EVALUATION OF BIOCHEMICAL MARKERS (SUGAR, PROLINE, MALONEDIALDEHYDE AND ETHYLENE) FOR COLD SENSITIVITY IN MICROCUTTINGS OF 2 COFFEE SPECIES

Microcuttings of coffee (Coffea arabica L. and Coffea canephora Pierre) were conserved in vitro for 0-20 weeks at various temperatures (12, 17, 22 and 27-degrees-C). Survival was generally high, except for C canephora stored at 12-degrees-C. After a transitory increase in fructose and glucose concentration at the beginning of the storage period, the sugar level remained stable. During the first weeks of storage, the quantity of proline increased to twice the initial level for both species at 12-degrees-C. A drop in the proline concentration was observed with C. canephora at the end of the storage period at 12-degrees-C. Whereas in the case of C. arabica, no modification was noted in the malonedialdehyde (MDA) concentration, its level increased in microcuttings of C. canephora stored at 12-degrees-C. This increase was reversible after 10 days at 27-degrees-C at the beginning of the storage period, but became irreversible after a 20-week storage duration. Ethylene production started after transfer to 27-degrees-C after a 2-week storage period with C. canephora, but after 12 weeks only in the case of C. arabica. This synthesis decreased at the end of the storage period for C. canephora microcuttings stored at 12-degrees-C. These results indicate that among the four compounds studied, MDA appears as the most reliable indicator of cold sensitivity for the two coffee species studied.