Corynespora cassiicola is a devastating fungal pathogen which causes Corynespora Leaf Fall disease (CLFD) in Hevea brasiliensis, a perennial tree crop widely cultivated throughout the Asian countries as the sole commercial source of Natural Rubber. Severity of Corynespora infection varies among different clones of Hevea. Cassiicolin, the toxin secreted by the fungus, is the primary determinant of Corynespora pathogenicity. In the present study, susceptibility/tolerance of various clones of Hevea towards CLFD, as observed in field conditions, has been confirmed in vitro. Also, a positive correlation has been established between high kitinase activity and tolerance towards CLFD. Chitinase activity was assayed in the leaves of field grown Hevea clones, belonging to both susceptible and tolerant groups. Significantly higher chitinase activity was observed in tolerant clones as compared to susceptible ones. Results from these studies open up the scope of early selection of pipeline clones tolerant towards CLFD. In vitro development of Corynespora resistant plants was attempted using callus cultures of RRII 105, the most popular and widely cultivated clone which is highly susceptible to CLFD. Embryogenic calli were cultured over medium fortified with cassiicolin. Toxin insensitive calli were selected, proliferated and again exposed to cassiicolin. Tolerant calli obtained after two cycles of selection were subcultured for further development including embryo induction and maturation. Germination of the mature embryos leading to plant regeneratio could be achieved. An initial survival rate of 20;was obtained when the regenerated plantlets were subjected to hardening. Chitinase assay was carried out using leaves from the hardened plants along with leaves of normal somatic plants of 105 as control. It was observed that the experimental plantlets showed enhanced chitinase activity compared to the normal ones, which in turn might have contributed towards the observed tolerance to CLFD. This approach opens up an avenue for in vitro development of Corynespora resistant Hevea plants.