ALICE BEINING, HEINER GOLDBACH, JÜRGEN BURKHARDT
University of Bonn, Institute of Plant Nutrition, Germany
Because of the recently reduced profits in coffee production, cultivation area shifted to marginal sites in order to keep pace with low prices. The results are drought and temperature stress due to the extremely narrow genetic pool of the cultivars used in breeding. Consequently, breeding of coffee genotypes with improved tolerance to drought is becoming an acute issue and a more detailed understanding of the mechanism underlying drought tolerance in arabica coffee is needed.
Therefore, a study is being carried out to analyse drought tolerance strategies in four wild populations of Coffea arabica along a precipitation gradient at its place of origin and centre of diversity, in Ethiopia. There, Coffea arabica shows a wide ecological distribution as well as a certain tolerance to drought due to the dry season in this region.
It was hypothised that the rainfall gradient would create distinct selection pressures for traits related to water use and promote regional differentiation in adaptation to drought stress. In order to identify the physiological mechanisms responsible for drought tolerance (i) ecophysiological differences due to soil water availability, (ii) tolerance to progressively increased soil drying and (iii) the influence of genetic variation on any phenotypic variation observed in field grown plants is assessed.
Changes in gas exchange, water potential and carbon isotope discrimination were studied during a single year's dry and wet season. To examine variations among and within different provenances, measurements have been carried out under field conditions. The results of this study are presented.
This study forms part of the ZEF-Project ``Conservation and use of the wild populations of Coffea arabica in the montane rainforests of Ethiopia (CoCE)''.
Keywords: Coffea arabica, Ethiopia, forest coffee, water relations