Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 102 - Soil, Plant, Water, Nutrient Relationships | 999 - Citrus, general/other | 1020 - Physiology | 50% |
| 205 - Plant Management Systems | 999 - Citrus, general/other | 1010 - Nutrition and metabolism | 40% |
| 102 - Soil, Plant, Water, Nutrient Relationships | 110 - Soil | 1070 - Ecology | 10% |
The citrus industry is struggling for survival due to the presence of Huanglongbing (HLB), a.k.a citrus greening. The suspected causal organism of HLB is transmitted to the plant by a sap-feeding insect, the Asian citrus psyllid. Hence, management strategies to retain productivity involve use of large amounts of insecticides. HLB also results in nutritional deficiencies and root decline which has resulted in frequent applications of nutritional formulations in order to alleviate disease symptoms and retain productivity. More recently, the use of antibiotics was approved in the hope to prevent tree decline and induce recovery of affected trees. But despite all these efforts, citrus production continues to decline and more sustainable and environmentally friendly strategies are needed to cope with the negative effects of the disease. Commercially grown citrus trees are composed of an above-ground part, the scion, and a below-ground portion, the rootstock. Rootstock selection is an important part of commercial citrus production and can determine success or failure of a citrus operation. Besides influencing tree size, fruit size, and fruit quality, rootstock can also impart tolerance to pests and diseases and to different environmental stresses. Several rootstock varieties were shown to be tolerant to HLB. Therefore, rootstock provides a sustainable strategy to combat HLB and enhance productivity. Since there is a high demand for superior rootstock varieties, alternative propagation methods are being employed, but little is known on how these methods affect tree performance under commercial conditions. Root health can be improved through use of soil amendments in the form of beneficial soil bacteria or fungi and organic substances such as humic or fulvic acids. These substances have been shown to improve root architecture as well as water and nutrient uptake and use efficiency. In addition, they were shown to activate plant defense response, rendering the plant more resistant to different stresses and diseases. Use of these products in combination with the right choice of rootstock provides a much more sustainable alternative to currently implemented management strategies. However, not much is known about the specific effects and connections between rootstocks, propagation method and different types of amendments. This research will provide much needed information and is expected to generate more sustainable strategies that will aid in coping with the detrimental effects of HLB.
Little is known about the effects of different organic amendments and other substances that are part of the large category of biostimulants on citrus growth and tolerance to different biotic and abiotic stresses and their interaction with rootstock types propagated via conventional methods or other horticultural methods. The goal of this research is dedicated to shed light on these effects and the underlying physiological mechanisms, especially as they relate to HLB, and provide citrus growers with alternative tools to enhance citrus production in a more sustainable manner. Specific objectives are as follows:
Objective 1. Conduct greenhouse experiments to assess efficacy of different biotic and abiotic amendments. Greenhouse assays will be conducted on young citrus plants grown from seed and/or obtained from commercial citrus nurseries and methods will be explored that allow the efficient screening of different amendments and their possible interactions with rootstock type. Pilot studies have been initiated at the SWFREC. Experimental methods will include root system measurements, root metabolic activity, and other plant physiology or molecular biology methods, as well as analyses of the root/soil microbial community using metagenomics and bioinformatics procedures in collaboration with a soil microbiologist located at SWFREC. Experiments will be conducted in greenhouses located at SWFREC and/or at greenhouses located at collaborator institutions.Objective 2. Establish field trials in commercial citrus groves and/or at the Southwest Florida Research and Education Center (SWFREC) farm site in collaboration with commercial citrus growers and citrus breeders (UF and USDA), or use existing field trials at different locations throughout Florida to assess effects of different rootstocks, differently propagated rootstocks, different biotic and abiotic amendments, or other alternative management strategies on tree growth and performance as well as resistance to diseases and environmental stresses. Several field trials in commercial settings and the SWFREC have already been established. Assessment of tree performance will include different metrics such as root health, fibrous root mass, tree height, canopy volume, trunk diameter, fruit production, and quantitative tree ratings to assess disease intensity and impacts. Plant tissue samples such as fibrous roots and leaves will be collected at different time intervals and proteins, enzymes, DNA, RNA and other compounds will be extracted. Various plant physiology and plant molecular biological procedures will be employed to elucidate the underlying mechanisms associated with differential performances as well as to determine disease status and progression. Methods will include root metabolic activity assays, spectrophotometric analyses of stress-related enzymes and expression analysis of genes associated with plant defense, stress and other physiological mechanisms via quantitative real-time PCR. Additional analyses will include the assessment of root/soil microbial communities as outlined above.
