Progress 09/01/10 to 08/31/13
Outputs
Target Audience:Targeted audience was (and will continue to be) primarily citrus growers that would benefit directly from the developed HLB diagnostic test. Furthermore, citrus researchers in Florida, Puerto Rico and from around the world can also benefit from the effectiveness of the developed test. Targeted audience was (and will continue to be) primarily citrus growers that would benefit directly from the developed HLB diagnostic test. Furthermore, citrus researchers in Florida, Puerto Rico and from around the world can also benefit from the effectiveness of the developed test. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?The project provided for the training of a MS student for 2 years until his graduation. In addition, the grant facilitated for the travel and presentation by the graduate student of the findings of this research. How have the results been disseminated to communities of interest?Results have been published in refereed and non-refereed journals. They have also been presented at scientific meetings. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
One of the most prominent characteristics of huanglongbing (HLB or citrus greening)-affected citrus trees is the abundant starch accumulation in photosynthetic cells and all other remaining parenchyma cells of aerial parts. Under natural conditions, citrus leaves store very low levels of starch and detectable amounts are only seen as a result of zinc deficiency or accidental girdling of branches. Therefore, leaf starch concentrations over a threshold level should indicate the presence of HLB. In this report, we detailed a comprehensive statistical analysis of starch levels in citrus leaves and compared them with real-time polymerase chain reaction (PCR) detection of the presumptive causal agent Candidatus Liberibacter asiaticus. Starch content was found to reliably predict the PCR results (the proxy for HLB presence) during the ''warm season'' (June through November) but not in the ''cool season'' (December through May). During the cool season, starch levels for HLB-positive trees tend to be lower, and 43% of samples were incorrectly classified using Linear Discriminant Analysis (LDA). In contrast, during the warm season, only 8% were misclassified. Furthermore, assuming PCR possibly has error, the total probability of misclassification for HLB status could be controlled using an ''uncertain'' classification. The temporal pattern of leaf starch is consistent with our understanding of seasonal changes in plant development and bacterial titer.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Whitaker, D.C., M.C. Giurcanu, L.J. Young, P.Gonzalez, E. Etxeberria, P. Roberts, K. Hendricks, F. Roman. 2014. Starch content of citrus leaves permits diagnosis of Huanglongbing in the warm season but not cool season. HortScience 49:757762.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
1. Whitaker, D., Giurcanu, M.C., Young, L.J., Gonzalez, P., Etxeberria, E., Roberts, P., Hendricks, K., Roman, F. 2014. Starch content in citrus leaves: A test with seasonal accuracy. Phloem anatomy of Citrus trees. Healthy vs. greening-affected. Proc. Fla. State Hort. Soc. 12675-83.
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Progress 09/01/12 to 08/31/13
Outputs
Target Audience: Target audience includes extension agents, research scientists, and most importantly citrus growers from all citrus growing states. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The project offered a training opportunity for an OPS HS graduate individual who worked in the project for 2 years. How have the results been disseminated to communities of interest? Results were disseminated in three basic ways. At horticultural conferences by means of talks and posters At growers meetings Through scientific journals What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Determine the range of leaf starch content in healthy and HLB –affected leaves throughout Florida. Over 1,000 leaf samples from seemingly healthy and HLB-affected trees were taken and analyzed for both starch content and CLas titer using PCR. Samples were taken from all citrus growing counties in Florida plus Puerto Rico. Leaf samples were analyzed for starch at the UF facilities in Lake Alfred using a rapid method involving iodine, whereas PCR was conducted at the HLB diagnostic facilities in SWFREC, Immokalee. Both analyses were conducted with the same set of leaves. Data were analyzed using a variety of methods described in various publications. Starch content was found to reliably predict the PCR results (the proxy for HLB presence) during the “warm season” (June through November), but not in the “cool season” (December through May). During the cool season, starch levels for HLB positive trees tend to be lower, and 43% of samples were incorrectly classified using Linear Discriminant Analysis (LDA). In contrast, during the warm season, only 8% were misclassified. Further, assuming PCR possibly has error, the total probability of misclassification for HLB status could be controlled using an “uncertain” classification. The temporal pattern of leaf starch is consistent with our understanding of seasonal changes in plant development sand bacterial titer. The developed technique is effective in all citrus producing areas indiscriminately. There doesn’t seem to be differences between geographic locations as are with seasons.