A coffee breeding program leaded by the University of Florida has potential to (i) leverage the research required to make the coffee industry more sustainable and (ii) support a local coffee production as an alternative crop for our growers and stakeholders. In this regard, this proposal will address the following specific questions: (i) can we grow coffee in the Florida region?; (ii) what genetic materials will be more adapted to our changing climatic conditions?; (iii) from the economic standpoint, what are the commercial and finance aspects related to coffee production as a new crop in Florida?; and (iv) how a modern breeding program can be established to guide future crosses and selections? Altogether, we anticipate that with modern breeding approaches, not only can we attend to farmer-focused traits, but that this project can move toward coffee selections for production in Florida, creating value for both farmers and consumers.

In 2020, Dr. Albrecht (UF/IFAS SWFREC) initiated a series of experiments using trunk injection to deliver oxytetracycline (OTC) to young and mature citrus trees and demonstrated significant reductions in fruit drop, significantly higher yields, and significantly better external and internal fruit quality. In October 2022, a 24(c) local special need label was approved that allows the use of trunk injection of OTC to manage HLB in Florida. The final clearance was given in January 2023. Despite the demonstrated positive effects associated with this technology, large-scale data of the benefits of OTC injections are still missing as are other details on best practices. The CRDF rootstock trials, established at SWFREC in 2015, provide an ideal opportunity to investigate, on a large-scale, the advantages or disadvantages of injection into the scion compared to injection into the rootstock while also examining differences among the different rootstock cultivars. These trials also provide an excellent opportunity to study fibrous root densities and if there are rootstock effects in response to the injection treatments.

Current citrus nutrient guidelines are based on studies of healthy citrus trees conducted in the pre-Huanglongbing (HLB) era and may no longer be valid for the present situation where 100% of the citrus trees in Florida are HLB-affected. We propose to conduct research on different N and P rates for young and mature citrus species including sweet oranges, grapefruits, and mandarins. Our project will evaluate 4 rates of N namely 100, 150, 200 and 250 lbs of N per acre and 4 rates of P at 7.5, 15, 30 and 60 lbs of P₂O₅ per acre. These rates will address the objective of evaluating different levels of N and P in identifying the appropriate site-specific rate of N and P for HLB-affected citrus using site soil characteristics and production practices to determine if we need to increase/decrease the current guidelines for N (200 lbs/acre) or P₂O₅ (15 lbs/acre). Using fertigation and controlled release fertilizer (CRF) fertilization sources, we should be able to develop and provide site specific N and P guidelines for young and mature citrus trees of sweet oranges in central and southwest Florida, grapefruits in the Indian River district, and Satsuma mandarins in the north Florida.

In this project we will collect soil and leaf samples of grapefruit and mandarin trees in a commercial grove, and analyze soil and foliar macro and micronutrient concentrations using a low-cost stand-alone bench nutrient analyzer (iMETOS MobiLab; Pessl Instruments GmbH, Weiz, Austria), standard soil and plant leaf tissue analysis (Waters Agricultural Laboratories Inc., Camilla, GA), and plant sap analysis (New Age Laboratories, South Haven, MI) in HLB-endemic region in the Indian River citrus District. The citrus groves used for this series of trials are in a farmer collaborator at the Indian River County in Vero Beach, FL.

Our goal is to improve fertilization efficiency by determining real-time nutrient status and calculate fertilizer needs. We will establish a relationship between analysis methods, and hopefully identify adequate ranges of nutrient sufficiency for the plant sap analysis to allow for modifications in the current fertilization strategies from 1 to 3 times per year to more frequent applications on demand to reduce the fertilizer input for commercial citrus production, providing nutrients in the right time and at the right rate and reducing the potential for nutrient runoff and leaching to water bodies and groundwater.

