Quantitative estimation of spore germination of Plasmodiophora brassicae

Ungerminated resting spores of Plasmodiophora brassicae may be simply and successfully stained by 1% orcein dissolved in 45% acetic acid. Germinated spores fail to absorb this stain and in consequence are distinguished from non-germinated ones using conventional light or Nomarski Interference Contrast microscopy. Numbers of germinated spores and primary zoospores were strongly correlated indicating the accuracy of this technique as a means of estimating germination levels.