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Whitaker, D.C., Giurcanu, M.C., Young, L.J., Roman, F., Roberts, P., Hendricks, K., Gonzalez, P., Etxeberria, E. 2013. Starch content in citrus leaves: A test with seasonal accuracy. Proc. Florida State Hort. Soc. 126: (In Press)
- Type:
Journal Articles
Status:
Accepted
Year Published:
2014
Citation:
Whitaker, D.C., Giurcanu, M.C., Young, L.J., Roman, F., Roberts, P., Hendricks, K., Gonzalez, P., Etxeberria, E. 2014. Starch Content of Citrus Leaves Permits Diagnosis of Huanglongbing in the Warm Season but not Cool Season. HortScience, In press
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Gonzalez, P., Reyes-De-Corcuera, J., Etxeberria, E. 2012. Characterization of leaf starch from HLB-affected and unaffected-girdled citrus trees. Physiological and Molecular Plant Pathology 79:71-78
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: During the phase of experimentation and data analysis, there has not been any dissemination of the project. Information has only been communicated to several extension agents and specialists until it is published. PARTICIPANTS: This project was carried out with the participation of several State agencies and with the collaboration of various growers. The research collaborating institutions were University of Florida's Citrus Research and Education Center, UF Southwest Research and Education Center, UF IFAS Statistics Department, University of Puerto Rico-Mayaguez, and various growers around the state. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The detailed completion of the project was instrumental in delaying the potential worldwide implementation of an HLB test based on starch content. In this project, the results indicate that there is uncharacterized variability in the detection of the bacteria Las (HLB causing agent) that prevent a direct correlation between PCR detection and starch content. The data collected included over 1,000 samples from around the state of Florida analyzed for both presence of bacterial DNA and starch content. The data was thoroughly analyzed statistically before reaching any conclusion. The resources provided by the granting agency were instrumental for the completion of the project.
Publications
- No publications reported this period
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: The project aimed at investigating the possible development of an inexpensive and rapid test for HLB using starch accumulation patterns observed in infected citrus trees commenced with the assembly of a team to gather all pertinent information. The project was design and sample collection and analysis started in November, 2010, and data are being analyzed. Data collection will continue for one year. Samples from collaborators in Puerto Rico have also been collected and processed accordingly. Meanwhile, the second goal of the project consisting of examining the potential interference by other citrus diseases in the determination of starch induced by HLB was completed. Samples of trees infected by other diseases such as tristeza, phytophtora, blight and CTV were investigated. PARTICIPANTS: This project involves personnel from the University of Florida and University of Puerto Rico. The PI team is completed by Linda Young from IFAS Statistics (UF) and Felix Roman from the University of Puerto Rico. An OPS was hired and in charge of sample collecting and analysis. TARGET AUDIENCES: The eventual audience is the citrus industry of Florida and Puerto Rico. The main outcome of this project, if successful, will develop a test for HLB to be used throughout the industry. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Most of sampling and data collection is under way. However, with samples from diseased trees it was determined that no other disease induces starch accumulation in citrus leaves therefore not posing a potential interference for the development of a starch-based test for HLB. This finding is of great significance since starch, being a natural product, could have presented some irreparable problems if its accumulation were enhanced by other conditions. Therefore, we have concluded so far that starch can be used as a detection tool for HLB. The remaining project is aimed at setting the boundaries that will determine between a healthy from a diseased tree.
Publications
- No publications reported this period
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