Special projects

Health management of

pathogen-free (PF) citrus seedlings for the rehabilitation of the citrus industry from serious epidemic of HLB and virus diseases in the Philippines (Year 1)

Citrus is one of the mos important fruit crops worldwide consumed as fresh fruit and further processed into other value-added products. However, citrus systemic diseases of greening (Huanglongbing or HLB), and viruses such as Citrus tristezaclosterovirus (CTV), Citrus tatter leaf cappilovirus (CTLV) and Citrus exocortis viroid (CEVd) have become serious constraints for the citrus industry in the Asian and Pacific (ASPAC) region in recent decades, causing considerable damage to fruit yield and quality. This is due to their systemic invasion and common spread through infected budwood, vegetatively propagated seedlings, and transmission by insect vector and by mechanical means. These major systemic diseases can only be effectively controlled by integrated measures of disease management such as: a) rapid diagnostic and indexing of virus strains; b) establishment of pathogen-free (PF) foundation and nursery system to prevent primary prevalence of the diseases; and c) healthy management of the PFseedlings re-planted in terms of field sanitation and IPM of vector insects.

In the early 1990s, FFTC launched a technology transfer project to transfer Taiwan's advanced technology to rehabilitate the devastated citrus industry in Vietnam. Since then, the project has been expanded to various Asian countries, most recently to Cambodia. However, citrus HLB disease continues to devastate citrus orchards in the region, and has particularly become a serious constraint for the citrus industry in the Philippines. Through this project, PF citrus foundation and nursery system will be established in the Philippines, together with disease indexing techniques and the necessary facilities/equipment. Health management of PF seedlings which are re-planted in the orchards is envisioned to be the keyfor the successful rehabilitation of the citrus industry in the country.

Other Southeast Asian countries such as Myanmar and Laos also need to adopt this integrated technology to rehabilitate their own citrus industry. Therefore, it is a matter of urgency to extend this technology transfer project on the mass production of PF citrus seedlings and their healthy management to these countries.

Technology transfer highlights

The training program including lecture and exercises in wide spectrum containing epidemiological natures of Huanglongbing (=HLB citrus greening) and citrus viruses, pathogen-indexing, production and health management of pathogen-free citrus seedlings was instructed by Prof. Hong-Ji Su and his colleague at the Virus Laboratory of NTU. The disease indexing course was concentrated to practice the RT-PCR (reverse transcription PCR) for detecting citrus tatter-leaf virus and exocortis viroid which were possibly existing in South-east Asian countries, and affecting fruit yield and quality of citrus trees rooted on stocks of Runpure lime, trifoliate and its hybrid cultivars Establishment of pathogen-free citrus foundation and seedling production have been primarily important for the management of HLB and virus diseases through shoot-tip micrografting technique which was intensified for instruction purposes.

An additional seminar on health management of PF citrus orchards was held in Chiayi Agricultural Experiment Station (CAES), COA for the trainees and local technical parsons, totally of about 25 participants. Dr. Shih-Cheng Hung of CARI gave a talk on IPM of citrus insect vectors transmitting HLB and viruses, and Dr. Cha-Shin Tsai presented his thesis on chemotherapy of citrus HLB by antibiotic injection of trees. The concerning topics were enthusiastically discussed by participants and speakers since the health management of PF citrus seedlings was the last key-point task of HLB & virus disease control.

The trainees were guided to the national PF citrus foundation screen house of CARI for observing our well established PF citrus foundation stocks which were serving the sources of producing PF seedlings national wide. The participants made a trip to citrus orchards in Chiayi area. They learned and practiced the techniques taught to them regarding the establishment of pathogen-free nursery system, indexing techniques and health management of PF citrus seedlings.

Healthy management of pathogen-free (PF) citrus seedlings for the rehabilitation of the citrus industry from serious epidemic of HLB and virus diseases in the Philippines (Year 1)

Project type: Technology transfer

Dates and venue: 2011-2013 (year 1: Jan-Dec. 2011,

Philippines)

Implementing agency: Department of Agriculture-Bureau

of Plant Industry (DA-BPI)

For further information, contact Prof. Hong-Ji Su, FFTC Technical Consultant

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