Conservation genetics of wild coffee (Coffea spp.) in Madagascar.

摘要

The genus Coffea L. (Rubiaceae) consists of two economically important species for the production of the beverage coffee: Coffea arabica and C. canephora. Madagascar has 59 described species of which 42 are listed as Critically Endangered, Endangered or Vulnerable by criteria of the Red List Category system of the World Conservation Union (IUCN). The National Center of Applied Research and Rural Development (FOFIFA), the main agricultural research agency in Madagascar, manages and operates the Kianjavato Coffee Research Station which has a vast ex situ collection of various Madagascan coffee species. In an attempt to understand the genetic diversity of Madagascan coffee species, this study was undertaken using the collections maintained at the Kianjavato Coffee Research Station's ex situ field genebank and extant, natural in situ populations. As part of my dissertation, I studied four species: C. kianjavatensis, C. montis-sacri, C. vatovavyensis , and C. commersoniana. Parentage analysis of ex situ propagated offspring of C. kianjavatensis and C. montis-sacri was performed to understand if outcrossing with other Coffea species maintained in the field genebank is compromising the genetic integrity of the collection.;I found the overall genetic diversity of wild Madagascan coffee species to be similar to or even higher than other cultivated and wild Coffea species. For the three species endemic to the Kianjavato region, C. kianjavatensis, C. montis-sacri, and C. vatovavyensis, higher genetic diversity was observed in the ex situ populations than in in situ populations. For C. commersoniana, an endemic species of the littoral forests of southeastern Madagascar and soon to be impacted by mining activities in that region, the in situ populations showed higher genetic diversity than the ex situ population. Parentage analysis of seed-propagated offspring of C. kianjavatensis and C. montis-sacri revealed that cross contamination with pollen from other Coffea species in the ex situ field genebank is occurring.;These results have significant implications for the conservation management of wild Coffea species. The higher genetic diversity of the ex situ collections which were originally made in the early 1960's could be indicative of a sampling of what was present at that time and as a result of collection from multiple origins. It could also be a result of cross contamination from pollen transfer from another species resulting in hybridization when seedlings are used in replanting lost plant collections. The genetic partitioning among the two in situ populations of C. commersoniana was high enough to warrant that these two populations be kept separate for restoration purposes. Based on these findings, recommendations for conservation management are made.;This dissertation research is the first study to characterize the genetic diversity of Madagascan Coffea held at the ex situ field genebank and comparing this with extant wild populations. The parentage study is also the first to quantify the extent of cross-species contamination of collections held in this or any other Coffea genebank. This study has fundamental implications for the future of ex situ and in situ conservation of Coffea and provides a framework for future conservation research for Madagascan and other Coffea species.