Zoosporangia, believed to be those of Plasmodiophora brassicæ, in the Root Hairs of Non-cruciferous Plants

Abstract

IN 1936, during work on the cytology of P. brassicæ, zoosporangia identical with those of this well-known parasite were seen by me in root hairs of grass and dock seedlings, which had appeared in a pot of soil taken from a garden in which the club root disease of the Cruciferse was a major problem. In view of the known persistence of P. brassicæ in soils without cruciferous crops, it was decided to attempt a crude cross-inoculation experiment using club root galls as a starting point. Suitable soil was partially sterilized by keeping it at 190° F. for one hour. Ten six-inch pots were filled with this soil, and club root galls with unbroken surfaces, but of an age known to contain mature spore masses, were cut up and placed in five of them. Brussels sprout seedlings germinated in these pots became infected, and an examination of the root hairs of the grass Holcus lanatus grown from seed with them in the re-infected soil revealed numerous zoosporangia and some free-swimming zoospores.