Studies on the Resistance of Carrot Roots to Pythium aphanidermatum (Eds.) Fitz.

Carrot roots were found to be resistant to Pythium aphanidermatumbut not to Rkizopus stolonifer. Such factors as temperatureof incubation for the inoculated hosts and pH of the host tissuedid not provide any clue to the resistance of carrot to theformer pathogen. Tests for a preformed inhibitor of pectic enzymesof the fungus in carrot, or formation of such a substance asa result of host-fungus interaction, gave negative results.The resistance was attributed to the presence of a phenoliccompound in carrot, which inhibited the growth of the former,but not of the latter. When the factor for resistance was appliedin the susceptible hosts at the site of inoculation with thefungus, the hosts showed resistance.