Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 204 - Plant Product Quality and Utility (Preharvest) | 999 - Citrus, general/other | 1060 - Biology (whole systems) | 100% |
One of the main challenges that the Citrus Industry faces in Florida is HLB. The disease has decimated citrus acreage and fruit production by 70% in the last years. Currently there is no cure, and viability of the Citrus in Florida is compromised by rising production costs and shrinking crop every year. The Industry is in need of immediate solutions that increase productivity (lowering costs and increase in yield and quality) until a viable long term solution is found.To help growers through science-based solutions aimed at prolonging the productive life of citrus trees while maximizing fruit yield and quality, I will adopt different approaches. Theseinclude assaying and evaluating novel therapies against disease, studying performance and productivity of new citrus varieties with an emphasis in fresh fruit production from the selections available through UF and USDA Breeding Programs, and assessing root health in citrus trees to help growers to fine tune nutrition and save costs. Results from this research will assist growers in managing newly planted varieties, fine-tune nutrition to improve root system health and increase yield of better quality fruit, which ultimately will result in reduction of production costs and increase in benefits.
The citrus industry is the largest tree fruit industry in the Southeast, with more than 400,000 acres in production, and $10.5 billion in annual revenues. However, under prevalent Huanglongbing (HLB) conditions, Florida citrus growers are in need for ready-to-apply, effective, and inexpensive new strategies to mitigate HLB as well as to improve productivity of existing mature citrus trees and enhance health in novel plantings.Citrus Huanglongbing (HLB), is the most economically devastating disease of citrus worldwide and the most important challenge that Citrus Industry is facing. In Florida, the disease is caused by the fastidious gram-negative α-proteobacteria Candidatus Liberibacter asiaticus (CLas) and since first detected in 2005 it has reduced the citrus acreage and fruit production by 70%. Currently there is no cure, and disease management consists of controlling psyllid vector with regular insecticide applications, removal of infected trees, elimination of affected groves, and enhanced nutrition programs for improving plant health of infected trees. However, results are not consistent in neither enhancing tree health and fruit yield and quality nor stopping or slowing infection rate, and now it is estimated that more of 80% of Florida citrus acreage is infected. A long lasting solution will be the development of citrus cultivars resistant to disease through engineering, and strategies based on overexpression of pathogenesis related protein PR1 have shown some promise (Dutt et al., 2015). However, a viable engineered solution is far from approval for commercial adoption, and the industry is in need of shorter-term effective solutions. Currently, Florida growers are investing heavily on nutritional, insecticide and antibiotic programs. The cost per acre has doubled in a decade from approximately $900 to $1,800 and continuation of management effort at this level is not sustainable. In addition, fruit quality for both fresh market and juice is compromised by the disease, which reduces the profits further.The general objective of this project is to increase benefits of citrus growers through understanding physiology associated with the interface between new treatments against disease, new varieties and new growing techniques that ultimately will impact horticultural behavior of citrus trees grown in Florida. Specific objectives are:
To address these questions and provide science-based answers that will make a positive impact for growers in Florida, three different strategies will be adopted in my Program:
PROCEDURESIn general, field trials will be performed at SWFREC and commercial citrus production groves.Objective 1. Field trials will be set up at least at four different location within the citrus growing regions of Florida. Field trials will be set up with collaboration of citrus growers under commercial production practices. Data will be collected before treatments and at every 4 months for disease index rating, CLas quantification, canopy volume and density, flush pattern, photosynthesis, starch accumulation, root density and longevity, leaf nutrient level, and gene expression analysis. Total yield, pre-harvest fruit drop and fruit quality data will be collected.Objective 2. This objective has two sub objectives. In the first one, I will research on how nutritional status of the nursery-grown tree prior to planting in the grove will influence behavior. Different sets of plants subjected to disparate growth conditions in the greenhouse (mimicking those standard conditions performed by different nurseries in Florida) will be then planted in the grove at SWFREC for monitoring tree performance under environmental pressure. Data on Gas exchange (stomatal conductance and photosynthesis), Chlorophyll fluorescence (to measure the integrity of the photosystem), Stem caliper, Number of mature leaves, Leaf area, as well as molecular root stress indicators, will be monitored periodically. Also, CLas bacteria titer after planting and at the end of the year will be measured at the HLB Detection Lab Service at SWFREC.The second sub objective will study the seed germination from different rootstock seed sources highly demanded by Florida citrus industry. This will include fruit maturity, to determine when the fruit is ready to bear viable seeds, and assessment of germination rate. Fruit maturity (internal and external) will be monitored periodically and seeds extracted and then transferred to agar tubes to quantify germination potential.Objective 3. The evaluation trial of novel promising varieties will be performed in the SWFREC grove. 5 acres of land have been allocated for this Objective. After detailed discussion withrepresentatives from the Industry, including South West Florida Citrus Advisory Committee, a selection of promising rootstock and scion combinations from the UF and USDA breeding programs has been made and will be planted. This is part of a larger evaluation project involving also CREC and IRREC.Objective 4. This objective potentially interacts with the other three. Phospholipase enzymatic activity and gene expression of all 5 PLD-encoding genes expressed in roots will be monitored after challenging citrus trees with different nutritional deficiencies. By doing so we will be able to determine minimum micronutrient thresholds for gene expression change in the root. Gene expression will be monitored by real time-RT-PCR and phospholipase activity will be analyzed by spectrofluorometry.
