CITRUS GREENING DISEASE (HLB) and other virus diseases such as citrus tristeza closterovirus (CTV), citrus tatter leaf cappilovirus (CTLV) and citrus exocortis viroid (CEVd) have been causing considerable damage to fruit yield and quality, and have become serious constraints for the citrus industry in the Asian and Pacific (ASPAC) region in recent decades. These systemic diseases are effectively controlled by integrated measures of disease management such as: 1) establishment of virus-free citrus cultivar repository, which is of primary importance in preventing prevalence of the diseases; 2) precise and rapid disease indexing techniques indispensable for management of pathogen-free (PF) nursery system through health certificate of PF seedlings; 3) establishment of shoot-tip micrografting technique for obtaining PF germplasm foundation; and 4) performance of health management for preventing reinfection of PF trees in the field through IPM of vector insects. These integrated techniques have been well-developed and adopted for the improvement and development of the citrus industry in Taiwan. Hence, citrus growing countries in the ASPAC look forward to Taiwan's technological support to prevent growers' losses due to citrus greening and other virus diseases.

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 activities:

• 1) Survey of citrus greening and virus disease incidence in ASPAC countries;
• 2) Conduct of technical consultation among growers on health management in the citrus-growing areas of the region;
• 3) Training-workshop on virus indexing and shoot-tip micrografting technology;
• 4) Collection and virus-elimination of the most important citrus cultivars (more than 15) selected from participating countries in the region for the establishment of pathogen-free citrus germplasm repositories to be made available to every country as a way of promoting promote regional technical cooperation; and
• 5) Establishment and management of pathogen-free citrus nursery system in the ASPAC region.

Highlights of Year 2 Implementation

On the second-year implementation of this three-year project aiming to rehabilitate the citrus industry particularly in Cambodia, the first Phytopathology Laboratory was established in the country's Royal University of Agriculture (RUA). A collaborative undertaking between FFTC, the National Taiwan University (NTU), and the Rural Development Foundation (RDF) of Taiwan ROC, a series of technical and financial support and instrument donation led to the completion of the laboratory. Following are the instruments donated to the laboratory: 1) ELISA reader; 2) Digital gel image system; 3) Force digital micro-centrifuge; 4) Dry heater-bath; 5) Quick spin; 6) Microplate shaker; 7) Micropipette; 8) Electrophoresis cabinet; and 9) Vibrator for running the laboratory.

The facility is expected to intensify RUA's research capacity to fight the devastating citrus greening (HLB) and other citrus virus diseases and train young scientists in the areas of disease indexing, production of virus-free nursery foundation, and healthy management to prevent reinfection. RUA has also completed construction of a net-house for virus-free repository and disease-free nursery production. Under the coordination and expertise of Dr. Hong-Ji Su, Professor Emeritus NTU and FFTC Technical Consultant, training on shoot-tip micro-grafting technology for virus-free germplasm foundation and propagation/cultivation of disease-free seedlings were also conducted.

Also under this project, the FFTC/NTU Training Workshop on Technology on Indexing and Production of Pathogen-free Citrus Seedlings was held in NTU, Taiwan on August 5-12, 2007. Participants to this training workshop were three researchers from the Philippines and two researchers from Malaysia. The training workshop aimed to provide the trainees with a comprehensive technical and working knowledge on citrus greening (HLB) and virus disease indexing and management toward the production of pathogen-free citrus seedlings. The said training was under the expertise and guidance of Dr. Hong-Ji Su, Professor Emeritus of NTU and FFTC Consultant.

The activity was envisioned to facilitate citrus research and development in the two countries, especially the establishment of disease-indexing laboratories in the participants' respective institutions.

Establishment of Pathogen-Free Citrus Germplasm Repository for the Improvement of the Citrus Industry in Aspac (Year 2)

This three-year (2006-2008) special project is being carried out in Taiwan ROC, Cambodia, and other ASPAC countries.

Co-sponsors:

National Taiwan University (NTU)

Rural Development Foundation (RDF), Taiwan ROC

For further information, contact:

Dr. Hong-Ji Su, FFTC Technical Consultant

Index of Images

Figure 1 Prof. Su supervises Mr. Vung Setha of RUA on the use of new instruments at the RUA Phytopathology Laboratory.

Figure 2 Prof. Su and RDF specialist Dr. Sheng-Huang Lu donate precision instruments for HLB diagnosis to RUA.

Figure 3 RUA Vice Rector Mr. Ngo Bunthan and Prof. Su practice micro-grafting techniques in the new RUA citrus net-house.

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