Overview Objectives

This project aims to improve our knowledge of the genetic variation existing in selected species of mangroves, and then to produce and disseminate germplasm of high quality varieties. The work is expected to benefit mangrove conservation and reforestation in South and Southeast Asia.

Project Background and Objectives

Mangrove forests are a well known feature of coastlines in the tropics and subtropics. They are very important in protecting and stabilising coasts in cyclone-prone areas. They act as a nursery for many fish species of economic importance and a habitat for other fauna. They can also be an important resource for local people, providing them with wood and other products. Mangroves are now heavily exploited in many parts of the world. Wood-gathering and fishpond operations are the main threats. Other pressures are mining and mineral extraction, diversion of freshwater (which damages mangrove roots), the development of coastal areas with associated silt and pollution, the construction of channels and harbours, and the disposal of wastes.

About 80 higher plant species, from several different groups, are considered as mangroves. There is thus considerable variety in mangrove forests. This diversity is generally reduced by exploitation or other damaging pressures. Once damaged or destroyed, it is hard to re-establish mangrove forests. The survival rate of seedlings is naturally low, and this difficulty is compounded by a lack of seed availability to establish re-planting programs. It’s also important to know what types of mangroves to plant where. If reforestation of degraded mangrove areas is to be successful and appropriate conservation strategies defined, it will be necessary to improve the collection, storage and transport of mangrove germplasm (the seeds) and to understand better the intricacies of mangrove genetics.

Several developing countries have asked ACIAR to help with the problem of obtaining adequate supplies of desirable germplasm to set up mangrove plantations. These requests were the origins of this project.

Progress Reports (Year 1, 2, 3 etc)

Outcomes to December 2002

After two and a half years excellent progress had been made in achieving the objectives related to the application of DNA marker techniques to the mangrove Avicennia marina. This research was conducted at Southern Cross University, and was given a head start when important groundwork for the molecular studies of genetic diversity in this species was initiated and supported by Southern Cross University in 1997. The results have been disseminated in several publications in refereed journals, and have raised important questions about population structure, mating systems and gene flow that are currently being addressed in Australia (A. marina) and Thailand (R. apiculata). In Thailand, the collaborators have succeeded in establishing new techniques of DNA analysis with support and training from Southern Cross University. The project has thus clearly contributed to building research capacity in Thailand.

Glasshouse trials of A. marina from different provenances have shown that plants maintain differences in morphological and growth characters when grown in the same environment. This is an important result as it demonstrates that these traits are genetically determined. It still needs to be determined what characteristics are considered desirable for re-establishment of new plantations in specific locations, and the extent to which these can be sought out in natural populations.

A major aspect of the project has been to develop micropropagation of mangroves using tissue culture techniques. However, it has become evident that mangroves (A. marina and Rhizophora spp.) do not respond well in tissue culture. Satisfactory progress has been made at Burringbar NSW and Yen Lap, Vietnam, yet much work remains ahead before routine and efficient micropropagation of desirable genotypes can be achieved.

