IN-VITRO SELECTION FOR HIGH-TEMPERATURE TOLERANCE IN CULTURED SHOOT EXPLANTS OF PINUS-CARIBAEA MORELET

Selection of tolerant plants is the first step towards the production of plants adapted for growth in stressed environments. An attempt was made to select heat stress tolerant Pinus caribaea via tissue culture from explants originating from four provenances. The explant performan ce was evaluated using data on explant height and extent of leaf necro sis. The population structure of provenances was markedly altered by s election pressure imposed by high temperature. At 35 degrees C, variat ions in growth were significant between explants within a provenance b ut not between provenances. At 37 degrees C, variation in growth becam e significant between provenances also. This variation in performance of provenance explants may be attributed to the native temperature ran ge experienced by a provenance. An improvement in explant performance at 37 degrees C was also observed in those provenances which had been pre-conditioned at 35 degrees C over unconditioned controls.