Target Audience
-Citrus growers -County Extension Agents -General public -Master Gardeners -Legislators (State representatives and associated offices)
Changes / Problems
We still had to adjust our work schedule to covid restrictions. Some data collection was impacted by these restrictions and even covid impacting some personnel in my lab
Training & Professional Development
This has resulted in participation of me and my graduate students in the annual meetings of the ASHS and FSHS during 2021 to present results from our research, several invited talks, and 2 In Service Trainings at UF.
Dissemination Streams
-7 presentations in professional meetings -11 presentations/extension seminars -4 articles in trade journals -6 articles in EDIS -5 peer reviewed papers -1 Book chapter
Next Reporting Steps
Objective 1. We will focuse on identifying pathways involved in resistance to pests that is induced by the homobrassinolide treatment. Objective 2. We will continue the work to determine maximum viability of seeds after cold storage and we will report the results in a paper. Objective 3. We will continue to study the efficacy of IPCs attending to different citrus varieties. We will search for ways to prolongue the protective effect of IPCs once they are removed. We will assess quality and yield of fruit prodiced in trees covered by IPCs as they enetr into the producing age. Objective 4. We will fine tune treatments with zink and potassium to maximize fruit yield and minimize fruit drop in Hamlin and Valencia. We will determine the best timing for these treatments, as efficacy varies during the fruit development.
Target Audience
-Citrus growers -County Extension Agents -General public -Master Gardeners
Changes / Problems
This year has been marked by restrictions due to COVID situation and the impossibility for months to access remote grove experimental settings and also entering the lab at UF. This has resulted in delays in all my projects.
Training & Professional Development
This has resulted in participation of me and my graduate students in the annual meetings of the ASHS and FSHS during 2020 to present results from our research.
Dissemination Streams
-4 articles in Citrus Industry magazine -14 talks to growers and stakeholders in workshops and events including Citrus Show and Citrus Expo, and a virtual talk to Extension agents at University of Puerto Rico. -5 EDIS papers -3 peer reviewed papers
Next Reporting Steps
Nothing Reported
<br><br>
<br>What was accomplished under these goals? Objective 1. We are continuing the assessment of the effect of homobrassinolides at 4 different commercial sites in Florida (Central and South) and in our farm at SWFREC. We are regularly collecting data and performing treatments in the installed experimental sites. Objective 2. After identification of reliable markers for seed maturity, we have been able advance rootstock fruit harvesting and seed extraction from October-November to August and has allowed to increase seed production up to 20% in the very demanded US942 rootstock. We are continuing now with the study of viability of these seeds after cold storage and we have determined that seeds harvested in August can undergo at least 2 months of cold storage without losing viability. A paper describing these results is currently in preparation. Objective 3. After planting new trees from 4 different varieties of mandarins and round oranges, including SugarBelle, Early Pride, Tango and Bingo both in the open field and also under CUPS, and using individual protective covers (IPCs) we are continuing studies of performance of these varieties under these completely different growing strategies. One manuscript has been submitted for publication, and a Masters thesis is close to completion this year. Objective 4. We are continuing the study on the effect of different nutrients with emphasis on potassium and zink, since they are linked to root hair elongation and fruit drop in the field and also in an in vitro system. Initial data show that combined treatment of both nutrients reduces fruit drop significantly, so this strategy has the potential to increase fruit yiled under HLB endemic conditions <br><br><b>Publications</b><br>
Target Audience
-Citrus growers -County Agents -General public
Changes / Problems
Nothing Reported
Training & Professional Development
This has resulted in participation of me and my graduate students in the annual meetings of the ASHS and FSHS to present results from our research
Dissemination Streams
-4 articles in Citrus Industry magazine -SWFREC Annual Open House
Next Reporting Steps
Nothing Reported
<br><br>
<br>What was accomplished under these goals? Objective 1. We are assessing the effect of homobrassinolides at 4 different commercial sites in Florida (Central and South) and in our farm at SWFREC. Experimental sites have been installed and treatments and data collection have started. Objective 2. We have identified markers for seed maturity. This is allowing to advance rootstock fruit harvesting and seed extraction form October-November to August and has allowed to increaes seed production up to 20% in some varieties. Currently we are studying viability of these seeds after cold storage. Objective 3. We have planted new trees from 4 different varieties of mandarins and round oranges, including SugarBelle, Early Pride, Tango and Bingo both in the open field and also under CUPS and using individual protective covers. we are comparing performance of these varieties under theses completely different growing strategies. Objective 4. We have started to study the effect of different nutrients with emphasis on potassium and zink, since they are linked to root hair elongation and fruit drop in the field and also in an in vitro system. <br><br><b>Publications</b><br>