Despite reports of potential therapeutics for HLB control, limitations to commercialization include: low efficacy, cost of production, cumbersome/expensive methods of delivery; and daunting regulatory hurdles. This proposal builds on previous NIFA and ECDRE grant results of therapeutic molecule discover to: 1) establish an HLB-therapeutic molecule evaluation pipeline that leads to in-field evaluation and identification of the most cost-effective strategy to deliver these molecules to growers; 2) advance therapeutic strategies to field tests/commercial evaluation/regulatory approval. The focus is to rapidly move to whole plant performance and an economics-of-delivery evaluation (molecule + delivery method). A systems approach is presented involving expertise in diverse and complimentary disciplines, from synthetic and molecular biology to agricultural engineering, extension, agrichemical/biopesticide regulatory approval and commercialization. Field trials using three separate delivery methods will be conducted, including using two novel delivery methods invented and patented by our team. We propose a series of extension and education initiatives that involve land grant universities in multiple citrus growing states, Cornell University and Indian River State College in Florida. We are requesting Center of Excellence designation because our technology has the potential to transform rural agriculture, advances technologies for protein production beyond control of citrus greening to diseases in other crops, humans and other animals, coordinates activities across several national citrus greening research programs and will include community participation in evaluation of HLB therapeutics. This is an ambitious and aggressive proposal, but the scientists forming the team have strong track records and many represent international authorities in their areas of research.

The major goal of this project is to increase yield and quality of horticultural crop commodities by developing sustainable, environmentally sound, and effective management practices that improve and restore plant, root, and rhizosphere health. This project proposal aims to achieve this goal by:

• Developing new nutritional guidelines for HLB-affected citrus, with particular emphasis on grapefruit trees.
• Implementing cultural practices (e.g., oak mulch, cover crops, fabric mulch ground covers, etc.) that reduce agricultural inputs while increasing root and soil health.
• Studying and improving root system architecture of fruit tree rootstocks for different Florida soils (in collaboration with plant breeders).
• Identifying and quantifying the potential impact of abiotic stresses (salinity, heavy metals, and emerging pollutants) on rhizosphere dynamics, root physiology, and root anatomy.
• Assessing the viability and practicality of potential alternative crops for Florida’s agriculture producers (i.e., peach, pongamia, olive, coffee).

TERMINATED RESEARCH PROJECTS

• January 2020 – December 2021 A.H. Krezdorn Memorial Fund

  PI
  Curative effects of oak leaf extracts against HLB in Florida

  Currently, there is no cure for HLB, no compounds have been successful in controlling HLB, and no sustainable management practices have been established for the disease. Thus, searching for alternative citrus greening disease mitigation strategies is considered an urgent priority for a sustainable citrus industry. The aim of this study was to use compounds extracted from oak, Quercus spp., and to assess the antibacterial effects of these against CLas-infected citrus plants.

• January 2019 – December 2021 Citrus Research and Development Foundation

  CO-PI
  Development of root nutrient and fertilization guidelines for HLB-affected orange and grapefruit

  Root structure and function is an understudied component of citrus research in the age of Huanglongbing (HLB) disease. A better understanding of how roots are affected by HLB can potentially lead to better management options in the future. Fertilization guidelines utilize leaf nutrient concentrations to generate a fertilizer recommendation for N, P, K, Ca, Mg, and micronutrients. These guidelines were developed in pre-HLB times and may no longer be valid. There are currently no guidelines for optimal nutrient concentrations in healthy roots, and a disconnection in assessing how healthy trees are benefitting from current nutrient management strategies. Our objective is to conduct field trials using variable rate nutrient fertilization to determine optimal nutrient concentrations in leaves and roots, and relate these concentrations to indicators of tree health, growth, yield and fruit quality. Thus, we should be able to identify and quantify optimal nutrient concentrations in leaves and roots, and to determine if there is a relationship between them. By utilizing both fertigation, soil, and foliar fertilization treatments, we will be able to determine how different fertilization practices impact root nutrition, development and health, and how fertigation influences leaf nutrition and overall tree performance as well as fruit quality and sensory profile. Understanding linkages between root and leaf nutrients will allow for identification of the best fertilization application method and provide more insight on optimal rates of fertilization to improve the performance of HLB-affected trees.

