Abnormal growth of tissues infected with Plasmodiophora brassicae.

Abstract

SUMMARY Clubroot formation on Sinapis alba plants infected with Plasmodiophora brassicae was not prevented by application of 2,3,5-triiodobenzoic acid or α-naphthylphthalamic acid (inhibitors of polar transport of auxins in plants) to the hypocotyls. However, the fresh weight of club tissue produced on treated plants was lower than on untreated plants. This difference in weight was of the same order as the difference in total fresh weights of treated and untreated plants. Explants of tumour tissue from two Brassica species infected with P. brassicae, unlike explants from healthy roots, produced callus on a tissue culture medium without growth substances. Callus growth from infected tissues depended on the presence of active vegetative plasmodia in the cells. Established clones of Brassica rapa (Golden Ball) callus infected with vegetative plasmodia of P. brassicae, unlike healthy callus clones, grew well on a series of media deficient in one or more growth substances. Growth of infected Golden Ball callus on medium without growth substances was prevented by the tryptamine antagonist xylamidine tosylate and by the monoamine oxidase inhibitor iproniazid. Inhibition was annulled by including abnormal growth of Brassica roots infected with P. brassicae is discussed.