Coffee seed conservation biology: Fundamental aspects and practical implications. A review

Abstract

Since the early 1990s, the coffee seed has been designated by several international laboratories as the model system for studying the physiology of seeds of the "intermediate" category. In contrast to orthodox seeds, longevity of which increases when they are dehydrated and stored at low temperature, intermediate seeds are only partially tolerant to desiccation and low temperatures. In the narrow ranges of water contents and temperatures which can thus be used, the longevity of intermediate seeds remains very short, which constitutes a major limitation for the conservation of the biodiversity of these species. The development of new analytical chemistry techniques made it possible to demonstrate that the poor longevity of coffee seeds was associated with several types of cellular damage : neutral lipid hydrolysis leading to the accumulation of free fatty acids which destabilize membranes, selective loss of a class of phospholipids, loss and oxidation of the two major hydrophilic antioxidants, ascorbic acid and glutathione. Thanks to the knowledge gained on the processes involved in coffee seed ageing, we propose for the first time in this paper highly accurate technical recommendations for the preparation and the short-term storage of seed lots. Meanwhile, through biophysical approaches including differential scanning calorimetry, the understanding of the mechanisms involved in coffee seed tolerance to ultra-low temperature exposure has significantly progressed. Based on this knowledge, a very effective cryopreservation technique has been developed for coffee seeds, facilitating the long-term conservation of Coffea genetic resources.