Strategic Planning for the Florida Citrus Industry Addressing Citrus Greening Disease (2010) / Chapter Skim
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3 Citrus Greening Research and Development and Industry Preparedness
3 Citrus Greening Research and Development and Industry Preparedness
Pages 67-92
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From page 67... ...
Finally, we summarize the history of funding support for pest management and for citrus research and development generally and the importance of establishing communication channels for citrus researchers. An inventory of HLB research projects that are ongoing can be found in Appendix J and a list of HLB research milestones from 1956–January 2009 is provided in Appendix K
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From page 68... ...
. Obtaining the CLas genome sequence has added to our knowledge of HLB, but how this information can contribute to HLB mitigation remains to be demonstrated.
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From page 69... ...
Among the separate plots, the numbers of PCR-identified infected trees was well correlated with the total number of infected trees, R2 = 0.89, suggesting a natural progression of infected but asymptomatic trees to symptomatic trees. Although the average CLas titer in asymptomatic trees was significantly less than the titer in symptomatic trees (M.
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From page 70... ...
. Spectral differences have been detected in comparisons of healthy and HLB-affected citrus using detached leaves and leaves of intact citrus trees (Mishra et al., 2007; Tilling et al., 2007; Lee et al., 2008; Poole et al., 2008)
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From page 71... ...
. The Citrus Transcriptome The citrus genome sequence, when it becomes available, will provide a list of all of the candidate genes of the citrus tree and the complete amino acid sequences for almost all of the proteins those genes encode.
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From page 72... ...
RESEARCH SUPPORTING CURRENT HUANGLONGBING MITIGATION PRACTICE: REDUCING ASIAN CITRUS PSYLLID ACCESS TO CITRUS Suppression of ACP by Insecticide Application Currently much effort is being expended by university, government and private industry researchers with the goal of developing new, more effective and safer insecticides and insecticide application technologies. Equally important is the goal of maintaining the effectiveness of valuable insecticides by delaying or avoiding the appearance of insect resistanct to the insecticide.
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From page 73... ...
Thus, the concept of SIT uses continued releases of highquality sterile males to overwhelm wild-type males over successive generations and result in progressively reducing the indigenous population to levels of extinction. If SIT can be developed for a pest, it is the key component of an area-wide integrated pest management program.
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From page 74... ...
The citrus trees themselves may exhibit symptoms of HLB , and the number of HLB-affected citrus trees increases as the mixed orchard reaches three to four years of age. The high ratio of guava trees to citrus trees needed to achieve protection does not seem compatible with current Florida citrus production, but guava trees could find application in orchards following the Advanced Citrus Production System (described below)
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From page 75... ...
Registration will be costly and may require from 8 to more than 55 months, but could result in an elegant short-term form of HLB mitigation. Trap plants have been proposed for use in conjunction with feeding repellents of ACP compounds such as DMDS in a "push-pull" strategy to concentrate ACP populations into a zone for eradication by insecticide application.
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From page 76... ...
The push-pull strategy has been considered as a component of an area wide ACP-HLB management program. HUANGLONGBING EPIDEMIOLOGY AND ASIAN CITRUS PSYLLID BEHAVIORAL ECOLOGY There remains a great need for more information on HLB epidemiology under Florida conditions; such information could provide the basis for creation of management/mitigation programs or regulatory programs in the state.
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From page 77... ...
Such compounds could lead to new ACP management strategies. Vector-pathogen Interactions Information on CLas transmission rates and CLas effects on ACP is needed to provide the foundation for epidemiological models and predictions of HLB spread and other HLB
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From page 78... ...
and sexual transmission are vector-pathogen phenomena that could influence HLB epidemiology. Experimentally demonstrating transovarial or sexual transmission requires care to insure that plant hosts for rearing ACP are CLas-free or non-susceptible (Purcell, 1982)
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From page 79... ...
