Performing Department
EXPERIMENT STATION
Non Technical Summary
Major crops in American Samoa are multiplied by vegetative propagation. This method is slow and can spread existing pests and disease. Susceptible crops either grow poorly and yield less, or must be treated with pesticides. The Plant Tissue Culture Laboratory can rapidly multiply disease-free plants, including new resistant varieties. Growing these plants can reduce pesticide use, lower production costs, and protect workers and the environment.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
We propose to reopen the Plant Tissue Culture Laboratory (PTCL) at the American Samoa Community College Land Grant facility, closed since 1999. We have four goals, or long-term objectives, for the PTCL. 1) Mass propagate important traditional and introduced plants, including new disease resistant taro and banana hybrids. Almost all fungicide used in American Samoa is applied to the Cavendish-type banana cultivar 'Williams' for control of black leaf streak disease (BLS). Resistant hybrids from international breeding programs, such as Fundacion Hondurena de Internacional Agricola (FHIA), are grown without fungicides and could replace the BLS-susceptible 'Williams'. American Samoans commonly increase their plantations by removing and replanting the suckers. When a new cultivar is introduced for the purpose of improving the industry, the small number of initial plants makes this practice unworkable; it takes too many years to produce an acceptable number of plants. In the
PTCL, new introductions can be multiplied exponentially by micropropagation, producing thousands of plantlets per year. 2) Limit transfer of pests and diseases on-island and across quarantine barriers by exchanging disease-free tissue culture plantlets. Insects and disease challenge the most sophisticated quarantine procedures. In vitro plantlets, however, are usually disease-free when indexed for systemic diseases. In American Samoa, banana bunchy top virus disease and banana root nematodes are spread within and between farms by planting infected suckers. Using micropropagated plantlets to establish new fields could reduce the occurrence of these diseases. New varieties of leaf blight resistant taro from islands with certain virus diseases not present in American Samoa have been unavailable, but virus-indexed tissue culture plantlets could be safely imported. 3) Develop new micropropagation procedures for multiplying tropical plant species difficult to propagate by seed or other
vegetative means. Traditionally, plants difficult to propagate by seed or cuttings had to be grafted. Micropropagation offers the opportunity to clone these plants on their own roots. Habitat destruction from a rapidly increasing population is changing the plant palette in American Samoa. Native trees and shrubs needed for revegetation projects, and traditional and medicinal plants for practice of the Samoan cultural arts, are often in short supply. Difficulty propagating some of these species in the usual manner could lead to their loss from the local flora. Our non-commercial, research-oriented PTCL will have the ability to pioneer new techniques for difficult to propagate tropical plant species. 4) Preserve rare, threatened, or endangered plant species in a living germplasm collection. Species extinction has increased a thousandfold, with one species evolving for every 1,000 that cease to exist. Taro 'Niue', a favorite Samoan variety, was almost exterminated by taro leaf blight
disease (TLB) in 1993. Preserving taro Niue in vitro may allow eventual transfer of its unique genes for taste and consistency to a TLB-resistant hybrid, either by traditional breeding or through genetic engineering.
Project Methods
The following procedures support the broader objectives discussed above: 1) In order to open and operate the PTCL, the Manager will clean, disinfest, and reorganize the facility. She will order the media and fresh supplies of inorganic salts, vitamins, carbon sources, and plant growth regulators necessary to run the laboratory. The Manager will perform basic tissue culture procedures to test the cleanliness of the laboratory environment and confirm its readiness for micropropagation. By the end of the first year, a research assistant will be hired and trained by the PTCL Manager in plant tissue culture techniques. 2) The PTCL Manager will obtain a permit from the American Samoa Department of Agriculture to import new taro breeding lines from the Regional Germplasm Centre, Secretariat of the Pacific Community (SPC), Suva, Fiji. The plantlets will be received in the multiplication stage, ready to divide. After multiplying the plantlets in a solid medium high in salts and
low in plant growth regulators, they will be potted in a sterile soil mix and moved to a greenhouse mist bench for acclimatization. After 2-3 months, plants will be distributed to selected growers for evaluation. Explants will be excised from the most popular line(s), multiplied again, and offered to American Samoan farmers. 3) In order to increase worker safety, protect the environment and increase farmer profits, the PTCL will micropropagate banana hybrids resistant to black leaf streak disease. These hybrids will be supplied by the SPC under the auspices of the International Network for the Improvement of Banana and Plantain (INIBAP) in Heverlee, Belgium. The procedure, from multiplication to distribution, will be similar to that for taro (see #2) except the multiplication medium is semi-solid, lower in salts, and higher in plant growth regulators. The number of plantlets multiplied will depend on grower response to these hybrids, as it will with the taro lines. 4) We will
establish field trials for evaluation of micropropagated taro and banana (see #2, #3) for disease resistance, cultural characteristics, and flavor. Due to limited land and poor security, only a small number of resistant taro and banana hybrids can be planted for testing and demonstration at the Land Grant Station. A Memorandum of Agreement will be signed between the ASCC Land Grant Program and participating banana farmers wanting to grow BLS-resistant plants; this includes an increasing number of organic growers. A similar Memorandum will be written for taro growers based on the one used for the Samoa Taro Improvement Program (TIP). In this successful program established in 1999, growers are provided with new breeding lines and procedures for planting and evaluating them. In return for their cooperation, American Samoan growers will keep all plant material and their recommendations will influence selection of lines for further multiplication in the PTCL (see #2).