning experience. To address the students’ concerns, the course workload was reduced, and students were provided with a clear explanation of their expected level of engagement. Recorded instructions along with detailed written descriptions and templates of the projects were also provided to aid in transparency about course assignments. Overall, students were well receptive of the mid-semester evaluation and reported it improved their satisfaction with the course. Because students found the mid-semester evaluation valuable to their learning, the course modifications will be maintained for future semesters.
The use of Artificial Intelligence (AI)-supported writing tools in higher education has been a hot topic since OpenAI introduced ChatGPT in 2022. These AI-supported writing tools are intended to analyze written materials and provide feedback on the writing , including grammar, vocabulary, content, and structure. Packback (https://www.packback.co/) is one of the AI-supported online platforms that intends to improve student curiosity, communication skills, and critical thinking, and provides ease of assessment for instructors. Two instructors in the Department of Horticultural Sciences at Texas A
TPSS 300 Tropical Production Systems is a four-credit undergraduate crop production course. It has two lectures and one lab period a week. In Spring 2023, there were 16 undergraduate students registered for this every Spring offered course—12 TAE students, one NREM student, one Interdisciplinary Studies student, one Botany student, and one Hawaiian student. In Spring 2024, there were nine undergraduate students—six TAE students, one Botany student, one Journalism student, and one Elementary Education & Special Education student. The objective is to describe the improvements made to TPSS 300 based on student interests and emerging new technologies and disciplines in horticulture. Various teaching techniques were used including flipped classroom, small group discussions, class discussions, in-class activities, lectures, guest speakers, field trips, YouTube videos, and laboratories. With a BYOD format, students could review assigned materials and look up information on the Internet to aid group discussions. New topics were added such as agricultural drone technology and crop sensors and equipment for monitoring plant status. Besides inviting our department graduate students as guest speakers, department extension agents and faculty and faculty and graduate students from other departments were invited. A TPSS faculty with another department’s faculty discussed the regulations for drone use and gave a demonstration of flying drones. The TPSS graduate students spoke on breadfruit tissue culture and industrial production in Hawaii; innovative agroforestry in ancient ways; and taro in aquaponics. Extension agents spoke about food safety. A PEPS graduate student spoke on invasive pests impacts on palm species with a focus on the Pacific and Israel. Two GEO students demonstrated their experimental growth chambers and artificial lighting set up. The manager of our college’s greenhouse facilities provided a tour of the facilities, explaining maintenance and irrigation. The rigor of this course was increased through incorporating more mathematics and quantitative reasoning, growth analysis, yield analysis, crop modeling and simulation, computer applications in horticulture, and high technology in horticulture. Students commented that TPSS 300 was a valuable learning experience. The course provided diverse learning experiences and hands-on activities. The integration of graduate students, extension agents, and the greenhouse manager as guest lecturers into the course worked well, providing benefits to both the speakers and the students.
Organic gardening (Horticulture 2525) is a mandatory class for students in the LSU medicinal plants and sustainable crop production concentrations, where the focus of the lab is for students to intensively grow their own garden plot of vegetables and herbs in the fall semester. Students are mandated to grow at least 10 different crops and to use both direct seeding and using their own transplants to establish, maintain throughout the semester, and then harvest their plot. The course is a service-learning course and over the years the class have worked in establishing and maintaining community and school gardens, harvesting/gleaning vegetables from garden plots, and assisting with a local farmers market. The most recent classes focused on growing food in community plots for the LSU Food Pantry, a local food bank that is used by many students. Each week students are required to work in the community rows from the beginning of working and shaping the beds, applying and incorporating fertilizer, planting seeds directly into the beds, transplanting crops, and setting up trickle and overhead irrigation systems. Students maintain their own plots as well as the community rows by fertilizing, and applying organic pest management measures as needed. The harvest from the individual plots and the produce is left up to the students and all the students harvest, wash, pack and prepare the product from the community rows for donation each week to the campus food pantry. Students are encouraged to participate my transporting the produce at least once, from the field or the cooler at the teaching facility to the food pantry. Many of the students have indicated that the class is the first time they had grown any plants in a garden and they used the garden harvest in their own kitchens. Students also indicated that they learned about the needs of the community and students and several also became aware of the food pantry and its services. In the fall of 2023 over 1,800 pounds of fresh vegetables were donated to the campus food pantry. Data from the students’ perceptions and comments from the semester will be presented.