1. A microsatellite library has been established for Avicennia marina (Maguire et al. 2000a) in order to be able to characterise the genetic variation that exists within and between populations of this species. The results indicate that microsatellites are abundant in the Avicennia marina genome and can be valuable genetic markers for assessing gene flow in mangrove communities.
2. Microsatellite analysis of the genetic structure of this mangrove has also been undertaken (Maguire et al. 2000b) , based on six Australian (Qld, NSW, Vic, SA, WA and NT) populations and on populations from South Africa, United Arab Emirates, India, Japan, Malaysia, Papua New Guinea, New Caledonia and New Zealand. This analysis strongly indicated that there was considerable genetic diversity between the various populations of this species and that gene flow was very limited between them. In addition, many populations have “private alleles” i.e. unique alleles found only in the one population.
3. It has been established that the distances germplasm naturally moves through pollen and propagule dispersal is in the order of Laura’s main outputs. This has important implications when considering introducing non-local germplasm for maintenance or enhancement of natural genetic diversity in restoration programs.
4. A comparative study of AFLP (Amplified Fragment Length Polymorphisms) and SSR (Simple Sequence Repeats or Microsatellites) techniques for analysis of genetic diversity in Avicennia marina has shown that either, or a combination of both techniques, is applicable to expanded studies of mangroves (Maguire et al. 2001). SSRs are particularly suitable for population-based investigations. AFLPs are more suitable for monitoring propagation programs and identifying duplicates within collections.
5. Output 2. has had some influence amongst mangrove managers in Australia. The QLD Department of Primary Industry now require that to conserve genetic integrity mangrove regeneration sites should only use propagules produced in the same catchment as the regeneration area.
6. It has been established that differences in growth characteristics seen in Avicennia marina from different parts of Australia has a genetic (genotype + genotype/environment interaction) rather than an environmental basis (Walker et al. 2005 submitted).
7. A technique for dissecting and establishing the growing seedling from mangrove seeds in aseptic culture was devised to successfully provide enough plant material for investigative media trials. This method is also successful through all the stages of tissue culture to produce a healthy potted plant. Although it does not involve an increase in numbers, it could provide large numbers of plants for field plantings at specified times such as outside the typhoon season in Vietnam.
8. A successful protocol for the micropropagation of Avicennia marina from both seed-derived explants and field-derived explants was developed. The only drawback with this protocol is the multiplication rate which is at best X 2 and the success at plant-out. Both very common problems with woody species.
9. Callus can be induced from specimens of anthers and ovaries, propagules and mature leaves of Avicennia marina. However, callus inducing specimens are still small in quantity and the callus induced suffered from a slow growth rate.
10. The natural distribution of Rhizophora apiculata has been surveyed in the Gulf, East and South of Thailand.
11. Development of a microsatellite library for R. apiculata has commenced.
12. Development of AFLP markers for R. apiculata has commenced.

Project Outcomes

Mangrove communities have been heavily exploited for their wood, and disturbed by other activities including aquaculture, mining, and disposal of chemical wastes. This project was established with Thailand to undertake molecular biological studies on genetic variation in mangroves, and Vietnam to develop methods for micropropagation of mangrove through tissue culture.

After two and a half years excellent progress was made in achieving the objectives related to the application of DNA marker techniques to the mangrove Avicennia marina. This research was conducted at Southern Cross University, and was given a head start when important groundwork for the molecular studies of genetic diversity in this species was initiated and supported by Southern Cross University in 1997. The results have been disseminated in several publications in refereed journals, and have raised important questions about population structure, mating systems and gene flow that are currently being addressed in Australia (A. marina) and Thailand (R. apiculata). In Thailand, the collaborators have succeeded in establishing new techniques of DNA analysis with support and training from Southern Cross University. The project has thus clearly contributed to building research capacity in Thailand.

Glasshouse trials of A. marina from different provenances have shown that plants maintain differences in morphological and growth characters when grown in the same environment. This is an important result as it demonstrates that these traits are genetically determined. It still needs to be determined what characteristics are considered desirable for re-establishment of new plantations in specific locations, and the extent to which these can be sought out in natural populations.

A major aspect of the project has been to develop micropropagation of mangroves using tissue culture techniques. However, it has become evident that mangroves (A. marina and Rhizophora spp.) do not respond well in tissue culture. Satisfactory progress has been made at Burringbar NSW and Yen Lap, Vietnam, yet much work remains ahead before routine and efficient micropropagation of desirable genotypes can be achieved. The project has received an 18-month extension.

Project ID
FST/1994/019
Project Country
Commissioned Organisation
Southern Cross University, Australia
Project Leader
Professor Peter Saenger
Email
psaenger@scu.edu.au
Phone
02 6620 3631
Fax
02 6621 2669
Collaborating Institutions
Royal Forest Department, Thailand
Vietnam National University, Vietnam
Project Budget
$866,940.00
Start Date
01/07/1999
Finish Date
30/06/2002
Extension Start Date
01/07/2004
Extension Finish Date
31/10/2005
ACIAR Research Program Manager
Dr Russell Haines
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