Volume 2 Part 1 September 1995

Brief overview of IPGRI's research activities on in vitro conservation of plant species

Florent Engelmann
IPGRI, Via delle Sette Chiese 142, 00145 Rome, Italy

The International Plant Genetic Resources Institute (IPGRI), previously known as IBPGR, is an autonomous international scientific organization operating under the aegis of the Consultative Group on International Agricultural Research (CGIAR). IPGRI's mandate is to advance the conservation and use of plant genetic resources for the benefit of present and future generations. IPGRI works in partnership with other organizations, undertaking research, training and the provision of scientific and technical advice and information. IPGRI has four major strategic objectives: strengthening national programmes, contributing to international collaboration, improving strategies and technologies for conservation and providing an international information service.

IPGRI's structure comprises five Regional Groups which are responsible for the Institute's work in Sub-Saharan Africa; West Asia and North Africa; Asia, the Pacific and Oceania; the Americas; and Europe. In addition to the Regional Groups and Headquarters in Rome, Italy, IPGRI hosts three Thematic Groups. They are responsible for developing and coordinating research and information work of inter-regional or global relevance in their respective subject areas, and for providing scientific and technical support to the regions. The three Thematic Groups are Genetic Diversity; Germplasm Maintenance and Use; and Documentation, Information and Training.

The Germplasm Maintenance and Use Group covers the development of strategies and technologies of conservation and use, germplasm management, seed, pollen and in vitro conservation and germplasm health. The aim of this paper is to present a brief overview of the Group's activities in in vitro conservation.

Seeds of a number of species, predominantly tropical or subtropical, belong to the recalcitrant or intermediate categories and thus have a limited longevity which renders their long-term conservation impossible. For species which do not produce seeds or are predominantly vegetatively propagated, conservation in seed form is impossible or has limited application. The most common method of preserving the genetic resources of these species is as plants in the field. There are, however, several serious problems with field genebanks, such as exposure to attacks by pests and diseases, natural hazards, high labour costs for maintenance of collections, and restriction of germplasm exchange due to risks of disease transfer. The use of in vitro culture techniques, including slow growth and cryopreservation, represents an important additional option for the conservation of these problem species.

In vitro culture techniques permit the multiplication and storage of plant germplasm under aseptic conditions, with reduced space requirements due to the small size of explants, and with limited labour costs. For short or medium-term storage, plant material is placed under slow growth conditions which allow for increased intervals between transfers. For long-term storage, cryopreservation, i.e. storage at ultralow temperature (liquid nitrogen, -196°C) is the only current method. At this temperature, all cellular divisions and metabolic events are stopped. The plant material can thus be stored without alteration for extended periods, with limited maintenance. Other important applications of tissue culture techniques are collection of plant material under field conditions, and international exchange of germplasm.

IPGRI's research activities include the development of existing conservation techniques for additional species and their large-scale utilization, the development of new conservation techniques, and more fundamental studies of biological mechanisms related to conservation.

Projects focusing on the conservation of species with recalcitrant seeds are being carried out in Malaysia and in India. In FRIM (Forest Research Institute of Malaysia, Kepong) the research programme aims at developing cryopreservation techniques for excised embryos of dipterocarps. The tolerance to desiccation of embryos of seven different dipterocarp species has been assessed. In 1995, a new project will focus on the development of in vitro techniques for collecting dipterocarp germplasm in field conditions. Research on cryopreservation techniques for tropical fruit trees is being performed in UPM (Universiti Pertanian Malaysia, Serdang). The efficiency of desiccation and encapsulation/dehydration techniques is evaluated. At NBPGR (National Bureau of Plant Genetic Resources, New Delhi, India), a three-year research project funded by UK Overseas Development Authority (ODA) studied the biological mechanisms determining the recalcitrance of seeds of tea (Camellia sinesis ), cacao (Theobroma cacao) and jackfruit (Artocarpus heterophyllus) Development of seeds and embryos of these three species were accurately described and several biochemical and physiological processes relating to desiccation sensitivity were studied. New and relevant information has been provided on desiccation limits of intact seeds and embryonic axes at various developmental stages, on their tolerance to cryopreservation and on the structural damages caused to them by desiccation and freezing. Under this project, cryopreservation of partially desiccated embryonic axes of tea and jackfruit was achieved. This represents the first report of successful cryopreservation in the case of tea, and only the second in the case of jackfruit. This project ended in March 1994. A new ODA-funded project started in April 1995 aims at performing large-scale experiments and establishing a pilot cryopreserved collection of embryonic axes for jackfruit (Artocarpus heterophyllus ), and at developing cryopreservation techniques for additional recalcitrant species, lychee (Litchi sinensis), breadfruit (Artocarpus altilis), almond (Prunus dulcis) and vegetatively propagated crops, sweet potato (Ipomoea batatas ) and yam (Dioscorea spp.).

Several IPGRI projects focus on in vitro conservation of vegetatively propagated species. In Cuba, researchers at CNIC (Centro Nacional de Investigaciones Cientificas, Havana City) are refining and extending the cryopreservation technique developed for sugarcane (Saccharum officinarum) apices. More than ten Cuban sugarcane varieties have already been successfully cryopreserved and the stability of plants regenerated from frozen material is being investigated. In INIFAT (Instituto de Investigaciones Fundamentales en Agricultura Tropical, Santiago de las Vegas) a project aims at establishing a cryopreservation protocol for banana and plantain (Musa spp.).

Another project aiming at refining cryopreservation techniques for potato (Solanum tuberosum) is carried out in Braunschweig, Germany, in collaboration with DSM (Deutsche Sammlung von Mikroorganismen und Zellkulturen) and FAL (Institut für Pflanzenbau, Bundesforschungsanstalt für Landwirtschaft). This project is funded by the German Government (BMZ). It was initiated in 1991 and has been extended for two additional years. An efficient freezing technique has been set up for apices of in vitro plantlets and successfully applied to more than 80 potato varieties. Future activities include the assessment of genetic stability of cryopreserved material, freezing of additional varieties and transfer of the technique to CIP (Centro Internacional de la Papa, Lima, Peru) which has the mandate for conservation of the potato world collection.

Medium-term conservation using slow growth is addressed through another ODA-funded project carried out at the School of Biological Sciences, University of Birmingham, UK, in collaboration with the Laboratory of Tropical Husbandry, Catholic University of Leuven, Belgium, and IITA (International Institute for Tropical Agriculture, Ibadan, Nigeria). It aims at evaluating the possibility of using RAPD to detect off-types of banana and plantain generated in vitro. It has already been clearly demonstrated that the RAPD approach provides the possibility of using the information generated for the purposes of taxonomy or identification. Candidate bands which allow discrimination between normal plants and off-types have been found for several varieties.

In 1994, IPGRI also funded training periods in laboratories in France and the UK for two Cuban researchers and one Indian researcher, in order to acquaint them with new cryopreservation techniques.

Several other project proposals in the area of in vitro conservation are at different stages of advancement. IPGRI can also provide assistance on matters related to in vitro conservation, such as advice on equipment and distribution of specialised literature.

For any further enquiries on IPGRI in vitro activities, please contact:

Dr. Florent Engelmann
In Vitro Conservation Officer, IPGRI
Via delle Sette Chiese 142
00145 Rome, Italy

Tel: (39-6) 58892224, Fax: (39-6) 5750309

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