Professor, Executive Director Louisiana Farm to School Program, Louisiana State University
Dr. Carl Motsenbocker is a professor of horticulture and sustainable agriculture at Louisiana State University. Motsenbocker is Executive Director of the Louisiana Farm to School Program and teaches Organic Gardening, Sustainable Agriculture and Vegetable Crops at LSU. Motsenbocker... Read More →
An ongoing and challenging issue for all administrators who have to assign teaching responsibilities is assessing “effort” associated with different types of courses. While it is abundantly clear that different amounts of effort go into lecture classes versus lab classes, we still frequently talk about teaching responsibilities as the “number of classes taught per semester.” In the department of Horticulture and Landscape Architecture at Purdue University, we faced this challenge across lecture courses, lab courses and Landscape Architecture studio classes. We undertook a year-long effort to assign “effort” values to each of our classes. In this presentation we will discuss our philosophy and approach to this undertaking, including how we engaged the entire department in the process. We ultimately developed a complex spreadsheet (currently being converted to an interactive database) that assigns points to classes based on number of contact hours, preparation work, service learning or experiential experience, grading/management workload, and class size. We then used this information to determine where additional support, in the form of graduate or undergraduate student TAs or staff, was most needed to create equity across teaching loads. This work is ongoing and needs to be updated annually based on changes in course structures and sizes and teaching assignments. In this presentation, we will share the database we created to make annual updates easy and transparent to everyone in the department.
Identification and Prevalence of Grapevine Virus Diseases (GVD) in North Carolina - Kimberly Heagy Learning Sustainable Edible Gardening through Hands-on Approach with Muscadine Grapes - Claude Judy Jean Creating a Practical Approach for Wine Grape Grower to Predict Grapevine Water Status by Precision Viticulture Technologies - Runze Yu Effect of Planting Distance on PD Resistant Predominantly Vitis Vinifera Grape ‘502-20’ During the Years of Establishment - Elina Coneva Genetics of Adventitious Root Formation in Dormant Bud Cuttings of Grapevines - Sadikshya Sharma Evaluation of Cordon Training System in Blackberry Production - Jayesh Samtani Enhancing the Fruit Set of NJ BP1-1 Beach Plum (Prunus maritima) - Rebecca Magorn
Grapevine virus diseases (GVD) are a leading cause of economic concern in the US grape and wine industry, including in North Carolina (NC). Visual vineyard observations in summer and fall of 2017 revealed GVD-like symptoms across European-style winegrowing regions in NC. These observations prompted a state-wide vineyard survey with two aims, (1) identify and assess the prevalence of common grapevine viruses in NC and (2) develop a GVD testing service for growers in NC. A vineyard survey was conducted after harvest (October
As the growing number of individuals moving to Florida has increased to over 1000 residents on average per day. Also, with the current focus on Florida’s water conservation
quality, alternative crops are a 15) and the second in March 2024 (n=19). Within both two-hour workshops, participants were able to go home with a muscadine grape cultivar of their choosing. The first workshop covered pest management, cultivar selection, and culture. Participants harvested and sampled fruit from different cultivars and then made cuttings of different varieties to propagate their own. The second workshop focused on the maintenance of grape vines. From the first workshop’s exit survey, participants reported intending on make changes to their landscape practices, including Right Plant Right Place (87%), Fertilize Appropriately (93%), Water Efficiently (67%), and Mulching (73%). 100% of participants also reported willingness to attempt to grow muscadines in the home landscape. From the second workshop, Right Plant Right Place (61%), Fertilize Appropriately (67%), Water Efficiently (44%), and Mulching (55%). 94% of participants self-reported that they felt better in managing muscadine vines, including installation
With the water regulations getting stricter in California and the climatic conditions getting warmer and drier during grape growing seasons, grape growers are forced to improve irrigation efficiency and eventually conserve water usage. This study was designed to incorporate soil moisture sensors and local above-ground weather stations to estimate grapevine water status with the goal to potentially replace pressure chamber measurement, which is the most popular plant-based method of measuring grapevine water status but labor-intensive and time-consuming. The study was conducted in a Barbera vineyard in Fresno, CA and there were four different regimes used in this study, including 50%, 75%, 100% crop evapotranspiration (ETc) replacement, and an over-irrigated condition (>150% ETc). Three Sony’s soil moisture sensors were installed at 20cm, 37.5 cm, and 75 cm in the soil paired with four time-domain reflectometry (TDR) sensors at 20cm, 37.5cm, 75cm, and 150cm in the soil to continuously monitor additional soil conditions besides soil moisture content. The above-ground weather conditions were collected from a nearby California Irrigation Management Information System (CIMIS) station (
Presently, Vitis vinifera grape production in Alabama and the southeastern U.S. is extremely limited due to Pierce’s disease (PD), caused by the bacterium Xylella fastidiosa (Xf) and vectored by insects from the family Cicadellidae. In 2019, UC Davis grape breeding program has released five PD resistant predominantly V. vinifera cultivars which can help sustain the vinifera grape cultivation in the region. Although these new cultivars are currently available, no V. vinifera grape production and management recommendations exist for Alabama conditions. An experimental vineyard was planted at the Chilton Research Extension Center, AL in 2017 to determine the effect of planting distance on vegetative growth and productivity of PD resistant, predominantly V. vinifera advanced selection ‘502-20’. The experiment utilizes a randomized complete block design consisting of three blocks with three vines per block. Vines were planted at an in-row distances of 1.8m, 2.1m and 2.4m and a between row distance of 3.7m and trained to a Watson system. Vine phenology, vegetative growth, yield, and fruit quality characteristics data were recorded during the period of vine establishment (2019-2023). Our results suggest there was a significant treatment by year interaction effect on pruning weight with the lowest pruning weight of 0.8 kg/vine found for vines at an in-row spacing of 2.1m during 2021. Treatment by year interaction also resulted in the highest yield per vine (28.0 kg/vine) measured for vines planted at 2.4m in 2021. Planting distance of 2.4m resulted in a significant increase of the number of clusters per vine during 2021 and 2022 seasons, while no vine spacing effect was found to account for differences in cluster weight, berry mass, or total soluble solids (TSS). Current results indicate planting distance of 2.4m x 3.7m can increase the yield of ‘502-20’ during the years of vine establishment and contribute to sustainable production of PD resistant predominantly V. vinifera grapes in Alabama conditions. Further research will be conducted to expand current knowledge and assist in the development of management recommendations for the successful production of V. vinifera grapes in the region.
