evaluation of safflower genotypes to find genetic sources of resistance to damping-off (pythium ultimum)

damping-off is an important disease of safflower in iran, that caused by pythium ultimum. because of its importance, fungi isolates were sampled from infected plants grown in research farm of the college of agriculture, gorgan university of agricultural sciences and natural resources, in 2006. also it has been proved that the disease caused by pythium ultimum. evaluation of seventeen safflower genotypes (zarghan-259, arak-2811, isfahan, syrian, dinger, hartman, aceteria, cw-74, lrv-55-295, lrv-51-51, iutm12, pi-250537, il-111, 34062, 34074, 34040 and 541-5) for their response to causal agent were performed in 2007. the experiment was conducted in paper towel environment was done as split plot design in a complete randomized blocks in which two environments (sterile and infected) were included as main plot and also seventeen genotypes were as sub plot in four replicates. artificial inoculation was conducted with 105 per ml oospore suspension of fungi agent. in sterile media percent and speed of seed germination and also dry weight of seedling and in infected media percent, real percent and speed of germination, number of infected seedlings and number of non-germinated seeds was recorded. results showed that there was significant difference among the genotypes for all evaluated traits and also for reaction to disease. comparison of means indicated that genotype dinger with 79.7% had the highest real germination in infected media, and genotypes 34062 and isfahan with 24.4 and 14.2 % were in the next rank in this regard, respectively. the lowest diseased seedling in infected media were belonged to il-111 (6.3 seedlings), 34062 (6.8 seedlings) and dinger (8.3 seedlings), respectively. overall, the results of this study showed that some of non-iranian genotypes were a good source for resistance to damping-off. additionally, some of iranian genotypes in respect to seed germination and related parameters were weak, however for resistance to the disease were superior to others. so, genotypes dinger, isfahan and 34062 could be used in breeding program of safflower to produce cultivars with resistance to damping-off.