CRYOPRESERVATION OF SEEDS OF 4 COFFEE SPECIES (COFFEA-ARABICA, C-COSTATIFRUCTA, C-RACEMOSA AND C-SESSILIFLORA) - IMPORTANCE OF WATER-CONTENT AND COOLING RATE

In the range of water contents studied (0.1-0.4 g H2O g dw(-1)), Coffe a arabica seeds were less sensitive to desiccation than C. costatifruc ta, C. racemosa and C. sessiliflora seeds. At 0.20 g H2O g dw(-1), 53% of C. arabica seeds germinated after direct immersion in LN (rapid co oling, 200 degrees C min(-1)), but none of them developed into normal seedlings. By contrast, in C. costatifructa, C. racemosa and C. sessil iflora, when seeds were dehydrated to the optimal water content (0.19, 0.28 and 0.31 g H2O g dw(-1), respectively), the percentages of seeds which developed into normal seedlings after LN exposure were 26, 78 a nd 31% of the desiccation control, respectively. Normal seedlings coul d be recovered from cryopreserved C. arabica seeds only if they were d esiccated to 0.20 g H2O g dw(-1) and precooled slowly to -50 degrees C prior to immersion in LN. Precooling seeds at 2 degrees C min(-1) all owed 25% of seeds to develop into normal seedlings. The thawing rate h ad no effect on the survival of cryopreserved C. arabica seeds. In all cryopreservation experiments, the total germination did not reflect t he percentage of seeds which developed into normal seedlings. Examinat ion of excised embryos indicated a partial explanation of this differe nce since only the shoot apex was destroyed in abnormal embryos, where as the hypocotyl and radicle were normal.