**Acknowledgements**

We would like to thank Center for International Cooperation in Agronomic Research for Development (CIRAD)-Madagascar, the " Sud Expert Plantes " 381 project for their financial support. Thank you also to all the people who supported us for the realization of this field study as well as the writing of this article, in particular the service of cooperation and cultural action (SCAC), service of the French Embassy in Moroni.
