Under this three-year special project, to rehabilitate the citrus industry in ASPAC countries, an advanced Taiwanese technology package will be transferred first to Cambodia, and then to other countries in the region. The technology package shall include establishment and application of pathogen-free citrus foundation, and disease-indexing technique for controlling serious epidemic of citrus greening (HLB) and other virus diseases. Specifically, the project shall have the following acvitivities:
Citrus greening (HLB) and other virus diseases have been devastating citrus production in Cambodia, and has become a serious epidemic, affecting over 80 percent in some orchards of Pursat orange. The HLB disease also infects pummelo trees, giving rise to low quality fruits. The first year implementation of this special project focused on the case of Cambodia as a major citrus-growing country in the region devastated by HLB and other virus diseases. The project objectives specific to Cambodia for year 1 were as follows:
In August 2006, a survey team visited citrus areas in Battambang Province in Cambodia. The Pursat cultivar of sweet orange is being cultivated in Banon area of Battambang. The fruit quality of Pursat orange was acceptable to the people, and growth of the trees were well-adapted to the environment. However, most of the Pursat orchards were seriously affected by greening disease. The team noticed that the HLB disease has been seriously devastating sweet orange orchards in the area. Some pummelo trees showed greening symptoms, indicating that the strains of HLB pathogen in Cambodia have evolved into strain I, which mainly attacks mandarin and sweet oranges, and strain II, which has been infecting mandarin, sweet orange and pummelo cultivars. The team collected leaf tissues for disease indexing. They also visited the Siem Reap areas for citrus orchards and inland aquaculture on the north coast of Tonle Sap Lake. HLB-infected trees of Pursat and Mexican lime were identified in some citrus orchards in the suburban Siem Reap. Disease indexing of citrus materials from Cambodia were done, and PCR patterns were obtained.
The systemic HLB and CTV diseases are mainly transmitted through vegetatively propagated seedlings, and spread by vector insects in the field. Accordingly, establishment of indexing techniques, pathogen-free citrus foundation, and nursery system are of primary importance in combating the disease epidemics.
The Royal University of Agriculture (RUA) of Cambodia seeks to establish indexing laboratory and pathogen-free citrus foundation repository in the university in order to rehabilitate the citrus industry in the country from the epidemic devastation. Two scientists from Cambodia had the opportunity to learn basic techniques of disease indexing and shoot-tip micro-grafting at the Plant-Virus Laboratory of the National Taiwan University (NTU).
This international collaboration will be implemented for the second year, with the following specific objectives: establishment of HLB-virus indexing techniques, laboratory, and citrus foundation; construction of insect-proof screenhouse repository for citrus foundation, and production of pathogen-free foundation via shoot-tip micro-grafting; and production of pathogen-free citrus seedlings with excellent and potential cultivars selected from locally-adapted Pursat orange, tropical mandarin, and pummelo cultivars.
Initial preparations are now ongoing for the establishment of a disease indexing laboratory in RUA. The indispensable instruments for the activities mentioned above, will be prepared through the assistance of the Rural Development Foundation (RDF) of Taiwan ROC. Meanwhile, the diagnostic kit/probes (virus-antibodies and PCR-primers) and reagents shall be provided by NTU. A land next to the laboratory is secured for the construction of a screenhouse repository. Seedlings of citrus root-stock have already been grown in pots in a simple net-cover stand, in order to accelerate the production of pathogen-free citrus foundation and seedlings for field demonstration.
This three-year (2006-2008) special project will be carried out in Taiwan ROC, Cambodia, Vietnam, Laos, and other ASPAC countries.
Co-sponsors: National Taiwan University (NTU)
Rural Development Foundation (RDF), Taiwan ROC
Figure 1 The Survey Team Visited a Pursat Orange Orchard Seriously Affected by the Greening Disease in Battambang Province, Cambodia. <B>(Inset)</B> a 5-Year-Old Orange Tree Showing Greening Symptoms.
Figure 2 Visit to Pursat Orange Orchard Affected by Greening Disease in Siem Reap Area, Cambodia. <B>(Inset)</B> Diseased Pursat Branch Showing Typical Yellow-Mottling Symptoms.
Figure 3 Growing of Root-Stock Citrus Seedlings in Pe Pots Inside Simple Insect-Proof Net Covers at the Royal University of Agriculture (Rua), Cambodia.
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