Grapevine propagation depends on the formation of adventitious root formation. Vitis riparia and V. rupestris, two native species of North America, serve as the progenitors for the majority of commercially available rootstocks, especially due to their resistance to Phylloxera and ease of propagation. Despite the presence of at least 20 other native Vitis species in North America, many possessing strong resistances to biotic and abiotic stresses, their utilization has been limited by either poor rooting capabilities or insufficient understanding of their rooting potential. This study aims to achieve two main objectives. Firstly, to assess the rooting capabilities of 208 accessions across 20 different species through a dual approach combining traditional evaluation methods with AI-enhanced image analysis. Secondly, to pinpoint the genomic regions linked to rooting ability via a genome-wide association study, which will aid breeding efforts through marker-assisted selection. Preliminary analyses indicate that rooting capability is not solely species-dependent, as there is considerable variation in performance among accessions within the same species. Ultimately, this research will facilitate the development of new, better-adapted rootstocks, which will be crucial in the face of climate change and the increasing prevalence of biotic stresses.
I am a PhD candidate working on grape breeding and genomics at the University of California Davis. I am working on developing high-throughput phenotypic and genomic tools for salt and drought tolerance in grapes.
Tuesday September 24, 2024 1:10pm - 1:20pm HST
South Pacific 4
Commercial blackberry producers use various types of trellising systems to support the canes and prevent damage from wind and added fruit weight. The objective of this study was to determine the fruit yield and quality with a new training and pruning strategy (cordon system) in a T-trellis system. The 2022-23 growing season was the first year of a two-year study to evaluate the conventional winter pruning and training strategy against a modified “cordon” training system, with the Prime-Ark® Traveler cultivar, at the Hampton Roads AREC in Virginia Beach, VA. The study was set up as a completely randomized design with two treatments and six replicates. Each replicate had 3 plants. The conventional pruning and training strategy involved leaving 4 to 6 main canes along with their laterals per plant. The cordon system had 2 to 4 canes pruned to the height of each trellis wire allowing two laterals per cane to extend horizontally along the wire in both directions. The intent was to distribute the fruit weight along the wires, making harvest easier. New primocanes were trained to the wires in the same manner after spent floricanes are removed. All winter pruning was done between 10 and 20 March, 2023. Fertigation was done as per standard extension recommendations. Harvesting was done two to three times per week beginning 30 May and ending 28 August 2023. Fruit yield was collected by replicate and fruits were categorized as marketable Grade 1, Grade 2 or nonmarketable. The nonmarketable fruits were recorded as having white drupelet disorder, diseases, and insect or “other” damage. Fruit size, firmness, total soluble solids (TSS) and pH data were collected on ten Grade 1 berries per harvest week and data were averaged for the season. Statistical analysis was done with two-sample t-test at alpha =0.05. The conventional training and pruning strategy had an overall higher total, marketable and nonmarketable yield. Fruit size was slightly smaller in the cordon system and no differences in firmness, TSS or pH were observed.
Wild plum, Prunus maritima, has a native habitat that ranges from coastal Virginia to Nova Scotia and is well known to be associated with beach communities with sandy soils. Recent trials by Rutgers, New Jersey Agricultural Experiment Station suggests beach plum has the potential to be grown throughout the state where higher clay content, fertile soils contribute to increased vegetative growth leading to a dense bush habit. Crop potential is abundant due to high natural bloom density. However fruit set has been challenging under traditional commercial growing systems, partly due to self-incompatibility. BP1-1 Jersey Jems cultivar was bred and selected by the Rutgers University Plant Breeding program for its high yield, large size and superior flavor in costal locations where there are diverse beach plum pollen clouds. In order to establish clonal orchards of this cultivar, a pollen parent must be identified. In this study, a total of 7 controlled test crosses were made in triplicate on BP 1-1. Fruit yields were collected from BP1-1 and top yielding crosses were noted. The purpose of this study is to find compatible pollen parents, ensuring quality and uniform yield to base future pollen parent recommendations in New Jersey commercial tree fruit orchards.
