It has been well known that the root of Brassica rapa var. neosuguki Kitam. develops abnormally and forms a gall when the root was infected with Plasmodiophora brassicae Woronin. In order to characterize plant hormones responsible for the abnormal growth, extractions were carried out with petroleum ether, benzene, ethyl ether and ethanol successively from the infected roots. Active principle(s) were contained in benzene and ethyl ether fractions.
The active substance was not considered to be gibberellin or its like substance by the gibberellin test using rice seedlings. One or possibly two active substances were found in ethyl ether extract from the benzene fraction of the infected roots by the biological tests with Avena.
One of them was presumed to be indole acetic acid by Rf values of paper chromato-graphic analyses, and by the Avena tests.