• September 2020 – August 2022 UF/IFAS SEEDIT

  PONGAMIA: AN EMERGING ENTERPRISE FOR CITRUS GROWERS SEEKING AN ALTERNATIVE CROP

  Pongamia is a new enterprise gaining popularity in the Indian River region because it can be planted in previous citrus lands without additional infrastructure investment and is adaptable to the climatic conditions of the region. Pongamia pods can be used in many applications including biofuels and as a source of protein in animal feed. In order to promote Pongamia as a competitive alternative to citrus in Florida, adequate water-nutrient management strategies that promote healthy root systems and tree growth must be developed. Although the Pongamia industry claims the trees require minimum irrigation and nutrients, there is no evidence to support this claim. In this project, we propose the establishment of a Pongamia field trial at the Indian River Research and Education Center (IRREC). This trial will be the base for the development of Pongamia research and extension cooperative programs including water management, root biology, plant pathology, crop nutrition, and growers’ engagement. The data obtained from this field trial will be used to inform current and new Pongamia growers on the management practices required to maintain sustainable production. In addition, this trial will extend our understanding of Pongamia responses to the soil, water, climatic and biological stresses.

• September 2020 – August 2022 USDA SOUTHERN SARE GRADUATE STUDENT GRANT

  DEPLOYING OAK MULCH TO CONTAIN AND SUPPRESS HLB IN CITRUS

  Anecdotal reports from Florida growers have claimed that citrus growing within the drip line of large oak trees have minimal HLB symptoms, while citrus trees nearby but not under the oak tree drip line have severe symptoms. As a result, some growers are now using oak mulch in their citrus groves, and they noticed an overall increase in production. Following these observations, the main objectives of this study are (i) to study the capability of oak mulch to contain and suppress CLas, (ii) to measure the effect of oak mulch on HLB-affected citrus physiology, and root growth and development, and (iii) to study the effect of oak mulch on the rhizobiome. Soil, leaf and root samples will be collected monthly, along with root images. The products of this research will lead to the reduction of traditional treatments methods, while improving citrus industry sustainability and productivity and ensuring continued availability to the public of healthful citrus products.

• August 2019 – August 2022 USDA-APHIS-MAC

  CITRUS NUTRITIONAL THERAPIES FOR IMPROVING NUTRIENT ACCUMULATION, ROOT HEALTH, YIELD AND FRUIT QUALITY ON HLB-AFFECTED CITRUS

  Current UF/IFAS citrus nutrient recommendations are based on studies of healthy citrus trees conducted prior to the present situation with 100% HLB-affected trees (Obreza and Morgan, 2008). The goal of this study is to obtain information on selected rates of secondary macro- and micronutrients in conjunction with selected rates of N necessary to produce nutrient management recommendations on which citrus growers can rely.

• SEPTEMBER 2021 – JULY 2023 USDA NIFA

  FIELD STUDY TO EVALUATE THERAPEUTIC MOLECULES IN HLB-AFFECTED CITRUS

  PI: DR. LORENZO ROSSI (UF) PD: DR. ROBERT SHATTERS (USDA)

  This research will be evaluating plant physiological (stomatal conductance, photosynthesis, plant growth and development) and root biological (root growth and development, root HLB titer, root respiration) changes in citrus trees exposed to different therapeutic molecules in the field.

• SEPTEMBER 2018 – AUGUST 2023 USDA-HATCH-REEPORT

  PI

  ROOTING FOR THE FUTURE: OPTIMIZING ROOT AND RHIZOSPHERE DYNAMICS FOR SUSTAINABLE PRODUCTION SYSTEMS

  The long-term goal of this project is to improve sustainable agricultural practices, with emphasis on citrus, while improving and developing research tools to monitor plant root health and structure. The obtained results will facilitate the development of healthy agroecosystems, profitable agricultural production systems, and food security. Overall, there will be tangible benefits to the community and improve living standards locally, nationally and internationally. The main objectives of the project are: 

  • Determine optimal nutrient concentrations for multiple citrus varieties and rootstocks under HLB-endemic conditions to improve root health and increase tree productivity.
  • Develop new tools and approaches to characterize citrus root-system structure, architecture, and function in greenhouse and field trials.
  • Define the extent to which progression of HLB may involve changes in the relationship between the plant and the soil microbial community.
  • Identify and quantify the potential impact of emerging contaminants on rhizosphere ecology, root physiology and root anatomy.