Comparing Scion and Rootstock Trunk Injection of Oxytetracycline for HLB Management Across Diverse Rootstocks in Florida - Larissa Nunes da Silva Evaluation of Different Oxytetracycline Rates Delivery by Trunk Injections on Mature Valencia Sweet Orange Trees - Gabriel de Castro Marconi Pugina Field Performance of Novel Citrus Rootstocks Grafted with Valencia and Their Response to Systemic Delivery of Oxytetracycline - Caroline de Favari Tardivo Florida-grown 'Hamlin' Sweet Orange Failed to Produce Adequate Pounds-solids Despite Budline, Environment, and Antibiotic Treatment - John Chater Hedging, Thinning, Controlled Release Fertilizer, and Oxytetracycline Trunk Injections to Mitigate Fruit Disorder Incidence in HLB-Affected 'Sugar Belle' Mandarin - Joe Volpe Grove First: A Framework to Find Citrus Greening Treatments that are Safe, Affordable, and Available.- Guilherme Locatelli Can We Improve Growth and Production in HLB- Affected Citrus Trees Using Plant Growth Regulators? - Prudhvi Vulchi Methyl Salicylate and Gibberellic Acid For The Rehabilitation Of HLB- Affected Sweet Oranges. - Gurleen Kaur
The huanglongbing (HLB) associated pathogen Candidatus Liberibacter asiaticus (CLas) inhabits the phloem of infected citrus trees, which impedes the efficacy of foliar-applied chemicals for management of the disease. Trunk injection is an alternate method that allows the targeted delivery of agrochemicals into the vasculature, resulting in their systematic distribution throughout the tree. This study aims to determine the large-scale efficacy of trunk injection of oxytetracycline (OTC) on citrus tree health, fruit quality, and yield in existing rootstock trials in a commercial production site in Florida. The study compares 9-year-old Valencia sweet orange (Citrus sinensis) trees grafted on six different rootstocks in a large field trial in Polk County, Florida. The experimental design is a complete randomized block design, with three injection treatments: 1) no injection (control), 2) injection into the scion trunk, and 3) injection into the rootstock trunk. The injections were performed in May 2023, and injected trees received a commercial formulation of OTC at a rate of 1.1 g per tree using FlexInject injectors. Data collection included HLB status, tree size, yield, fruit/juice quality, fibrous root density, and leaf macro- and micronutrient content once a year, wound phenotype every six months, and bacterial titers before injection and 3 days, 1 week, and 1 month after injection. OTC injections into the scion or the rootstock trunk improved tree health, yield, fruit/juice quality, and the leaf Ca content. Overall, injections increased fruit yield by 24% and juice brix by 9%, increasing the revenue by 36% on a per acre basis. Injection into the scion trunk was slightly superior in terms of tree growth and fibrous root density, while injection into the rootstock trunk reduced the wound size, bark cracking, and HLB symptoms. CLas titers were reduced regardless of the injection site one month after injections. In conclusion, our results suggest that OTC injections have the potential for short-term management of HLB to help with the recovery of the Florida citrus industry in the face of endemic disease conditions. The trial will continue to assess longer-term effects.
In Florida, Huanglongbing (HLB), also known as citrus greening, has severely impacted citrus production, prompting research into alternative treatment methods such as trunk injection of oxytetracycline (OTC) to manage Candidatus Liberibacter asiaticus (CLas) colonization. This study aims to 1) determine the optimal OTC rate administered by injection to improve the health and productivity of HLB-affected mature sweet orange trees and 2) determine the impact of spring versus late summer injections to maximize benefits and the potential for extending the harvest window. The study was initiated in 2023 in a commercial citrus production setting in Polk County, Florida. The trees were 18 years old and composed of ‘Valencia’ (Citrus sinensis) scion on Swingle (C. paradisi × Poncirus trifoliata) rootstock. Four different OTC rates (0.55 g, 0.852 g, 1.1 g, and 1.65 g active ingredient per tree) and two injection times (June and September) were compared against a control receiving no injections. The experimental design was a randomized block design with eight replications, and each replication consisted of four linear trees. A commercial formulation of OTC registered in Florida was used and administered through FlexInject injectors. A volume of 100 ml per tree was used for the 0.55-1.1 g rates and administered with one injector. The highest rate (1.65) was administered using two injectors on opposite sides of the tree in a volume of 75 ml per injector. Tree health was assessed by visual ratings of foliar HLB symptoms and canopy densities, while CLas titers were quantified using real-time PCR. Fruit quality and yield measurements included total soluble solids, titratable acidity, fruit weight, and juice characteristics. Trees were harvested, and fruit/juice quality was determined in March 2024. Overall, injected trees produced significantly more and larger fruit with better juice color, a higher percentage of juice, and more total soluble solids than control trees. The highest rate of OTC produced the highest yield and highest-quality fruits compared to the other rates. We did not observe any difference between spring (June) and summer (September) injections on any measured variables. Bacterial titers were reduced in the injected trees compared to the non-injected trees, and injected trees had fewer HLB symptoms and denser canopies than control trees. This research provides important insights into the best practices for managing HLB using trunk injection of OTC.
