improvement of resistance to pythium ultimum in safflower by selection under field conditions

damage of the pathogens is one of the main limitations for cultivating and production of safflower. this study was performed to investigate reaction of safflower genotypes to pythium ultimum during 2009 and 2010 under field conditions. the study was done in two parts, selection and evaluation of parents (part 1; 2009) and evaluation of the progenies (part2; 2010). in the first year, the experiment was performed as a randomized complete block design including selected seeds (seeds obtained on plants at infested soil) and unselected seeds (obtained seeds at sterilized soil) of 6 genotypes in 8 replications. in the second year, experiment was conducted in 3 different conditions. these conditions were included of two infested environments (environment 1 and 2) and one sterile environment. the suspension of 105 per ml zoospore was used for infection. results showed that p. ultimum damping-off decreased speed of emergence. selection increased percent of emergence of genotype zargan from 29.25% to 40.75%, of syrian from 37.0% to 46.0% and of 34074 from 41.7% to 64.2%. improving of percent and speed of emergence in infested soil with p. ultimum showed that selection is an effective way for breeding resistance to this disease in some of safflower genotypes.