Germination of resting spores of Plasmodiophora brassicae

Abstract

Resting spores of Plasmodiophora brassicae Woron. were germinated in standing drops on microscope slides or in larger volumes in vials or flasks from which they were removed for examination and, when necessary, concentrated by centrifugation. Light microscopy showed that, at germination, the globules in the resting spore disintegrated and then the zoospore emerged very slowly through a small pore. Flagella appeared when the zoospore was almost free. The proportion of resting spores that germinated depended on their source and sometimes on their treatment during storage. More resting spores from old, decaying galls germinated sooner than from young, firm galls. When some spores were kept at 4 °C in dilute suspension their capacity to germinate was decreased, suggesting that a germination factor can be leached from the spores. Germination was hastened and the proportion that germinated was increased in the presence of cabbage plants or of diffusate from cabbage roots. The ionic composition of the medium also affected germination.