Worldwide citrus production faces significant challenges from the devastating disease Huanglongbing (HLB), necessitating innovative management strategies. This study aimed to assess the performance of novel rootstocks under natural HLB-endemic conditions using regular management practices and the recently registered practice of delivering oxytetracycline (OTC) through trunk injection to reduce pathogen load. Nine novel rootstocks, US-1673, US-1676, US-1680, US-1672, US-1687, US-1688, US-2111, US-2132, and US-2137 with different genetic backgrounds, including Citrus maxima, C. tachibana, C. reticulata, and Poncirus trifoliata were included in the study. Also included were two commercial rootstock standards, sour orange (C. aurantium) and Swingle (C. paradisi × P. trifoliata). The rootstocks were grafted with ‘Valencia’ sweet orange (C. sinensis) scion and planted in 2014 in a randomized complete block design and 12 single-tree replications in an open field in St. Lucie County, Florida. In July 2023, half of the trees were injected with ReMedium TI® (95.0% oxytetracycline hydrochloride) dissolved in reverse osmosis water acidified with muriatic acid to a pH of 2.0. Each tree received 0.75 g OTC dissolved in a volume of 75 ml (10,000 ppm) administered using FlexInject injectors. Injections were performed in the scion, approximately 5 cm above the graft union. Tree measurements included tree size, canopy health, pathogen titers, fruit yield, and juice quality. Significant differences among rootstocks were observed in the years before injection. In the 2022-2023 production season, US-1688 induced the highest yield, and US-2132 induced the best juice quality. Preliminary results indicate an overall positive response to the OTC treatment across all rootstocks. Injected trees had a 36% increase in yield, an 11% increase in juice brix, and a significant reduction in leaf and root pathogen titers. As in the previous years, growth and productivity varied significantly among the rootstock cultivars. US-1688, a new release by USDA under the name SuperSour 4, continued to be among the largest, healthiest, and most productive trees. The results from this research demonstrate the importance of rootstock selection for sustainable citrus cultivation. It also highlights the benefits of integrating the systemic delivery of antibacterial therapies to maximize the resilience of citrus trees to HLB.
Huanglongbing (HLB) is a devastating bacterial disease in Florida and has been spreading in citrus-growing regions in Texas, Georgia, and California. HLB threatens the entire US fresh and processed citrus industries. To date, all commercial sweet orange (Citrus sinensis L. Osbeck) cultivars are susceptible, though some are more tolerant than others. The citrus industry has an estimated economic impact nationwide of over $13 billion. The currently applied strategies for mitigating this disease are costly and unsustainable. The development and commercialization of HLB tolerant sweet orange scions is needed for sustainable and profitable citriculture in the US. Citrus Under Protected Screen (CUPS) is a method used in Florida to exclude the Asian Citrus Psyllid (Diaphorina citri Kuwayama, or ACP), which is a phloem-feeding hemipteran insect that is the vector for Candidatus Liberibacter asiaticus CLas the causal agent believed to be responsible for HLB disease in citrus. ‘Hamlin’ sweet orange is the most important early sweet orange for processing in modern history. ‘Hamlin’ has a budline called ‘Hamlin 1-4-1’, which is the predominant budline in the State of Florida. ‘Hamlin 1-4-1’ has high susceptibility to HLB, which causes symptoms such as blotchy mottle, small fruit size, high titratable acidity (TA), low total soluble solids (TSS), and severe fruit drop. ‘Hamlin N13-32’ is a new budline of ‘Hamlin’ sweet orange that appears to have enhanced tolerance to HLB in terms of tree health. ‘Hamlin 1-4-1’ and ‘Hamlin N13-32’ trees were followed for two years in multiple environments with and without treatments of oxytetracycline. Tree size, rootstock, fruit number, fruit size, TSS, TA, TSS:TA ratio, and pounds-solids data were collected to determine the effects of environment (CUPS versus outside grove), antibiotic treatment effects, and budline effects on production. There were some significant differences among groups for fruit quality, but more research is needed to determine effects of oxytetracycline, budline, rootstock and environment on ‘Hamlin’ sweet orange production.