A dominant gene for resistance to Citrus CTV is known in Poncirus trifoliata, and species highly resistant to citrus canker, in calamondin, kumquat and Ichang papeda also exist. However, there is little or no evidence for genetic resistance to HLB in Citrus or related genera and a survey in South African orchards, where HLB has been present for decades, failed to identify any HLBdisease resistant trees (Roux and Grout, Citrus Research International, Nelspruit, South Africa, personal communication)
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From page 80... ...
. TABLE 3-1 Major Citrus Species that have been Genetically Transformed to Produce Citrus Plants with Genes of Agronomic Interest Common Name Scientific Name Gene Introduced Reference Carrizo Citrus sinensis × Citrus blight-associated Kayim et al., 2004 citrange gene Poncirus trifoliata Carrizo C
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From page 81... ...
Peña and colleagues have transferred this material and the procedure to São Paulo State, Brazil, where they have produced mature transgenic citrus trees expressing antibacterial peptides, which now are under evaluation. A critical factor in mature citrus transformation is collection of
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From page 82... ...
Because mature tissue transformation is not yet available in Florida and juvenile citrus transformation is more efficient and less cultivar specific than mature citrus transformation, a project on accelerating the production and commercialization of transformed juvenile citrus is also being developed. Several approaches have been taken to minimize or eliminate the problem of juvenility.
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From page 83... ...
Therefore, there is a potential for using RNAi as a control measure for psyllids, and projects taking this approach are in progress. Essential genes for psyllid development or viability could be chosen for RNAi in citrus trees.
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From page 84... ...
Usually, use of bacterium- or virus-mediated gene expression is termed "transient expression" because the longer term, multi-generational gene expression characteristic of genetic engineering is not observed. It is the good fortune of citrus research, and possibly the citrus industry, that W.O.
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From page 85... ...
In summary, the advantages of the CTV-vector approach, in comparison to the transformation procedures for the production of transgenic trees from juvenile or mature tissues, are: A CTV-vector would allow CLas-resistant trees to be available in much less time than would be required for production of transgenic trees from juvenile or mature citrus tissues. If one or a few trees that are supporting the vector containing the beneficial gene for HLB control become available, the vector construction can be transferred to other citrus trees using vector-infected budwood or rootstock in the nursery or orchard.
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From page 86... ...
Based on reports that imidacloprid can induce systemic acquired resistance (SAR, described above) to citrus canker and because of its intensive use for psyllid control in newly planted citrus trees, there is interest to determine whether imidacloprid is able to induce SAR against HLB.
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From page 87... ...
, another unit of USDA, also provides funding citrus research infrastructure and personnel. These include the Center for Plant Health Science and Technology (CPHST)
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From page 88... ...
For example, Southern Gardens Citrus has planted the first research field trials of potential canker and greening disease-resistant citrus trees in its Hendry County citrus groves. The trees, noted to be resistant to canker and greening in the laboratory, were planted in small plots to determine if the trees are disease resistant under commercial grove conditions.
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From page 89... ...
Greening Research Task Force formed the Greening Research Oversight Committee to start development of a comprehensive Research Management Plan. In early January 2008, representatives of the Florida citrus industry formed an ad-hoc committee to determine a strategic research plan for dealing with HLB in Florida.
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From page 90... ...
in 2008, which was the core of what was envisioned in the diagram above. The stated objective of the program is "to apply new technologies to improve the profitability of the Florida citrus industry".
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From page 91... ...
The great benefit of colocation of researchers, as well as good communications with a wide array of researchers at other sites, may be seen from the experience with the investigation of maize stunting disease in the southern edges of the corn belt. As reported in Chapter 2, citrus research in Florida includes efforts at two major centers, the University of Florida's Citrus Research and Education Center (CREC)
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From page 92... ...
Research and development communication on Pierce's disease research is also greatly facilitated through a contract from the CDFA with the University of California's Public Intellectual Property Resource for Agriculture (PIPRA)
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