Target Audience
The target audience were primarily citrus growers and other industry stakeholders, including grove owners, grove managers, farm operators, etc.,as well as researchers, extension specialists, students, and the general public. Efforts provided were science-based information in form of in-person and virtualseminars/presentations, lectures, fact sheets,posters,online access to presentations, personal communications with stake holders, field visits, scientific journal articles, trade journal articles, and EDIS publications.
Changes / Problems
Because ofevidence for the lack of efficay of originally pursued citrus production strategies, priorities of research activities were redirected to focus on other citrus production strategies with more promise and relevance to the industry. Some research activities,travel, and in-person interactionswere compromisedand/or delayed because of Covid-19 relatedrestrictions and other complications.
Training & Professional Development
Opportunities for students and student interns were provided to assist with and/or leadresearch activities and present research data in form of conference presentations, student competitions, and posters. Students also assisted with or took lead preparingfact sheets, trade journal articles, and journal publications. In-person and virtual demonstrations and workshops were provided to the public to inform about program and ongoing research. Conferences and seminars/workshops were attended (in-person and virtual)to network, exchange research experiences, and acquire new knowledge.
Dissemination Streams
Research results have been presented regularly, either in-person or virtually, at local, regional, and national events (Research and Education Center presentations, Citrus Expo, Citrus Show, etc.). Findingswere regularly discussed with growers and other industry members through zoom meetings, in-person group meetings, phone conversations, text messaging, emails, or private visits/consultations. Dissemination of results also occured through seminar recordings, podcasts, and trade journal articles.
Next Reporting Steps
Nothing Reported
Target Audience
Target audience: The target audience are primarily citrus growers, nursery mangers, and other industry stakeholders, including grove owners, grove mangers, farm operators, etc.as well as other researchers, extension personnel, students, and the general public. Efforts: Provided science-based information in form of seminars/presentations (live and virtual), lectures, live demonstrations, information handouts/printouts,posters, online access to presentations, personal communications with stakeholders, scientific journal articles, trade journal articles, and EDIS publications.
Changes / Problems
The focus of the research has shifted away from biostimulants due to their lack of efficacy, especially in a commercial field environment.
Training & Professional Development
Opportunities for students and student interns were provided to learn about and assist with research activities. Laboratoy demonstrations and workshopswere provided.to the public to inform about program and ongoing research. Conferences and seminars/workshops were attended (mainly virtual due to Covid-19) to exchange research experiences and acquirenew knowledge.
Dissemination Streams
Research results were presented at local, regional, and national events (Research and Education Centerpresentations,Citrus Expo, Citrus Show, etc.), which were predomminatly virtual because of the pandemic.Findings were regularly discussed with growers and other industry members through virtual meetings,phone conversations, and emails. Other information was provided through recordings and trade journalarticles.
Next Reporting Steps
Continue with existing field evaluations and continue to present knowledge tostakeholders and provide learning experiences to students and the general public. Continue to disseminate research findings viapeer-reviewed publications. .. <br><br>
<br>What was accomplished under these goals? Objective 1: No new greenhouse studies were establishedto evaluate differentbiostimulant products as they showed no significantefficacy.New greenhouse studies were initiated to study alternative HLB management practices including the systemic delivery of therapeutic compounds. Objective 2: Horticultural data collection (tree size, fruit quality, yield, disease tolerance, etc.) on large-acreage field trials was continuedto assess treatments (organic amendments and rootstock cultivars) and plant performance under HLB-endemic conditions. New greenhouse and field experiments to study alternative HLB management options were initiated.Data were presented to stake holders through different venues (local and regional presentations, personalcommunications, EDIS publications, trade journal and peer-reviewed articles. <br><br><b>Publications</b><br>
Target Audience
Target audience:The target audience are primarily citrus growers and other industry stakeholders, including grove owners, grove mangers, farm operators, etc.) as well as other researchers, extension personnel, students, and the general public. Efforts: Provided science-based information in form of seminars/presentations, lectures, information handouts/printouts, posters, online access to presentations, personal communications with stake holders, scientific journal articles, trade journal articles, and EDIS publications.
Changes / Problems
Due to the observed low efficacy of the biotic and abiotic amendmends tested in a commercial citrus production environment, future research will focus more on rootstock selection and other HLB management strategies.
Training & Professional Development
Opportunities for students and student interns were provided to learn about and assist with research activities. Lab demonstrations to the public about program research activities were provided. Attended conferences to exchange research experiences and gain new knowledge.
Dissemination Streams
Research findings were presented at local, regional, and national events (Research and Education Center presentations, Citrus Expo, Citrus Show, etc.). Findings were also discussed with growers and other industry members during personal meetings, phone calls, and emails. Further information was provided in form ofEDIS publications andtrade journal articles.