Global citrus production has been severely impacted by huanglongbing (HLB), a disease presumably caused by the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas). While there are not any commercial citrus cultivars currently available that have total resistance to this pathogen, several varieties show some degree of tolerance, including the LB8-9 ‘Sugar Belle’ mandarin. This cultivar was released by the UF/IFAS CREC Plant Improvement Team in 2009 and is known to be one of the most HLB tolerant varieties in HLB-endemic conditions when considering tree health. Fruit from this cultivar can be used for juicing or in the fresh market and with proper cultural care the trees consistently produce relatively high yields with typically an acceptable ratio of total soluble solids (TSS) to titratable acidity and value in pounds-solids per acre. Despite the improved tolerance to HLB in ‘Sugar Belle,’ many growers in Central and South Florida have had increased incidences of fruit disorders with this variety in the past several seasons. Fruit that are misshapen, have a poor peel color, or go soft on the tree are more common making this cultivar often undesirable for packing houses. The objective of this study is to determine if hedging the trees at different times (early summer, middle summer, or late summer), manually removing ~50% of the developing fruit in July (thinning), controlled release fertilizer applications, or oxytetracycline trunk injections will help mitigate some of the incidences of fruit disorders and increase overall fruit and juice quality at harvest. There were two sites used for this experiment (The Citrus Research and Education Center in Lake Alfred, FL, and Tamiami Citrus “Bee Branch Grove” in Avon Park, FL) and it was conducted over two seasons 2022-2024. Significant differences (p-value < 0.05) were discovered among the treatment groups in terms of TSS, titratable acidity, sugar:-acid ratio, pounds-solids per box, fruit size, yield, percent asymptomatic fruit, and peel rupture force. Despite evidence that some treatments may provide benefits to the grower, more research is needed to mitigate the soft fruit problem in ‘Sugar Belle’ mandarin.
Citrus greening (Huanglongbing, HLB) is considered one of the most devastating diseases affecting the global citrus industry. There is an urgent need to provide relief from HLB and restore profitable citrus production. Since 2005, over a billion dollars has been spent on research to find a solution to HLB. Trunk injection with the antibiotic oxytetracycline is the current treatment that Florida growers are using to manage the disease. To broaden the number of molecules available to growers to treat HLB a framework was developed to efficiently screen molecules in citrus groves, selecting those that enhance tree health over a season. The framework is based on the principles of the design-of-experiments (DOE). Utilizing the injection system developed by TJ Biotech (LLC), 88 molecules were injected into 8-year-old ‘Valencia’ sweet orange (Citrus × sinensis) trees grafted on ‘US-812’ (Citrus reticulata × Poncirus trifoliata) rootstock over a six-week period. The injections were divided into nine sets, with varying numbers of molecules injected in each set (12, 10, or 6). The injections were administered into the scion, approximately 5 cm above the graft union. Visual assessments of tree health index and canopy density were collected to evaluate changes in restoring tree horticultural traits. Ratings were recorded before injections and at 90 and180 days post-injections. In addition to health index and canopy density, a series of seven pictures were taken per tree on the injection day and subsequently at 30, 60, 90, and 180 days after injections. Pre-harvest fruit drops were measured by counting and removing any fruits on the ground beneath each tree. The total number of fruits on each tree was tallied at harvest to calculate the percentage of fruit drops for each tree. Yield, fruit, and juice quality were assessed at harvest. In this screening trial, trees injected with oxytetracycline have been used as a positive control to indicate enhancement in tree health. Results from the tree health index obtained at 90 and 180 days after injection showed that 17 molecules performed similarly or better than the oxytetracycline-treated positive control. We are partnering with regulatory consultants to identify those that are safe and affordable. New molecules for injection will require regulatory labeling.
Emerging Pests and Pathogens Research Unit, USDA Agricultural Research Service/ Plant Pathology and Plant Microbe Interactions Section, School of Integrative Plant Science, Cornell University
Huanglongbing (HLB) disease is arguably the biggest concern for citrus growers in Florida causing a drastic more than 75% decline in citrus-bearing acreage since 2005. HLB symptoms include sparse canopy, poor leaf growth and development, ultimately resulting in yield losses. Standalone applications of plant growth regulators (PGRs) and certain antibiotics have been reported to reduce the impact of HLB on tree growth and promote new flush growth. However, very little research has been done on synergistic effect of PGRs and antibiotics on tree growth and yield. The goal of HLB mitigation strategies is to promote a denser canopy, enhancing source to sink ratio as trees with dense canopies are known to produce high fruit yield. Thus, we initiated a field study to evaluate foliar applications of PGRs (auxins, cytokinins, and gibberellins) and trunk injections of Oxytetracycline (OTC) in 9-year-old orchards of Valencia on ‘Swingle’ rootstock in central Florida. This is the first research in citrus where PGRs are being applied according to tree phenology. The experimental design is a split-plot with a completely randomized block design with 8 replications. The antibiotic programs (with and without OTC injections) are assigned to the main plots, while the PGR treatments assigned to the subplots consist of an no PGR control, PGR applications with varying concentrations, and PGR applications with constant concentrations throughout the year. Parameters such as leaf area, fresh weight, dry weight, water content, chlorophyll content, starch content and carbohydrate content from leaf samples are recorded every three months starting from July 2023. Over 9 months no consistent pattern of PGR or OTC treatment was observed for vegetative traits. Nonetheless, Non-OTC trees showed higher leaf water content compared to OTC during the dry season months of October and January. Regarding yield, the study suggests that both PGR treatments, when applied with or without OTC lead to significant improvement in yield. PGR variable treatment showed 30% improvement in yield efficiency compared to both the control and PGR Constant treatments. No difference is observed between OTC and Non-OTC programs in terms of yield efficiency. These findings suggest that use of PGR treatments regardless of use of antibiotics can be beneficial for growers.
