[Synopsis] Tissue culture was used for selecting and enhancing the resistant variant cells which indigenously exist in leaf tissues of the susceptible cultivar in order to establish an efficient system for producing crown-rot resistant lines of strawberry. Leaves of the resistant and susceptible cultivars were inoculated with the crown-rot pathogen by needle-prick inoculation method. Two types of lesions (small necrotic spots and extensively expanding lesions) were formed on leaves of both the resistant and susceptible cultivar. The resistant cultivar was characterized by higher percentage of the small necrotic spots. The cells forming the resistant-type lesion were amplified by inducing callus tissues from leaf explants of the susceptible cultivar, and regenerants showing the higher frequencies of the resistant-type lesion were selected. The amplification of these cells to the level of the resistant cultivar was achieved by repeating callus induction and plant regeneration from the selected repenerants. The regenerants finally obtained in the present system showed the resistance in the field inoculation test
