EFFECT OF THE PERIOD OF THE YEAR WHICH EXPLANTS WERE COLLECTED ON SHOOT GROWTH AND THE CALLUS FORMATION OF THE TISSUE CULTURED JACK FRUIT

A method for rapid propagation of mature Jack fruit from apical meristem culture wasdeveloped. Apical meristems were estahlished in Modified Campbell and Durzan mediumsupplemented with NAA and ISA. Cultures were suh cultured in every 4 weeks interval inorder to reduce the accumulation of phenolic compounds. Reducing the accumulatedphenolics at the base of the explant enhanced the growth rate. There was a significantdifference in the growth performance of shoots and callus produced according to the periodof the year in which explants were collected.60% of the apical meristems cultured in modified CD medium supplemented with IBA andNAA produced shoots in November to December period. It was only 30% when the apiceswere cultured in April to May months and decreased to 20% in June - July months. Theshoots produced in November - December period showed a higher vigour (in number ofleaves per shoot. mean leaf width and mean shoot length) than those produced in othermonths. Since jackfruit show seasonal changes in fruit bearing and shedding of leaves. itcan be suggested that the difference in growth performances of tissues cultured in artificialculture media would have been effected by endogenous rhythms. It has been observed thatthe callus production depends on the incubation temperature. Callus was induced at thebase of the shoot hy increasing the incubation temperature from 2S± IIIC to 30± Ifie.Growth of the callus was also retarded hy accumulated phenolic compounds in themedium.