Investigating the Effect of Pecan Rootstock on Rhizosphere Soil and Root Microbial Communities - Xinwang Wang Enhancing Urban Food Production: A Multi-Omics Investigation of Microbe-Mediated Soil Improvement and Plant Nutrition in New York City Farms - Yejin Son The Effect of Reclaimed Water on Young Blueberry Seedling Root Architecture Using Rhizotron Technique - Yasmeen Saleem Root Characterization Analysis of Navajo Peach Seedlings - Reagan Wytsalucy Characterizing Root Dynamics and Phenology of Hops in a Subtropical Climate Using an In-situ Root Imaging System - Alvaro J. Bautista Effects of Reclaimed Water on Blueberry Seedling Growth and Root Morphology - Yasmeen Saleem
Pecans (Carya illinoinensis), the most valuable native North American nut crop, are commonly propagated through grafting to maintain desired traits from parent trees. Successful pecan cultivation relies on scion varieties, rootstocks, and soil conditions. This study investigated the microbial abundance and diversity in soils and roots of a southern rootstock (87MX5-1.7) and a northern provenance ('Peruque') in a rootstock test orchard, both grafted with a 'Pawnee' scion cultivar in the USDA ARS Pecan Breeding program. The 16S ribosomal RNA of bacteria and ITS of fungi were sequenced and annotated into trophic and nutrient-related groups to characterize the rhizosphere microbiota. The results showed fungal dominance over bacteria, with Peruque roots having a higher relative abundance of saprotroph fungi compared to 87MX5-1.7, while 87MX5-1.7 exhibited higher levels of nitrogen fixation-related bacteria. Despite no significant difference in diversity index, the presence of symbiotrophs, especially the ectomycorrhizal fungi, exhibited distinct ectomycorrhizal fungi, which may lead to a divergent pathway of nutrient translocation between these two rootstocks. The study suggests rootstocks from different origins shape rhizosphere microbiota differently, affecting nutrient uptake and potentially nut yield. Exploring rootstock-fungi combinations could enhance grafting success and ultimately increase nut yield.
Urban agriculture (UA) is an emerging food production system in which farmers grow crops within cities. However, many urban farmers face challenges with their compost soils, including poor soil structure and low nutrient availability. This study aimed to utilize beneficial microbes, such as arbuscular mycorrhizal fungi (AMF) and phosphorus solubilizing bacteria (PSB), to address soil aggregation and biological phosphorus (P) cycling in UA soils while also assisting urban farmers in generating higher economic returns. We cultivated Bush Champion II Hybrid Tomatoes (an indeterminate tomato cultivar) in three organic urban farms in New York City in 2022 under four different treatments: 1) Control tomatoes, which were not treated with PSB or AMF; 2) Tomatoes treated with PSB; 3) Tomatoes treated with AMF; and 4) tomatoes treated with PSB and AMF. Our hypothesis posited that the positive interactions of PSB and AMF would synergistically enhance soil phosphorus cycling and carbon accumulation and, thereby, promote plant growth and nutrition. Our findings indicate that the combined application of AMF and PSB increased the overall abundance of soil microbiomes, as measured by flow cytometry. There was also an increase in the production of soil-aggregating proteins and soil acid phosphatase activity. Additionally, the nutrient uptake by tomatoes, including calcium (Ca), potassium (K), and phosphorus (P), was enhanced. We also employed omics approaches using deep sequencing metagenomics and metaproteomics to generate meaningful insights into how AMF and PSB interacted with soil native microbial populations and defined soil microbiome functions. Our findings offer novel insights into the characteristics and functions of soil microbiomes in UA soils. This knowledge will contribute to advancing the potential of beneficial microbes in enhancing food production within urban agriculture systems.
