College of Plant production, Gorgan University of Agricultural Sciences and Natural Resources, P.O. Box 386, Gorgan, Iran.
One of the major field constraints to seed production in safflower has proven to be soil born pathogens, Phytophthora drechsleri and Pythium ultimum. In order to evaluate the efficiency of a field-laboratory selection method to improve resistance of safflower against soil born pathogens, Ph. drechsleri and P. ultimum, a two-year investigation was conducted. The results showed that selection is an efficient method for increasing resistance to seed and seedling death caused by Phytophthora and Pythium in safflower. Selection could have improved germination percent, days to 50% germination, percent of undamaged seedlings and index of disease percent when genotypes were faced with both pathogens. Regarding kind of damages, Pythium caused more seed rot and Phytophthora induced more seedling death. It could be concluded that selection for resistance to Pythium, could also increase resistance to Phytophthora. Safflower was, however, more susceptible to Phytophthora than Pythium. Also, genes for resistance to seed rot are different than those controlling resistance to seedling death, so preemergence damping off should be considered a completely independent trait from post-emergence damping off in safflower. It was concluded that used fieldlaboratory selection method could well improve resistance of safflower to pathogens Phytophthora and Pythium and hence seed yield.