Next Reporting Steps
Continue with existing field evaluations and establish new field trials on a larger scale. Continue to present knowledge to stakeholders and provide learning experiences to students and the general public. <br><br>
<br>What was accomplished under these goals? Objective 1: Greenhouse studies were replaced with field studies. Horticultural data collection (tree size, canopy density, foliar disese symptoms, yield, etc.) was conducted to assess plant responses to treatments and performance of different citrus rootstock varieties. Unfortunately, biotic and abiotic amendmends did not show any measurable positive effect on tree growth and productivity. A new multiple-year project was inititated to study the interaction of soil amendments and rootstock cultivar on a larger scale. Data were regularly presented to stake holders through different venues (local and regional presentations, personal communications, EDIS publications, and trade journal articles). Results from several fieldtrials are being prepared for peer-review publication. Objective 2: New experiments were initiatedin commercial and other settingsto focus on the influence of citrus rootstock on tree performance under HLB endemic conditions. Studies on the influence of rootstock propagation method on tree performance will be continued and 2-year results are being prepared for peer-review publication. <br><br><b>Publications</b><br>
Target Audience
Target audience: The target audience are primarily citrus growers and other industry stakeholders, including grove owners, grove mangers, farm operators, etc.) as well as other researchers, extension personnel, students, and the general public. Efforts: Provided science-based information in form of seminars/presentations, lectures, information handouts/printouts, posters, online access topresentations,personal communications with stake holders, scientific journal articles, trade journal articles, and EDIS publications.
Changes / Problems
Nothing Reported
Training & Professional Development
Opportunities for students and student interns were provided to learn about and assist with research activities. Lab demonstrations to the public about program research activities were provided. Participated in conferences to gain new knowledge.
Dissemination Streams
Preliminary research findings were presentedat local, regional, and national events (Research and EducationCenter presentations, Citrus Expo, Citrus Show, etc.). Findings were also discussed with growers and other industry members during personal meetings, phone calls, or emails.
Next Reporting Steps
Continue to collect horticultural data on plant performance. Continue to update stakeholders on research activities and preliminary findings through activities described above. <br><br>
<br>What was accomplished under these goals? Objective 1: Greenhouse and field studies were continued.Horticultural data collection (tree size, canopy density, foliar disese symptoms, yield, etc.) was conducted to assess plant responses to treatments and performance of different citrus rootstock varieties. Root and leaf samples were collected and processed; analyses are still ongoing. Preliminary data were presented during seminars, in trade journal articles, and other venues and are being prepared for peer-review publication. These are mult-year projects. Objective 2: New experiments were started in commercial and other settings, primarily to assess citrusrootstock performance under HLB-endemic conditions and to assess the influence of rootstock propagation method on tree performance. Horticultural data collection has been initiated. These are also multi-year projects. <br><br><b>Publications</b><br>
Target Audience
Target audience: Citrus and vegetable industry stakeholders (grove owners, growers, production managers, farm operators, scouts, etc), researchers/scientists, extension personnel, students, the general public. Efforts: Provided science based information in form of presentations, lab demonstration, hands-on research activities, lectures, printouts, online presentations, trade journal articles, scientific journal articles, EDIS publications.
Changes / Problems
Nothing Reported
Training & Professional Development
Nothing Reported
Dissemination Streams
Seminarswere held to inform citrus growers and other audience about concepts of research goals and preliminary research findings. Results were also disseminated via personal communications with growers.
Next Reporting Steps
Greenhouse and field trials will continue and experiments will be improved and streamlined based on research findings. New findings will be disseminated to the citrus community through personal communications, presentations, trade journal article, and/or other means. <br><br>
<br>What was accomplished under these goals? Objective 1.Assess effects of different types of biotic and abiotic amendments on plant physiology, growth and performance under greenhouse conditions, and develop methods for efficient screening of these substances prior to conducting longer-term field trial under commercial conditions. - Several greenhouse experiments were initiated using different citrus rootstock genotypes and different types of biotic and abiotic amendments. Horticultural data were collected and analysed. Plant tissue sampes were collected,processed, and different physiological analyses are still ongoing. Preliminary information on findings was presented at different grower and other industry seminars. New greenhouse experiments are in progress. Objective 2.Evaluate alternative management practices and their effect on citrus tree performance and elucidate the underlying physiological mechanisms associated with these effects under commercial citrus growing conditions. Alternative management practices include use of different rootstock types, different organic or other amendments, and possibly other horticultural practices. - Several field trials were initiated in collaboration with commercial growers. Differentdifferentcitrus rootstock genotypes and different types of biotic and abiotc amendments were included in these trials. Preliminary horticultural data were collected and analysed. Plant tissue sampes were collected,processed and different physiological analysesare still ongoing. Preliminary information on findings was presented at different grower and other industry seminars.Trials are still ongoing. <br><br><b>Publications</b><br>