Southwest Native American Tribes, such as the Navajo, Hopi, and Pueblo, have grown peaches at least since the early 1600’s, making them a nutritionally and culturally important food source. Historic management practices consisted of reduced irregular irrigation of sandy to sandy loam soils with no fertilizer additions, no pruning, and no fruit thinning. Recent research indicates germinated peach seedlings from seed sourced from a Navajo orchard in Utah are more drought resistant when compared to direct seeded ‘Lovell’ seedlings, and container transplanted ‘Lovell’ seedlings. The purpose of this study was to characterize the Navajo seedlings’ root distribution after direct seeding to better understand their rooting dynamics with regular irrigation and no pruning. All trees were direct seeded in May 2018 and destructively sampled in May 2022. Three trees from each Navajo and ‘Lovell’ treatment were destructively harvested to determine above ground biomass. Root distribution (location relative to the trunk and depth in the soil profile) was determined using a soil core sampling technique. Soil cores were taken in a radial array around the tree, and tree roots (small, medium, large) were separated from the soil cores in the field, before drying and weighing. After the cores were extracted, the remaining root system was excavated, air dried for 10 days, then weighed and photographed. The main effect and interactions of tree type, sampling location, and depth were tested by analysis of variance. The Navajo seedlings had a more extensive root system, including more roots in the grass alleyways, than Lovell seedlings indicating a more competitive root system. There were also qualitative differences in root types between Navajo and ‘Lovell’ in the occurrence of lateral primary roots, sinker roots or fibrous roots. The results of this research will be utilized to determine the Navajo seedlings’ potential for becoming a viable rootstock for the fruit industry.
In Florida's subtropical climate, photoperiod manipulation facilitates a unique production system for hops (Humulus lupulus L.), an important crop for the brewing industry, with two growth cycles per year. The spring season spans from mid-February to early June, immediately followed by the fall season, which concludes in late November. With contrasting climatic conditions, plant phenology, yield, and cone quality differ dramatically between the two growing seasons. To gain insights into the roles of roots in the seasonal differences in plant phenology and performance, we characterized root dynamics and phenology of 'Cascade' hops grown in West Central Florida using an in-situ root imaging system. The soil at the study site was Myakka fine sand with 97% sand. Plants were grown on a 4.5 m V-trellis system, and data were collected over 2 years upon transplanting. Minirhizotron tubes were installed at varying distances (0, 30, and 60 cm) from the planting hill perpendicularly to the row to capture biweekly root images up to a depth of 84 cm. These images were processed using WinRhizo Tron software to measure various root morphological parameters, including total root length, projected area, surface area, volume, and the longest root. Notably, hop roots showed rapid elongation, reaching a depth of 84 cm, and expanding up to 60 cm from the hill center within one month after establishment under subtropical conditions. However, the primary, larger in diameter tap roots exhibited signs of decay after 5 months, culminating in complete mortality within 15 months following their establishment. Interestingly, the phenological stage of cone development induces a proliferation of new root growth, although temporary, with these ephemeral roots having a lifespan limited to approximately 3 months. These results can provide insights into the shoot-root interactions and help improve fertilizer, water, and ground cover recommendations, ultimately optimizing hop production in Florida's unique subtropical system.
A high percentage of agricultural production depends highly on groundwater irrigation. Groundwater depletion has been putting significant pressure on global water resources and food production. Using reclaimed water (RW) as an alternative source of irrigation water for crop production can mitigate the huge demand on groundwater resources. Blueberry plants are characterized by their preference for acidic soil conditions with a shallow, salt-sensitive root system. The alkaline and saline nature of RW necessitates an understanding of its suitability as irrigation water for blueberry production. We conducted a greenhouse rhizotron experiment to characterize root morphological responses of ‘Arcadia’ blueberry seedlings to RW. Four irrigation water treatments were implemented: 100% well water (WW), 100% deionized water (DW), a blend of 50% DW/50% RW, and 100% RW. These treatments were applied to rhizotron boxes filled with 50% sand and 50% pine bark mixed uniformly by volume. Root morphological variables, stem diameter, plant height, canopy projected area, and plant physiological variables were examined biweekly. Soil and plant tissue nutrient contents and plant biomass were examined at the end of the experiment. Water quality was slightly alkaline with pH values of 7.8 for 100% WW and 100% DW, and 7.7 for 100% RW. Electrical Conductivity (EC) values varied among the treatments, with 0.428 dS/m for 100% WW, 0.338 dS/m for 100% DW, and 0.769 dS/m for 100% RW. Initial soil mix pH at the beginning of the experiment was 6.8. Our preliminary findings indicate no significant difference in root elongation, plant above-ground biomass and leaf chlorophyll index among the four irrigation treatments (p > 0.05). A significant difference was observed between DW and WW for plant stem diameter and height (p > 0.05), possibly attributed to blueberry plants’ sensitivity to salt. The soil mix pH had risen to 7.8 for all the treatments at the end of the experiment. Our preliminary interpretation suggests that 100% RW does not adversely affect young blueberry plants growth parameter over the short-time period of the experiment. That indicates that RW can be a promising alternative of irrigation. Existing literature indicates that blueberry plants have the ability to adopt to irrigation water EC level of up to 2 dS/m, while the measured EC of 100% RW was 0.77 dS/m, it appears that the blueberry plants didn’t reach to the stress level that could significantly affect their growth parameters. We believe the experiment duration was insufficient to observe the high pH symptoms.
