Articulo Biotecnologia

EJB Electronic Journal of Biotechnology ISSN: 0717-3458 © 1998 by Universidad Católica de Valparaíso –- Chile

Vol.1 No.3, Issue of December 15, 1998. Received 28 July 1998 / Accepted 14 August 1998

REVIEW ARTICLE

Medium-term and long-term in vitro conservation and safe international exchange of yam (Dioscorea spp.) germplasm
Bernard Malaurie 1
GeneTrop – Unité de Génétique etd’Amélioration des Plantes - Centre ORSTOM** – 911 avenue Agropolis - BP. 5045 -F. 34032. Montpellier Cedex 1, France. Tel: Bureau (33)-- 4 67 41 62 44 Tel: Standard (33)-- 4 67 41 61 00 Fax: (33)-- 4 67 54 78 00 E-mail : Bernard.Malaurie@mpl.orstom.fr

Marie-France Trouslot
GeneTrop – Unité de Génétique et d’Amélioration des Plantes - Centre ORSTOM** – 911 avenue Agropolis - BP. 5045 -F. 34032.Montpellier Cedex 1, France. E-mail : Bernard.Malaurie@mpl.orstom.fr

Julien Berthaud
GeneTrop – Unité de Génétique et d’Amélioration des Plantes - Centre ORSTOM** – 911 avenue Agropolis - BP. 5045 -F. 34032. Montpellier Cedex 1, France. E-mail : Bernard.Malaurie@mpl.orstom.fr

Mustapha Bousalem
Laboratoire de Phytovirologie des Régions Chaudes (LPRC) – CIRAD-ORSTOM** – avenue du val de Montferrand -BP. 5035 -F. 34032 - Montpellier Cedex 1, France. E-mail : dubern@melusine.mpl.orstom.fr

Agnès Pinel
Laboratoire de Phytovirologie des Régions Chaudes (LPRC) – CIRAD-ORSTOM** – avenue du val de Montferrand - BP. 5035 -F. 34032 - Montpellier Cedex 1, France. E-mail : dubern@melusine.mpl.orstom.fr

Jean Dubern
Laboratoire de Phytovirologie des Régions Chaudes (LPRC) – CIRAD-ORSTOM** – avenuedu val de Montferrand - BP. 5035 -F. 34032 - Montpellier Cedex 1, France. E-mail : dubern@melusine.mpl.orstom.fr http://www.mpl.orstom.fr

Yam edible tubers feed million of peoples in the intertropical area, where they represent 12% of human feeding. However, as a vegetatively propagated crop, yam is seriously affected by an accumulation of pathogens. Establishing in vitro germplasm collectionis a process that cleans the plants from all diseases but viruses. It gives a good control on the preservation of the yam genetic resources and facilitates international exchanges of healthy plant material. Two kinds of in vitro germplasm preservation were considered : slow growth condition culture for midterm preservation, and cryopreservation using the encapsulation/dehydration technique forlong-term preservation. Virus eradication was approached by meristem culture and chemo and thermotherapy. Production of virus-free plants was controlled by ELISA.

We succeeded in the introduction and maintenance of 20 yam species, under slow growth conditions. Cryopreservation was applied successfully on two edible yam species, Dioscorea. alata L and D. bulbifera L. Virus-free plants were obtainedby meristem culture in D. cayenensis-D. rotundata complex and D. praehensilis. Indexation allowed the detection of different virus (poty-, potex-, badna- and cucumovirus), where the most important potyvirus was YMV. Mid-term conservation of yam germplasm is used routinely, and from these conditions a direct acclimatization is possible. On the cryopreservation aspect, experiments are under way toapply the optimized protocol to genotypes which are more representative of the diversity, to insure a routinely use. More work can be conducted now on virus eradication,

1 Corresponding author ** ORSTOM is now called IRD, Institut de Recherche pour le Developpement.

This paper is available on line at http://www.ejb.org

Malaurie B., Trouslot M-F., Berthaud J., Bousalem M., Pinel A. andDubern J.

based on knowledge accumulated on potyvirus diversity, on several tests available for yam indexing (ELISA, rt/PCR, monoclonal antibodies) and on new sanitation techniques.

Yam belongs to Dioscorea genus which has more than 600 species (Coursey, 1967) most of them distributed in the intertropical humid area. We will distinguish two types of yam: 1) medicinal yams, 2) edible yams...